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Castration and Cryptorchid Surgery
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Castration and Cryptorchid Surgery NEAL ASHTON
Castration of the Male Horse Indications for Castration Removal of the testes (also referred to as gelding, cutting, orchiectomy, orchidectomy) is routinely performed on male horses not intended for breeding purposes. The primary reason is to prevent stallion behaviour, which is generally regarded as inappropriate for most equestrian disciplines. In the wild, stallions organise into two distinct social groups: the harem bands that have one stallion and several mares, and the all male bachelor bands. Stallions can remain manageable if they remain in bachelor mode; however, interaction with other horses frequently results in harem band behaviour with increased aggression and reproductive drive (Klingel 1982). The average age that colts reach puberty is 69 weeks (range 55–101) (Cornwell et al. 1973). Stallions can be safely castrated at any age; however it is mostly undertaken at 6 months to 2 years of age. Some owners prefer to delay castration until after puberty to allow masculine features such as a crest or increased muscle mass to develop. In cattle, castration before puberty results in an increase in adult height due to delay in long bone growth plate closure (Shahin et al. 1992). It is possible that this also happens in the horse, but it is not documented or a reason for requesting castration by owners. Recently, there appears to have been an increasing tendency to castrate older animals once they have become unmanageable or once they have failed to perform to a level that justifies their use for breeding. The anatomy of the reproductive organs, in particular the penis of the stallion, is shown in Fig. 21.1 and a diagram of the testes Fig. 21.2.
Surgical Techniques Careful consideration of the age breed and type of horse, the premises at which the surgery is to be performed, and the methods for analgesia/anaesthesia should be made before selecting the surgical technique to be used. There are two broad surgical techniques, namely: (a) open castration (Fig. 21.3A–I) or (b) closed castration. An additional technique can be used in which an open castration is performed, and is subsequently closed; this prevents the possibility of postoperative herniation of abdominal viscera (Fig. 21.4 A–I). For an open castration, the vaginal tunics are incised, allowing direct visualisation of and access to the testicular vessels and the
ductus deferens, which may then be ligated and crushed or solely crushed with an emasculator; the tunics are left open after removal of the testes (see Figs 21.3 A–I). For a closed castration, the vaginal tunics are not incised, with haemostasis ensured by placing ligatures around the spermatic cord (or transfixing ligatures); in this way no opening is created into the peritoneal cavity. For the open and subsequently closed technique (see Figs 21.4 A–I), the following procedure is performed: after opening the tunic, the blood vessels and ductus deferens are ligated and transaction, and the vaginal tunic and skin are subsequently closed.
Standing Castration Standing castration (see Figs 21.3 A–I) can be undertaken in any colt that has normally descended testes, is large enough in height to enable the surgeon to access the scrotum by reaching underneath the abdomen, and has been well-handled with an amenable temperament. Owners should be warned about the risk of complications as they have been reported to occur in up to 60% of cases (Rosanowski et al. 2018). The technique is traditionally used in thoroughbred racehorses in the UK but is less popular in sports horses and warm bloods. There is anecdotal evidence that warm bloods are more prone to scrotal hernia, and this may be the reason for this difference. Standing castration is generally performed using the open technique using emasculators and without placing ligatures across the vessels and ductus deferens. The major disadvantage of this technique is the possible risk of uncontrolled haemorrhage occurring and that it does not prevent the risk of evisceration of abdominal contents through the inguinal canal because the vaginal tunic is left open. However, the internal and external inguinal rings are not in alignment in the standing horse, and so the risk appears to be less compared with when the procedure is performed in the recumbent anaesthetised animal, when herniation may occur as the animal rises to a standing position. The colt is first sedated, commonly using an α-2 adrenoceptor agonist (such as detomidine HCl) in combination with butorphanol tartrate; this results in profound sedation (Fig. 21.3A). The handler and surgeon remain on the left side of the colt, and the animal is made to stand against a wall on its right side. The surgeon approaches the scrotum from the horse’s shoulder to reduce the chance of being kicked if the colt/stallion suddenly and unexpected kicks out with his left hind leg. The right (furthermost) testis is grasped in the left hand so that it is pushed down firmly into the scrotum. An 18-gauge 40 mm needle is advanced in one swift 349
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movement perpendicular to the skin of the scrotum directly into the testis to the level of the needle hub. Once the needle is in position, a 30 mL syringe containing the local anaesthetic agent is attached, and 20 mL of lignocaine HCl is injected into the testis. The needle is then retracted, and the remaining 10 ml is injected subcutaneously; then the needle is withdrawn (see Fig. 21.3B). The process is repeated for the left testis. Remarkably, this is well tolerated in the vast majority of animals. The scrotal skin can now be aseptically prepared. It is mandatory to wait after this; at least 10 minutes is allowed to elapse so that the local anaesthetic will have its maximal effect. Before commencing surgery the level of sedation should be assessed, and a further incremental dose of sedation may be required to ensure that the colt remains adequately restrained for the entire procedure. The surgeon again grasps the left testis firmly against the scrotum, and a bold paramedian incision is made through the whole thickness of the scrotal wall (scrotal skin and vaginal parietal vaginal tunic) in a cranial to caudal direction, thus resulting in the ‘open’ castration technique. The incision is made large enough to allow the testis to be completely exposed. Gentle traction is then applied to the testis so that the ‘opened’ emasculators can be placed around the spermatic cord and testicular vessels with the cutting surface directly adjacent to the testis and the crushing surface positioned towards the direction of the spermatic vascular and not adjacent
• Fig. 21.1
Diagram of the anatomy of the reproductive organs of the stallion. (Redrawn with permission from Laing et al. 1988.)
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to the testis (the butterfly nut must be directed towards the testis (the so called ‘nut to nut’ orientation). The Serra emasculators are firmly closed at right angles to the spermatic cord, and the testis is removed. The emasculators must be closed completely, although this can require considerable force if the colt is large and the emasculators are not sharp. In these cases it may be best to first sever the caudal ligament of the epididymis with a scalpel, which allows the spermatic vessels and ductus deferens to be separated allowing the emasculators to be placed across the vessels and ductus separately (see Fig. 21.3 D). Once closed, the emasculators should be left in place for at least 5 minutes. During this time the procedure for removal of the left testis can commence. After removal of both testes, the scrotal incision is first inspected and if necessary manipulated to cover any protruding tissue; occasionally protruding connective tissue requires excision. Routine perioperative antibiotics are administered systemically, along with non-steroidal antiinflammatory drugs. Procaine penicillin should not be used in horses likely to compete within 6 weeks; this mainly applies to race horses. Fly control is mandatory in the summer months to repel the attention from flies and prevent myiasis and other forms of wound contamination; many practitioners prefer to perform routine castration in the spring and autumn. It is normal to advise that exercise is initially restricted for the first 36 hours postoperatively to only ‘walking in hand’, followed by a progressive return to exercise. Some trainers like to allow horses to swim shortly after castration, but although it may control swelling, this cannot be recommended due to the risk of wound contamination and even peritonitis.
Field Castration Closed castration can be undertaken in the field or in a cleaner environment (e.g., a hospital induction box), or the open and subsequently closed method can be used. These methods are usually performed under dissociative anaesthesia and are appropriate for colts of 6 months to 2 years irrespective of temperament. It may also be used in mature stallions in which there are financial constraints when an increased risk of herniation has been identified. The technique described here is that which is used routinely in the authors’ hospital because this appears to address the most significant complications and has been associated with very low complication rates.
B • Fig. 21.2
Ligaments of the scrotum. (A) Lateral view of the right spermatic sac of the horse. (B) Lateral aspect of the contents of the right spermatic sac of the horse. (Redrawn with permission from Cox 1982.)
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F E • Fig. 21.3
(A) Colt under sedation before standing castration. (B) The colt is adequately restrained, under sedation and standing, and local anaesthetic is injected into the scrotum. (C) The scrotal skin has been incised over the right testis. (D) The vaginal sac has been incised, and the surgeon has exteriorised the right testis and epididymis by gentle traction on both simultaneously. (E) The Serra emasculator has been applied to the spermatic cord of the right testis; note that the wing nut of the emasculator is adjacent to the testis. (F) The left testis and epididymis have been exteriorised by applying traction. Continued
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I H • Fig. 21.3, cont’d
(G) The Serra emasculator has been applied to the left spermatic cord. (H) The emasculator is closed without severing the spermatic cord and remains attached before the jaws are finally completely closed to severe the cord. (I) The scrotal incisions after completion of castration.
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B • Fig. 21.4
(A) The scrotal skin over the left testis has been incised, and with gentle pressure, the vaginal sac exposed. (B) The left testis is exteriorised.
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I • Fig. 21.4, cont’d
(C) The surgeon’s index finger is pointing to the epididymal ligament. (D) The epididymal ligament is being incised with a scalpel. (E) The epididymal ligament has been incised, and the testis and epididymis withdrawn from the vaginal sac. (F) The testis and epididymis are further exteriorised. (G) The Serra emasculator is applied to the spermatic cord (note that the wing nut is directed towards the testis). (H) The emasculator had been closed to severe the spermatic cord. (I) After excision of the testis and epididymis, the vaginal sac is closed by a continuous suture.
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Although premedication with acepromazine is slightly controversial due to the risk of priapism, the risk is outweighed because it helps to reduce anxiety and improves handling and anaesthetic induction. After this, the colt is then sedated with an α-2 adrenoceptor agonist (such as romifidine) with butorphanol. It is important to increase the dose if the animal is fractious because an adequate level of sedation is required before induction of anaesthesia. Before induction, palpation of the scrotum and inguinal region is performed to ensure that both testes are descended and that there is no scrotal hernia. Anaesthesia is normally induced with ketamine, and the horse is then positioned in dorsal recumbency. It is often helpful for an assistant to straddle the horse across its thorax while holding the forelimbs to balance the horse in dorsal decumbency. Lignocaine HCl (20 ml) is injected into each testis, and a further 10 ml is injected subcutaneously into the scrotal midline. The scrotum is aseptically prepared for surgery, and a fenestrated drape is placed. The surgeon kneels on the colt’s right side. The left testis is grasped with the left hand and pushed against the scrotum; the median raphae of the scrotum are readily identified as a distinct line. A skin incision parallel to the median raphe is made over the left testis, 1 to 5 cm from midline and of appropriate length, depending on the size of testicle. A second incision is then made in the vaginal tunic and the testis exteriorised. Traction is applied to the testis to tense the epididymal ligament, which is then sectioned with a scalpel. Forceps (Lane, Aliss, or Babcock) are applied to the vaginal tunic, and it is bluntly separated from the cord and spermatic vessel by traction. Serra emasculators are then applied to the vessels and ductus deferens and the testis removed. The emasculators are left in place for 3 to 4 minutes depending on the size of the colt. After removal of the emasculators, the spermatic vessels are inspected to ensure adequate haemostasis. A swab is then used to bluntly dissect the vaginal tunic from the associated scrotal connective tissue to the level of the external inguinal ring. The amount and texture of connective tissue varies considerably between breeds and types of horses, often being substantial in native ponies and cobs. The vaginal tunic is again grasped with forceps at the site of the incision and twisted to ablate the lumen down to the level of the external inguinal ring. The forceps are handed to an assistant to apply traction as the surgeon places a transfixing ligature of 5 M Polyglactin 910 through the vaginal tunic at the level of the external inguinal ring; this is hand tied on either side of the fixation. The emasculator is then applied to the vaginal tunic distal to the transfixing ligature, and it is removed; the emasculators should be left in position for 2 minutes to ensure adequate haemostasis of the cremaster muscle vasculature. The process is repeated on the right side, although it is quicker to remove both testes first, leaving emasculators attached on the right testis while closing the left vaginal tunic. After removal of both testes, the two parallel scrotal incisions are joined, and the median raphe of the scrotum is dissected out with scissors. This provides adequate drainage of the subcuticular dead space. The wound is inspected and the scrotum stretched to ensure that no connective tissue can prolapse through the incision; any tissue that may do so is removed. The horse is placed in lateral recumbency for recovery. As noted previously, this is the routine procedure used by the authors; however, in many circumstances, particularly when there is greater risk of wound contamination, the surgeon may elect to perform a closed castration whereby the vaginal tunic is not opened. Postoperative management is as for standing castration.
Theatre-Based Castration This technique, although the ideal procedure, is usually reserved for mature stallions due to cost. The aim of the surgery is to ensure a high level of sterility during the procedure and to close the skin incision after completion of the castration. There are some variations in technique depending on the preferences of the surgeon (Kummer et al. 2009); the authors recommend the following technique. Under routine general anaesthesia the urethra is catheterised, and the prepuce is temporarily closed with a continuous suture of 3 M nylon. The scrotum and inguinal region is aseptically prepared for surgery. A disposable impervious drape is applied, and an approximate V-shaped section of the drape is excised to expose the scrotum and the inguinal region while leaving the prepuce covered. An iodine impregnated adherent drape is then applied. A parainguinal incision is made midway between the external inguinal ring and the scrotum; care is taken to avoid large subcuticular vessels. The subcuticular fascia is incised, and then blunt dissection is used to expose the vaginal tunic. The tunic is grasped with Allis forceps, selecting a site where the cremaster muscle is not attached. The tunic is excised using a scalpel, and the incision extended with scissors to allow extraction of the testis by finger traction; the ligament of the epididymis is then transected. The ductus deferens and testicular vessels are ligated using a single 5 M polyglactin 910 suture. The spermatic cord and associated vessels are then severed with an emasculator distal to the ligature. A ‘graft passer’ is used to place a ligature around the vaginal tunic close to the external inguinal ring; this technique allows for minimal dissection, reduced chance of haemorrhage, and smaller dead space. The subcutaneous tissues are closed with 3 M polyglactin 910, and the skin with 2 M polyglactin 910 placed intradermally. The process is repeated on the contralateral testicle. After recovery from general anaesthesia, postoperative management for the horse is as described later in this chapter for standing castration, apart from the use of antibiotic medication which is not required because of the high level of asepsis. Laparoscopic Castration Routine castration can be undertaken laparoscopically in the standing horse by ligating and transecting the vasculature and ductus deferens intraabdominally. In most animals the testes will undergo avascular necrosis. However, in 3.4% of stallions, a testis does not become necrotic due to the establishment of an alternative blood supply from the cremaster muscle and/or the external pudendal artery (Voermans et al. 2006). Laparoscopic techniques have also been combined with open surgery (Rijkenhuizen & van der Harst 2017).
Complications Eventration The most common severe complication of equine castration is eventration, the protrusion of small intestine through the inguinal canal (so called ‘indirect herniation’). This can lead to trauma of the exposed bowel and is rapidly fatal. Eventration is prevented by techniques that either do not open the vaginal tunic or open it but after removal of the testis is subsequently close (as described previously). The risk period for herniation is within the first 36 hours of surgery. When eventration occurs, it is not possible to replace the herniated loop of small intestine into the abdomen. Therefore initial treatment requires protection of the exposed bowel and prevention of further herniation. If there is a relatively short
loop of small intestine involved, it can be treated as an essentially ‘first aid’ measure by just suturing the scrotum to contain it in order to facilitate transport of the affected individual to a surgical facility. If the loop of exposed bowel is substantial and/or it is damaged, immediate field-based general anaesthesia may be required to facilitate replacing the exposed intestine into the scrotum and retaining it by suturing the scrotal incision. Sometimes resection of the traumatised intestine is required, and the bowel clamps on the transected stumps are then sutured within the scrotum to enable transport for surgery. All cases will require general anaesthesia and a laparotomy to enable hernia reduction and facilitate resection and anastomosis of the affected bowel. The prognosis is good in peracute cases; however, in chronic cases, cardiovascular compromise and endotoxaemia will reduce the prognosis. Herniation of omentum is a much less serious complication, and generally the only indication is presence of the omentum protruding from the scrotal incision with no other clinical signs. Treatment involves applying gentle traction to expose a section of clean omentum, then simply excising the exposed tissue. If the amount of tissue is large, then ligation should be undertaken first; it is prudent to undertake a rectal examination to palpate the internal inguinal ring and thus ensure that no bowel appears to be entrapped. In simple cases the prognosis is good.
Haemorrhage Bleeding from the scrotum, cremaster muscle and subcuticular vessels is generally self-limiting and not significant, although it can be alarming to owners. Bleeding from the testicular vessels is potentially serious. This can be common particularly after standing castration, especially when ligation has not been performed. Many clinicians regard the presence of blood dripping from the scrotum for up to 24 hours after surgery as acceptable, but it can be avoided. Minimal but persistent bleeding is frustrating for the veterinarian because it may result in owners requesting often unnecessary repeat visits. Generally, this can be avoided by placing good quality emasculators correctly and leaving the emasculators in place for at least 5 minutes as described previously. If the bleeding is continuous rather than intermittent dripping or has persisted for over 24 hours, then ligation may be necessary. The cardiovascular status of the horse should be assessed clinically and a packed cell volume (PCV) value obtained before treatment. In cases with cardiovascular compromise or if the bleeding is minimal, the scrotum can be packed with gauze swabs in an attempt to apply pressure to the stumps of the cords; these can be sutured in place with heavy catgut. The gauze is removed 2 days later by breaking the catgut suture by a sudden pull on the gauze (Schumacher 2012). In cases in which there is severe haemorrhage without cardiovascular compromise or corrected haemorrhagic shock, short general anaesthesia may be required. The stump of the cord can be located and religated using a 5 M polyglactin 910 ligature and repeat emasculation. In addition, gauzes can be sutured in place with heavy catgut as described previously. Intraabdominal haemorrhage has been anecdotally reported postcastration; occasionally there is continued bleeding despite repeated attempts to ligate the stump. In such instances, standing laparoscopic ligation may be indicated (Trumble 2000). Using the author’s field anaesthesia technique (described previously), the vaginal tunic is ablated by twisting. The author has used this technique with concurrent laparoscopic visualisation of the internal inguinal ring; the spermatic cord stump does not retract into the
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abdomen. Because it is not present in the resected vaginal tunic, the stump must remain in the region of the external inguinal ring. In the authors’ experience, intraabdominal haemorrhage has not occurred using this technique.
Infection Bacterial infection most frequently results from contamination of the scrotal wound after surgery and therefore cannot be prevented at the time of surgery. Attempts should be made to reduce contamination, especially in the first 36 hours postoperative, when the animal is confined; the bedding must be clean, of adequate depth, and a faeces removed frequently. Straw or paper bedding is preferable to shavings, especially in young animals that are more likely to lie down; deep litter systems are not appropriate. After this period, increased exercise is important to reduce swelling and oedema and to promote drainage. In young animals, free paddock exercise is appropriate. Consideration of the timing of surgery is important as in summer months fly-borne contamination is difficult to prevent. In winter, very low temperatures can hamper scrotal healing. In older horses, controlled exercise may be more appropriate; hand walking, a treadmill, walker exercise, or leading are all suitable. A significant period of walking exercise is recommended: 45 minutes three times daily. Some trainers favour swimming during this period; although this is very effective at reducing swelling and oedema, it cannot be recommended due to the potential risk of an ascending infection through the inguinal canal and subsequent peritonitis. Scrotal Infection
In techniques without scrotal closure, subcutaneous scrotal infection is self-limiting because in most cases there is adequate drainage. Removal of the median raphe of the scrotum (as described previously) to create a single subcutaneous space further enhances drainage. If the scrotum is closed, contamination of the sutures may result in bacteria tracking into the subcutaneous dead space and the creation of a scrotal abscess. If scrotal drainage is inadequate in open scrotal techniques, the skin may heal and trap infection subcutaneously, again resulting in a scrotal abscess. Treatment primarily depends on establishing adequate drainage; with the horse adequately restrained, sutures must be removed and the scrotal incisions reopened. Local anaesthetic is injected into the abscess before reopening the incision, and this can almost always be achieved by blunt dissection, either digitally or using scissors. In extreme cases, general anaesthesia and surgical excision of the scrotum and removal of the median raphe may be appropriate. Exercise to reduce swelling and oedema is important; animals turned out may be inactive due to pain caused by the infection. Nonsteroidal antiinflammatory medication is important to reduce pain and swelling and facilitate exercise. Bacterial culture and sensitivity is appropriate but not always necessary. Broad spectrum antibiotics should be administered, although culture and sensitivity should be considered in serious cases in which longer course antimicrobial therapy may be necessary. Scirrhous Cord
Chronic micro pyogranulomatous infection of the stump of the spermatic cord is a more serious complication caused by bacterial infection. The source of infection is either contamination at surgery or, more commonly, secondary to scrotal infection. Techniques that do not close the vaginal tunic increase the risk of the development of a scirrhous cord secondary to scrotal infection. Horses with this condition will have a chronic purulent discharge from the scrotum.
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Palpation reveals a firm thickening of one or both of the spermatic cord stumps. Because the infection is pyogranulomatous with multiple microabscessation, antibiotic treatment alone is unsuccessful and inappropriate. Appropriate treatment is by surgical resection, performed under general anaesthesia. There is frequently substantial highly vascular fibrosis and adhesion formation around the stump, which needs to be dissected by both sharp and blunt techniques from the surrounding tissues. The spermatic stump is freed up to the level of the external inguinal ring and then transected with emasculators at the level of the external inguinal ring; in most cases, this is proximal to the thickened infected stump. However, on rare occasions the thickened stump continues into the inguinal ring, in which case laparoscopy may be indicated to facilitate transection of the stump proximal to the infection. Despite the potential risk of peritonitis, in the authors’ experience, this is extremely rare. The scrotum is left open for drainage. Appropriate antibiotics are administered based on culture and sensitivity, and the open scrotal wound is managed with appropriate exercise and frequent lavage. The prognosis with appropriate treatment is excellent; however, it is important to emphasise that even in cases in which there are financial constraints on the cost of treatment, surgery is necessary because attempts to treat with antibiotics alone will be unsuccessful and merely add to the cost. Peritonitis
Peritonitis is a rare but serious complication of equine castration. Animals presenting with any of the following signs postoperatively should be considered at risk: pyrexia, inappetence, colic, lethargy, and/or weight loss. Diagnosis is made after the analysis of peritoneal fluid obtained by abdominocentesis. Gross examination reveals a turbid and cloudy fluid. Laboratory investigations usually demonstrate an elevated total nucleated cell count and elevated protein concentration, and in a cytological examination, there are degenerate neutrophils and bacteria. The sample should be submitted for culture and sensitivity. Aggressive antimicrobial therapy, along with appropriate management of the scrotal wound/ scrotal abscess and/or scirrhous cord is required; in severe cases, peritoneal lavage may be necessary. The prognosis with appropriate management is good, although adhesion formation as a cause of colic after castration-induced peritonitis has been observed.
Postoperative Swelling and Oedema Swelling and oedema of the scrotum and prepuce are commonly seen over the first 5 days after castration but generally resolve by 2 weeks. An appropriate exercise regime should help to prevent the early closure of the surgical incision and thereby reduce swelling. Swelling that is severe or persists beyond this period should increase the suspicion of the presence of infection (see previous mention).
Cryptorchid Surgery in the Horse Aetiology Failure of one or both testes to descend into the scrotum is relatively common in the horse. The retained testis or testes may be present within the inguinal ring or in the abdomen. In some cases the gubernaculum and/or epididymis are present within the inguinal canal, although the testis/testes remain within the abdomen. Abdominal testes are most frequently located close to the internal inguinal ring but may be situated anywhere between the inguinal ring and the kidney.
It is noteworthy that anorchidism (congenital absence of the testes) and monorchidism (only a single testis present) are extremely rare, and so most cases seen in primary care practice will be either unilateral or bilateral cryptorchids.
Investigation of Cryptorchidism Careful palpation of the inguinal region under sedation may reveal the presence of an inguinal testis. Ultrasonography undertaken at the level of the inguinal ring enables an inguinal testis or an abdominal testis positioned close to the internal inguinal ring to be identified. Rectal palpation of the inguinal region may also be helpful. In horses of unknown history that exhibit stallion-like behaviour but in which no scrotal testes can be palpated, endocrine investigations are required to confirm the presence or absence of retained testes. This can be undertaken using an hCG stimulation test (in which elevated testosterone concentrations after administration is diagnostic) or measurement of basal oestrone sulphate (in which elevated concentrations are diagnostic). In these cases, careful visual examination of the scrotum for scarring from previous surgery may also be helpful.
Surgical Technique Cryptorchidectomy can be carried out by laparotomy, using an inguinal, parainguinal, suprapubic midline, or flank approach. Laparoscopic cryptorchidectomy is widely used in hospital practice; however, recent studies have found an increased complication rate compared with traditional techniques (Cribb et al. 2015).
Inguinal Exploration In cases in which an inguinal testis can be palpated or identified on ultrasound examination, surgical inguinal exploration is indicated. This can be done with the animal standing after administration of local anaesthetic into the scrotal and inguinal regions but is easier under general anaesthesia. After routine aseptic skin preparation, a scrotal incision is made parallel to the midline. Blunt finger dissection is used to expose the inguinal region. The gubernaculum and/or the epididymis and/ or the testis may be palpable. If not, then direct visualisation may reveal a white structure with a smoother, almost shiny, appearance compared with the local fatty connective tissue. This tissue is likely to be the gubernaculum and can be grasped with appropriate Lane, Babcock, or Allis forceps. Traction on the gubernaculum will often deliver the inguinal testicle into the surgical incision, and a routine castration can then be performed. Care should be taken to ensure that a testis is present because occasionally only the epididymis can be exteriorised because the testis is too large to pass through the internal inguinal ring and remains in the abdomen; rarely the epididymis is mistaken for a testis and is removed, thus leaving the testis in situ within the abdomen. Parainguinal Exploration If the testis is abdominal or inguinal, a parainguinal approach is preferred. In bilateral abdominal cryptorchids, both testes can usually be retrieved from a unilateral parainguinal incision. Rarely, bilateral parainguinal incisions may be required for bilateral abdominal cryptorchids; this is still preferred to a midline approach. A skin incision is made centred on the cranial boarder of the inguinal ring, 3 to 5 cm from the midline. Using blunt dissection, it is continued through the subcutaneous tissue to expose the
aponeurosis of the external abdominal oblique muscle, taking care to avoid damage to any blood vessels. This fibrous structure is incised with a scalpel, then the internal oblique and rectus muscle fibres are separated by blunt dissection between their fibres to produce a grid approach, which exposes the peritoneum. The peritoneum is then penetrated with a finger. The incision only needs to be large enough to allow access of two fingers. The first and index fingers are then placed through the incision and angled laterally towards the internal ring. The abdominal testis can frequently be grasped between the fingers and exteriorised by traction. If unsuccessful, the incision can be extended to allow the insertion of a hand and, if necessary, an arm into the abdomen. A systematic search of the abdomen is then undertaken starting at the internal inguinal ring to confirm the absence of any structure including a previously severed spermatic cord passing into the inguinal ring. The examination should then logically progress towards the bladder neck, along the bladder, and up to the kidney. Occasionally, an abdominal testis is situated caudal to the inguinal ring and is found within the pelvis. Familiarity with the feel of the tubular nature of the epididymis and more homogeneous and slightly firmer texture of the testis, compared with the abdominal viscera, is helpful. Rarely, the testis is not identified using this approach; one of the authors’ first surgical mentors then claimed ‘if all else fails opening the palm of the hand in the abdomen and thinking testis sometimes results in the offending structure being identified’. In bilateral cases, both testes can usually be removed from a single parainguinal incision; occasionally bilateral incisions are necessary when the spermatic cord is too short on the contralateral side. A midline approach is not recommended as the spermatic cord may be too short to enable the testis to be exteriorised. A parapenile midline approach can be used in bilateral cases but requires more dissection than the parainguinal approach. A direct approach through the inguinal ring is not recommended due to the increased risk of subsequent inguinal herniation. After emasculation and removal of the testis, the wound is closed with a single suture placed through both deep muscle layers to close the grid, followed by simple interrupted closure of the aponeurosis, using 5 M polyglycolic acid 910. The subcutaneous tissue is closed with 3.5 M polyglycolic acid 910, followed by 3 M polyglycolic acid 910 intradermal sutures.
Laparoscopic Exploration Ultrasonographic examination of the abdomen is very important before attempting laparoscopy because it often enables the identification of the approximate location of the testes and therefore assists with planning of the laparoscopic approach. Standing Laparoscopy
Standing laparoscopic cryptorchidectomy is a very elegant technique for the well-behaved and easily handled mature horses (Hendrickson & Wilson 1997). It is performed via two paralumbar portals, employing similar techniques to those used for ovariectomy (see later in this chapter). In bilateral cryptorchid cases the procedure can be repeated on the contralateral side. In unilateral cases, castration of the descended testis can be carried out at the same time, although ligation and transaction of the spermatic cord and vessels can still be done laparoscopically (Sassot et al. 2017). Laparoscopy Under General Anaesthesia
Laparoscopy under general anaesthesia may be appropriate for young and unhandled horses and ponies. An operating table capable of tilting into the Tredelenburg position is required. The laparoscope
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portal is placed cranial to the umbilicus; two instrument portals are placed either ipsilaterally or contralaterally in the caudal abdomen. After insufflation of the abdomen, the table is elevated into the Tredelenburg position so that the parts of the colon are displaced cranially to reveal the inguinal rings. Abdominal testes can be removed after transaction and ligation using a ‘ligasure’, via extension of the laparoscopic incision. Laparoscopy Complications
The most serious complication of the laparoscopic castration is penetration of viscera, when inserting the laparoscopic and instrument portals; this risk can be minimised as described for laparoscopic ovariectomy (see later in this chapter). In a recent review (Crib et al. 2015), it was found that horses undergoing laparoscopic cryptorchidectomy had increased surgical preparation times, increased surgery and anaesthesia times, and greater postoperative complications, compared with horses undergoing open cryptorchidectomy. Laparoscopy may be advantageous for a second attempt at cryptorchidectomy or if the testis location is unknown before surgery (Crib et al. 2015).
Castration (Ovariectomy of the Female (Mare) Horse Indications Routine ovariectomy of the mare is indicated to reduce unwanted ‘mare-like’ behaviour and prevent oestrus. It is likely that prevention of inappropriate aggressive and dominant behaviour is most effective if ovariectomy is carried out in young mares soon after the behaviour becomes apparent. However, the effects of ovariectomy on mare behaviour have not yet been fully investigated. Prepubertal ovariectomy of mares to prevent inappropriate behaviour is not currently undertaken, and its effectiveness has not been investigated. Ovariectomy is also indicated in cases of ovarian pathology, most commonly a granulosa cell tumour in which the mare may demonstrate a broad range of clinical signs, and there is commonly substantial enlargement of the ovary.
Historical Perspectives In the late 19th and early part of the 20th century, ovariectomy of mares was commonly performed in France and the UK; it was routine in the British military. The surgical technique employed was a transvaginal colpotomy, using chain ecraseurs to transect the ovarian pedicle and oviduct. Ironically, this was in some way an extremely modern technique, performed in the standing horse via a natural orifice approach. The practice fell out of favour as the horse became less essential for the armed forces. As the availability of hormonal methods of controlling ovarian activity increased and because simple suitable routine surgical methods were not applicable, there was a decline of routine mare ovariectomy by the mid to late 20th century. Nowadays, particularly in sports horse competitions, the gelding rather than the stallion or mare is preferred, as most riders regard the former as more predictable and trainable. Consequently, ovariectomy of fillies and mares appears to be becoming more popular (despite the legalisation of progesterone therapy to suppress oestrus for mares under FEI regulations). Recently, several minimally invasive laparoscopic techniques, either via a flank or vaginal approach, have been described. In the sport and leisure horse, the practice is gradually becoming more popular.
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However, evaluation of the benefits of mare ovariectomy and the most appropriate timing of the procedure need to be investigated so that mare owners can be advised correctly.
Surgical Technique Routine Ovariectomy A variety of techniques for ovariectomy are currently in use. The most common is a laparoscopic technique using three portals per side. The ovarian pedicle is sealed and transected using a ligature; the ovary is then removed by joining the two instrument portals using a blunt grid approach through the abdominal muscles. This results in the creation of a 20 cm long flank wound. Colpotomy techniques have also been reported; the challenge with using this technique is ensuring adequate sterility and closure of the vaginal incision. There have been other approaches advocated, including pararectal, hand-assisted laparoscopic, and trochar techniques. In the authors’ practice, a laparoscopic technique using a morcelator (Lund et al. 2014) is used. This involves two laparoscopic portals on each side of the animal. The ovarian pedicle is anaesthetised by the injection of lignocaine, and then the pedicle is sealed and transected using an electrosurgical ligating and cutting device, in a caudal to cranial direction, leaving the ovary suspended by the final 5 mm of cranial ovarian pedicle. The morcelater is then introduced through the instrument portal, and the ovary is removed. The two paired portals are closed with absorbable sutures in the muscle, and intradermal skin sutures. The mare can resume exercise 10 days later. It is likely that, with the continued development of safe elegant cost-effective techniques, routine ovariectomy of mares will once again become a commonly performed procedure in equine hospital practice. Removal of Granulosa Cell Tumours Granulosa cell tumours are benign ovarian tumours; they vary in size from little more than that of a normal ovary to over 50 cm in diameter in the most extreme cases. Removal by laparoscopic transection and ligation using an electrosurgical sealing and cutting device in the standing horse, as described previously, is now routine. Alternatively, laparoscopic stapling devices or ligatures can be used. Removal of the ovary can be undertaken in several ways. The technique used should be selected based on three factors: the size of the mare, the size of the ovary, and the depth of extra peritoneal fat. Granulosa cell tumours are multilocular and fluid filled; therefore the size of tumour can be significantly reduced by aspiration of the fluid. Relatively small tumours, especially in large lean mares, can be removed via a flank incision. The instrument portals are connected, and the skin incision is enlarged to an appropriate size for the ovary. The fascia and external oblique muscles are transected, and the incision is enlarged using a blunt finger grid dissection through the internal oblique and the transverse muscles; the peritoneum is also bluntly opened. The ovary is elevated into the incision by traction on the grasping forceps. With a portion of the tumour exposed, a stab incision is made into it, which enables a suction catheter to be introduced so that fluid can be aspirated to reduce the tumour size. Once flaccid, the mass can be exteriorised through the flank incision, and the wound is then closed. In all but the largest wounds, closure of the deeper layers is not necessary. The external oblique and fascia is closed using a simple continuous pattern with 5 M polyglycolic acid 910; the subcuticular layer is closed using a simple continuous pattern with
3 M polyglycolic acid 910, followed by intradermal sutures using 2 M polyglycolic acid 910. Alternative techniques for flank removal include intraabdominal needle aspiration and the use of endobags, with and without morcellation. For large or moderate sized tumours in small or obese horses and ponies, it is preferable to remove the mass in a second procedure under general anaesthesia. With the horse or pony in dorsal recumbency, a midline laparotomy incision is made, at least large enough for the insertion of the surgeon’s arm. A 50 × 50 cm disposable drape is placed into the abdomen. The ovary is placed onto the drape, and the drape carefully opened out. The four corners of the drape are then grasped by the surgeon and pulled out of the incision so that the ovary is pulled up into the incision. A stab incision is then made in the ovary to enable a suction catheter to be pushed into the mass to aspirate as much fluid as possible. When the mass is more flaccid, it is exteriorised through the incision by traction on the drape; the celiotomy incision can be extended if necessary. The wound is then closed routinely, and the horse recovered.
Complications Before the advent of laparoscopic techniques, the complication rate after open surgery was high. This is because the ovarian pedicle is relatively short and difficult to access, thus increasing the potential for inadequate ligation of the pedicle, leading to a high risk of potentially fatal haemorrhage. Traction on the ovary causes pain, which often necessitates increasing the depth of anaesthesia, and thus possible anaesthesia complications. Current laparoscopic techniques have resolved these issues. The pedicle is routinely anaesthetised by visually directly injecting local anaesthetic and then effectively ligated without the use of excessive tension. The main complication results from the risk of inadvertent visceral or splenic penetration when placing the first laparoscopic portal. This can be reduced by careful preoperative planning, including rectal palpation to assess the position of the colon, spleen, and caecum. The introduction of air into the abdomen via a Varres needle or teat cannula before the placement of the first trochar and cannula is also helpful. Guarded sharp trocars are also frequently used and are quite satisfactory. However, the threaded trocar further reduces the risk of visceral penetration as there is no forward stabbing force required for its insertion, and the peritoneum is incised in parallel plane. In most cases of inadvertent caecum or large colon penetration, the cannula remains in the viscera. This enables the surgeon to extend the incision so that the bowel and cannula can be carefully exposed and elevated by placing stay sutures either side of the penetration. The abdomen can then be packed-off with sterile saline–soaked, gauze swabs. The cannula can then be removed from the bowel, and the incision closed with a continuous double layer of inverting sutures, with 2 M polyglycolic acid 910 on a round body needle. If the bowel separates from the trocar, then significant faecal peritoneal contamination will occur, leading to rapidly fatal peritonitis. Conversion to a ventral midline laparotomy under general anaesthesia may be required to facilitate closure of the colon penetration followed by abdominal lavage. Large flank incisions are associated with higher morbidity rates due to seroma formation; they are also unsightly and may leave significant scarring. The complication rate is very low for an elective midline laparotomy. This technique should always be considered when the tumour is large, especially in small or fat animals, and when a good postoperative cosmetic result is important, such as in show animals.
References Cornwell JC, Hauer FP, Spillman TE, et al. J Anim Sci. 1973;36:215. Cribb NC, Koenig J, Sorge U. JAVMA. 2015;246:885. Klingel H. J Reprod Fertil Suppl. 1982;32:89. Kummer M, Gygax D, Jackson M, et al. Equine Vet J. 2009;41:547. Lund CM, Ragle CA, Lutter JD, Farnsworth KD. JAVMA. 2014;244: 1191. Rijkenhuizen ABM, van der Harst MR. Equine Vet J. 2017;49:776.
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Rosanowski SM, MacEoin F, Grahma RJTY, Riggs CM. Equine Vet J. 2018;50(3):327–332. Schumacher J. Testis. In: Auer JA, Stick JA, eds. Equine Surgery. 4th ed. St. Louis: Elsevier; 2012:821. Sassot LN, Ragle CA, Farnsworth KD, Lund CM. Can Vet J. 2017;58:1215. Shahin KA, Berg RT, Price MA. Reprod Nutr Dev. 1992;32:429. Trumble TN, Ingle-Fehre J, Hendrickson DA. JAVMA. 2000;15:1596. Voermans M, Rijkenhuizen AB, van der Velden MA. Equine Vet J. 2006;38:35.
Castration and Cryptorchid Surgery NEAL ASHTON
Castration of the Male Horse Indications for Castration Removal of the testes (also referred to as gelding, cutting, orchiectomy, orchidectomy) is routinely performed on male horses not intended for breeding purposes. The primary reason is to prevent stallion behaviour, which is generally regarded as inappropriate for most equestrian disciplines. In the wild, stallions organise into two distinct social groups: the harem bands that have one stallion and several mares, and the all male bachelor bands. Stallions can remain manageable if they remain in bachelor mode; however, interaction with other horses frequently results in harem band behaviour with increased aggression and reproductive drive (Klingel 1982). The average age that colts reach puberty is 69 weeks (range 55–101) (Cornwell et al. 1973). Stallions can be safely castrated at any age; however it is mostly undertaken at 6 months to 2 years of age. Some owners prefer to delay castration until after puberty to allow masculine features such as a crest or increased muscle mass to develop. In cattle, castration before puberty results in an increase in adult height due to delay in long bone growth plate closure (Shahin et al. 1992). It is possible that this also happens in the horse, but it is not documented or a reason for requesting castration by owners. Recently, there appears to have been an increasing tendency to castrate older animals once they have become unmanageable or once they have failed to perform to a level that justifies their use for breeding. The anatomy of the reproductive organs, in particular the penis of the stallion, is shown in Fig. 21.1 and a diagram of the testes Fig. 21.2.
Surgical Techniques Careful consideration of the age breed and type of horse, the premises at which the surgery is to be performed, and the methods for analgesia/anaesthesia should be made before selecting the surgical technique to be used. There are two broad surgical techniques, namely: (a) open castration (Fig. 21.3A–I) or (b) closed castration. An additional technique can be used in which an open castration is performed, and is subsequently closed; this prevents the possibility of postoperative herniation of abdominal viscera (Fig. 21.4 A–I). For an open castration, the vaginal tunics are incised, allowing direct visualisation of and access to the testicular vessels and the
ductus deferens, which may then be ligated and crushed or solely crushed with an emasculator; the tunics are left open after removal of the testes (see Figs 21.3 A–I). For a closed castration, the vaginal tunics are not incised, with haemostasis ensured by placing ligatures around the spermatic cord (or transfixing ligatures); in this way no opening is created into the peritoneal cavity. For the open and subsequently closed technique (see Figs 21.4 A–I), the following procedure is performed: after opening the tunic, the blood vessels and ductus deferens are ligated and transaction, and the vaginal tunic and skin are subsequently closed.
Standing Castration Standing castration (see Figs 21.3 A–I) can be undertaken in any colt that has normally descended testes, is large enough in height to enable the surgeon to access the scrotum by reaching underneath the abdomen, and has been well-handled with an amenable temperament. Owners should be warned about the risk of complications as they have been reported to occur in up to 60% of cases (Rosanowski et al. 2018). The technique is traditionally used in thoroughbred racehorses in the UK but is less popular in sports horses and warm bloods. There is anecdotal evidence that warm bloods are more prone to scrotal hernia, and this may be the reason for this difference. Standing castration is generally performed using the open technique using emasculators and without placing ligatures across the vessels and ductus deferens. The major disadvantage of this technique is the possible risk of uncontrolled haemorrhage occurring and that it does not prevent the risk of evisceration of abdominal contents through the inguinal canal because the vaginal tunic is left open. However, the internal and external inguinal rings are not in alignment in the standing horse, and so the risk appears to be less compared with when the procedure is performed in the recumbent anaesthetised animal, when herniation may occur as the animal rises to a standing position. The colt is first sedated, commonly using an α-2 adrenoceptor agonist (such as detomidine HCl) in combination with butorphanol tartrate; this results in profound sedation (Fig. 21.3A). The handler and surgeon remain on the left side of the colt, and the animal is made to stand against a wall on its right side. The surgeon approaches the scrotum from the horse’s shoulder to reduce the chance of being kicked if the colt/stallion suddenly and unexpected kicks out with his left hind leg. The right (furthermost) testis is grasped in the left hand so that it is pushed down firmly into the scrotum. An 18-gauge 40 mm needle is advanced in one swift 349
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movement perpendicular to the skin of the scrotum directly into the testis to the level of the needle hub. Once the needle is in position, a 30 mL syringe containing the local anaesthetic agent is attached, and 20 mL of lignocaine HCl is injected into the testis. The needle is then retracted, and the remaining 10 ml is injected subcutaneously; then the needle is withdrawn (see Fig. 21.3B). The process is repeated for the left testis. Remarkably, this is well tolerated in the vast majority of animals. The scrotal skin can now be aseptically prepared. It is mandatory to wait after this; at least 10 minutes is allowed to elapse so that the local anaesthetic will have its maximal effect. Before commencing surgery the level of sedation should be assessed, and a further incremental dose of sedation may be required to ensure that the colt remains adequately restrained for the entire procedure. The surgeon again grasps the left testis firmly against the scrotum, and a bold paramedian incision is made through the whole thickness of the scrotal wall (scrotal skin and vaginal parietal vaginal tunic) in a cranial to caudal direction, thus resulting in the ‘open’ castration technique. The incision is made large enough to allow the testis to be completely exposed. Gentle traction is then applied to the testis so that the ‘opened’ emasculators can be placed around the spermatic cord and testicular vessels with the cutting surface directly adjacent to the testis and the crushing surface positioned towards the direction of the spermatic vascular and not adjacent
• Fig. 21.1
Diagram of the anatomy of the reproductive organs of the stallion. (Redrawn with permission from Laing et al. 1988.)
A
to the testis (the butterfly nut must be directed towards the testis (the so called ‘nut to nut’ orientation). The Serra emasculators are firmly closed at right angles to the spermatic cord, and the testis is removed. The emasculators must be closed completely, although this can require considerable force if the colt is large and the emasculators are not sharp. In these cases it may be best to first sever the caudal ligament of the epididymis with a scalpel, which allows the spermatic vessels and ductus deferens to be separated allowing the emasculators to be placed across the vessels and ductus separately (see Fig. 21.3 D). Once closed, the emasculators should be left in place for at least 5 minutes. During this time the procedure for removal of the left testis can commence. After removal of both testes, the scrotal incision is first inspected and if necessary manipulated to cover any protruding tissue; occasionally protruding connective tissue requires excision. Routine perioperative antibiotics are administered systemically, along with non-steroidal antiinflammatory drugs. Procaine penicillin should not be used in horses likely to compete within 6 weeks; this mainly applies to race horses. Fly control is mandatory in the summer months to repel the attention from flies and prevent myiasis and other forms of wound contamination; many practitioners prefer to perform routine castration in the spring and autumn. It is normal to advise that exercise is initially restricted for the first 36 hours postoperatively to only ‘walking in hand’, followed by a progressive return to exercise. Some trainers like to allow horses to swim shortly after castration, but although it may control swelling, this cannot be recommended due to the risk of wound contamination and even peritonitis.
Field Castration Closed castration can be undertaken in the field or in a cleaner environment (e.g., a hospital induction box), or the open and subsequently closed method can be used. These methods are usually performed under dissociative anaesthesia and are appropriate for colts of 6 months to 2 years irrespective of temperament. It may also be used in mature stallions in which there are financial constraints when an increased risk of herniation has been identified. The technique described here is that which is used routinely in the authors’ hospital because this appears to address the most significant complications and has been associated with very low complication rates.
B • Fig. 21.2
Ligaments of the scrotum. (A) Lateral view of the right spermatic sac of the horse. (B) Lateral aspect of the contents of the right spermatic sac of the horse. (Redrawn with permission from Cox 1982.)
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B
C
D
F E • Fig. 21.3
(A) Colt under sedation before standing castration. (B) The colt is adequately restrained, under sedation and standing, and local anaesthetic is injected into the scrotum. (C) The scrotal skin has been incised over the right testis. (D) The vaginal sac has been incised, and the surgeon has exteriorised the right testis and epididymis by gentle traction on both simultaneously. (E) The Serra emasculator has been applied to the spermatic cord of the right testis; note that the wing nut of the emasculator is adjacent to the testis. (F) The left testis and epididymis have been exteriorised by applying traction. Continued
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I H • Fig. 21.3, cont’d
(G) The Serra emasculator has been applied to the left spermatic cord. (H) The emasculator is closed without severing the spermatic cord and remains attached before the jaws are finally completely closed to severe the cord. (I) The scrotal incisions after completion of castration.
A
B • Fig. 21.4
(A) The scrotal skin over the left testis has been incised, and with gentle pressure, the vaginal sac exposed. (B) The left testis is exteriorised.
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D
E
F
G
H
I • Fig. 21.4, cont’d
(C) The surgeon’s index finger is pointing to the epididymal ligament. (D) The epididymal ligament is being incised with a scalpel. (E) The epididymal ligament has been incised, and the testis and epididymis withdrawn from the vaginal sac. (F) The testis and epididymis are further exteriorised. (G) The Serra emasculator is applied to the spermatic cord (note that the wing nut is directed towards the testis). (H) The emasculator had been closed to severe the spermatic cord. (I) After excision of the testis and epididymis, the vaginal sac is closed by a continuous suture.
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Although premedication with acepromazine is slightly controversial due to the risk of priapism, the risk is outweighed because it helps to reduce anxiety and improves handling and anaesthetic induction. After this, the colt is then sedated with an α-2 adrenoceptor agonist (such as romifidine) with butorphanol. It is important to increase the dose if the animal is fractious because an adequate level of sedation is required before induction of anaesthesia. Before induction, palpation of the scrotum and inguinal region is performed to ensure that both testes are descended and that there is no scrotal hernia. Anaesthesia is normally induced with ketamine, and the horse is then positioned in dorsal recumbency. It is often helpful for an assistant to straddle the horse across its thorax while holding the forelimbs to balance the horse in dorsal decumbency. Lignocaine HCl (20 ml) is injected into each testis, and a further 10 ml is injected subcutaneously into the scrotal midline. The scrotum is aseptically prepared for surgery, and a fenestrated drape is placed. The surgeon kneels on the colt’s right side. The left testis is grasped with the left hand and pushed against the scrotum; the median raphae of the scrotum are readily identified as a distinct line. A skin incision parallel to the median raphe is made over the left testis, 1 to 5 cm from midline and of appropriate length, depending on the size of testicle. A second incision is then made in the vaginal tunic and the testis exteriorised. Traction is applied to the testis to tense the epididymal ligament, which is then sectioned with a scalpel. Forceps (Lane, Aliss, or Babcock) are applied to the vaginal tunic, and it is bluntly separated from the cord and spermatic vessel by traction. Serra emasculators are then applied to the vessels and ductus deferens and the testis removed. The emasculators are left in place for 3 to 4 minutes depending on the size of the colt. After removal of the emasculators, the spermatic vessels are inspected to ensure adequate haemostasis. A swab is then used to bluntly dissect the vaginal tunic from the associated scrotal connective tissue to the level of the external inguinal ring. The amount and texture of connective tissue varies considerably between breeds and types of horses, often being substantial in native ponies and cobs. The vaginal tunic is again grasped with forceps at the site of the incision and twisted to ablate the lumen down to the level of the external inguinal ring. The forceps are handed to an assistant to apply traction as the surgeon places a transfixing ligature of 5 M Polyglactin 910 through the vaginal tunic at the level of the external inguinal ring; this is hand tied on either side of the fixation. The emasculator is then applied to the vaginal tunic distal to the transfixing ligature, and it is removed; the emasculators should be left in position for 2 minutes to ensure adequate haemostasis of the cremaster muscle vasculature. The process is repeated on the right side, although it is quicker to remove both testes first, leaving emasculators attached on the right testis while closing the left vaginal tunic. After removal of both testes, the two parallel scrotal incisions are joined, and the median raphe of the scrotum is dissected out with scissors. This provides adequate drainage of the subcuticular dead space. The wound is inspected and the scrotum stretched to ensure that no connective tissue can prolapse through the incision; any tissue that may do so is removed. The horse is placed in lateral recumbency for recovery. As noted previously, this is the routine procedure used by the authors; however, in many circumstances, particularly when there is greater risk of wound contamination, the surgeon may elect to perform a closed castration whereby the vaginal tunic is not opened. Postoperative management is as for standing castration.
Theatre-Based Castration This technique, although the ideal procedure, is usually reserved for mature stallions due to cost. The aim of the surgery is to ensure a high level of sterility during the procedure and to close the skin incision after completion of the castration. There are some variations in technique depending on the preferences of the surgeon (Kummer et al. 2009); the authors recommend the following technique. Under routine general anaesthesia the urethra is catheterised, and the prepuce is temporarily closed with a continuous suture of 3 M nylon. The scrotum and inguinal region is aseptically prepared for surgery. A disposable impervious drape is applied, and an approximate V-shaped section of the drape is excised to expose the scrotum and the inguinal region while leaving the prepuce covered. An iodine impregnated adherent drape is then applied. A parainguinal incision is made midway between the external inguinal ring and the scrotum; care is taken to avoid large subcuticular vessels. The subcuticular fascia is incised, and then blunt dissection is used to expose the vaginal tunic. The tunic is grasped with Allis forceps, selecting a site where the cremaster muscle is not attached. The tunic is excised using a scalpel, and the incision extended with scissors to allow extraction of the testis by finger traction; the ligament of the epididymis is then transected. The ductus deferens and testicular vessels are ligated using a single 5 M polyglactin 910 suture. The spermatic cord and associated vessels are then severed with an emasculator distal to the ligature. A ‘graft passer’ is used to place a ligature around the vaginal tunic close to the external inguinal ring; this technique allows for minimal dissection, reduced chance of haemorrhage, and smaller dead space. The subcutaneous tissues are closed with 3 M polyglactin 910, and the skin with 2 M polyglactin 910 placed intradermally. The process is repeated on the contralateral testicle. After recovery from general anaesthesia, postoperative management for the horse is as described later in this chapter for standing castration, apart from the use of antibiotic medication which is not required because of the high level of asepsis. Laparoscopic Castration Routine castration can be undertaken laparoscopically in the standing horse by ligating and transecting the vasculature and ductus deferens intraabdominally. In most animals the testes will undergo avascular necrosis. However, in 3.4% of stallions, a testis does not become necrotic due to the establishment of an alternative blood supply from the cremaster muscle and/or the external pudendal artery (Voermans et al. 2006). Laparoscopic techniques have also been combined with open surgery (Rijkenhuizen & van der Harst 2017).
Complications Eventration The most common severe complication of equine castration is eventration, the protrusion of small intestine through the inguinal canal (so called ‘indirect herniation’). This can lead to trauma of the exposed bowel and is rapidly fatal. Eventration is prevented by techniques that either do not open the vaginal tunic or open it but after removal of the testis is subsequently close (as described previously). The risk period for herniation is within the first 36 hours of surgery. When eventration occurs, it is not possible to replace the herniated loop of small intestine into the abdomen. Therefore initial treatment requires protection of the exposed bowel and prevention of further herniation. If there is a relatively short
loop of small intestine involved, it can be treated as an essentially ‘first aid’ measure by just suturing the scrotum to contain it in order to facilitate transport of the affected individual to a surgical facility. If the loop of exposed bowel is substantial and/or it is damaged, immediate field-based general anaesthesia may be required to facilitate replacing the exposed intestine into the scrotum and retaining it by suturing the scrotal incision. Sometimes resection of the traumatised intestine is required, and the bowel clamps on the transected stumps are then sutured within the scrotum to enable transport for surgery. All cases will require general anaesthesia and a laparotomy to enable hernia reduction and facilitate resection and anastomosis of the affected bowel. The prognosis is good in peracute cases; however, in chronic cases, cardiovascular compromise and endotoxaemia will reduce the prognosis. Herniation of omentum is a much less serious complication, and generally the only indication is presence of the omentum protruding from the scrotal incision with no other clinical signs. Treatment involves applying gentle traction to expose a section of clean omentum, then simply excising the exposed tissue. If the amount of tissue is large, then ligation should be undertaken first; it is prudent to undertake a rectal examination to palpate the internal inguinal ring and thus ensure that no bowel appears to be entrapped. In simple cases the prognosis is good.
Haemorrhage Bleeding from the scrotum, cremaster muscle and subcuticular vessels is generally self-limiting and not significant, although it can be alarming to owners. Bleeding from the testicular vessels is potentially serious. This can be common particularly after standing castration, especially when ligation has not been performed. Many clinicians regard the presence of blood dripping from the scrotum for up to 24 hours after surgery as acceptable, but it can be avoided. Minimal but persistent bleeding is frustrating for the veterinarian because it may result in owners requesting often unnecessary repeat visits. Generally, this can be avoided by placing good quality emasculators correctly and leaving the emasculators in place for at least 5 minutes as described previously. If the bleeding is continuous rather than intermittent dripping or has persisted for over 24 hours, then ligation may be necessary. The cardiovascular status of the horse should be assessed clinically and a packed cell volume (PCV) value obtained before treatment. In cases with cardiovascular compromise or if the bleeding is minimal, the scrotum can be packed with gauze swabs in an attempt to apply pressure to the stumps of the cords; these can be sutured in place with heavy catgut. The gauze is removed 2 days later by breaking the catgut suture by a sudden pull on the gauze (Schumacher 2012). In cases in which there is severe haemorrhage without cardiovascular compromise or corrected haemorrhagic shock, short general anaesthesia may be required. The stump of the cord can be located and religated using a 5 M polyglactin 910 ligature and repeat emasculation. In addition, gauzes can be sutured in place with heavy catgut as described previously. Intraabdominal haemorrhage has been anecdotally reported postcastration; occasionally there is continued bleeding despite repeated attempts to ligate the stump. In such instances, standing laparoscopic ligation may be indicated (Trumble 2000). Using the author’s field anaesthesia technique (described previously), the vaginal tunic is ablated by twisting. The author has used this technique with concurrent laparoscopic visualisation of the internal inguinal ring; the spermatic cord stump does not retract into the
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abdomen. Because it is not present in the resected vaginal tunic, the stump must remain in the region of the external inguinal ring. In the authors’ experience, intraabdominal haemorrhage has not occurred using this technique.
Infection Bacterial infection most frequently results from contamination of the scrotal wound after surgery and therefore cannot be prevented at the time of surgery. Attempts should be made to reduce contamination, especially in the first 36 hours postoperative, when the animal is confined; the bedding must be clean, of adequate depth, and a faeces removed frequently. Straw or paper bedding is preferable to shavings, especially in young animals that are more likely to lie down; deep litter systems are not appropriate. After this period, increased exercise is important to reduce swelling and oedema and to promote drainage. In young animals, free paddock exercise is appropriate. Consideration of the timing of surgery is important as in summer months fly-borne contamination is difficult to prevent. In winter, very low temperatures can hamper scrotal healing. In older horses, controlled exercise may be more appropriate; hand walking, a treadmill, walker exercise, or leading are all suitable. A significant period of walking exercise is recommended: 45 minutes three times daily. Some trainers favour swimming during this period; although this is very effective at reducing swelling and oedema, it cannot be recommended due to the potential risk of an ascending infection through the inguinal canal and subsequent peritonitis. Scrotal Infection
In techniques without scrotal closure, subcutaneous scrotal infection is self-limiting because in most cases there is adequate drainage. Removal of the median raphe of the scrotum (as described previously) to create a single subcutaneous space further enhances drainage. If the scrotum is closed, contamination of the sutures may result in bacteria tracking into the subcutaneous dead space and the creation of a scrotal abscess. If scrotal drainage is inadequate in open scrotal techniques, the skin may heal and trap infection subcutaneously, again resulting in a scrotal abscess. Treatment primarily depends on establishing adequate drainage; with the horse adequately restrained, sutures must be removed and the scrotal incisions reopened. Local anaesthetic is injected into the abscess before reopening the incision, and this can almost always be achieved by blunt dissection, either digitally or using scissors. In extreme cases, general anaesthesia and surgical excision of the scrotum and removal of the median raphe may be appropriate. Exercise to reduce swelling and oedema is important; animals turned out may be inactive due to pain caused by the infection. Nonsteroidal antiinflammatory medication is important to reduce pain and swelling and facilitate exercise. Bacterial culture and sensitivity is appropriate but not always necessary. Broad spectrum antibiotics should be administered, although culture and sensitivity should be considered in serious cases in which longer course antimicrobial therapy may be necessary. Scirrhous Cord
Chronic micro pyogranulomatous infection of the stump of the spermatic cord is a more serious complication caused by bacterial infection. The source of infection is either contamination at surgery or, more commonly, secondary to scrotal infection. Techniques that do not close the vaginal tunic increase the risk of the development of a scirrhous cord secondary to scrotal infection. Horses with this condition will have a chronic purulent discharge from the scrotum.
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Palpation reveals a firm thickening of one or both of the spermatic cord stumps. Because the infection is pyogranulomatous with multiple microabscessation, antibiotic treatment alone is unsuccessful and inappropriate. Appropriate treatment is by surgical resection, performed under general anaesthesia. There is frequently substantial highly vascular fibrosis and adhesion formation around the stump, which needs to be dissected by both sharp and blunt techniques from the surrounding tissues. The spermatic stump is freed up to the level of the external inguinal ring and then transected with emasculators at the level of the external inguinal ring; in most cases, this is proximal to the thickened infected stump. However, on rare occasions the thickened stump continues into the inguinal ring, in which case laparoscopy may be indicated to facilitate transection of the stump proximal to the infection. Despite the potential risk of peritonitis, in the authors’ experience, this is extremely rare. The scrotum is left open for drainage. Appropriate antibiotics are administered based on culture and sensitivity, and the open scrotal wound is managed with appropriate exercise and frequent lavage. The prognosis with appropriate treatment is excellent; however, it is important to emphasise that even in cases in which there are financial constraints on the cost of treatment, surgery is necessary because attempts to treat with antibiotics alone will be unsuccessful and merely add to the cost. Peritonitis
Peritonitis is a rare but serious complication of equine castration. Animals presenting with any of the following signs postoperatively should be considered at risk: pyrexia, inappetence, colic, lethargy, and/or weight loss. Diagnosis is made after the analysis of peritoneal fluid obtained by abdominocentesis. Gross examination reveals a turbid and cloudy fluid. Laboratory investigations usually demonstrate an elevated total nucleated cell count and elevated protein concentration, and in a cytological examination, there are degenerate neutrophils and bacteria. The sample should be submitted for culture and sensitivity. Aggressive antimicrobial therapy, along with appropriate management of the scrotal wound/ scrotal abscess and/or scirrhous cord is required; in severe cases, peritoneal lavage may be necessary. The prognosis with appropriate management is good, although adhesion formation as a cause of colic after castration-induced peritonitis has been observed.
Postoperative Swelling and Oedema Swelling and oedema of the scrotum and prepuce are commonly seen over the first 5 days after castration but generally resolve by 2 weeks. An appropriate exercise regime should help to prevent the early closure of the surgical incision and thereby reduce swelling. Swelling that is severe or persists beyond this period should increase the suspicion of the presence of infection (see previous mention).
Cryptorchid Surgery in the Horse Aetiology Failure of one or both testes to descend into the scrotum is relatively common in the horse. The retained testis or testes may be present within the inguinal ring or in the abdomen. In some cases the gubernaculum and/or epididymis are present within the inguinal canal, although the testis/testes remain within the abdomen. Abdominal testes are most frequently located close to the internal inguinal ring but may be situated anywhere between the inguinal ring and the kidney.
It is noteworthy that anorchidism (congenital absence of the testes) and monorchidism (only a single testis present) are extremely rare, and so most cases seen in primary care practice will be either unilateral or bilateral cryptorchids.
Investigation of Cryptorchidism Careful palpation of the inguinal region under sedation may reveal the presence of an inguinal testis. Ultrasonography undertaken at the level of the inguinal ring enables an inguinal testis or an abdominal testis positioned close to the internal inguinal ring to be identified. Rectal palpation of the inguinal region may also be helpful. In horses of unknown history that exhibit stallion-like behaviour but in which no scrotal testes can be palpated, endocrine investigations are required to confirm the presence or absence of retained testes. This can be undertaken using an hCG stimulation test (in which elevated testosterone concentrations after administration is diagnostic) or measurement of basal oestrone sulphate (in which elevated concentrations are diagnostic). In these cases, careful visual examination of the scrotum for scarring from previous surgery may also be helpful.
Surgical Technique Cryptorchidectomy can be carried out by laparotomy, using an inguinal, parainguinal, suprapubic midline, or flank approach. Laparoscopic cryptorchidectomy is widely used in hospital practice; however, recent studies have found an increased complication rate compared with traditional techniques (Cribb et al. 2015).
Inguinal Exploration In cases in which an inguinal testis can be palpated or identified on ultrasound examination, surgical inguinal exploration is indicated. This can be done with the animal standing after administration of local anaesthetic into the scrotal and inguinal regions but is easier under general anaesthesia. After routine aseptic skin preparation, a scrotal incision is made parallel to the midline. Blunt finger dissection is used to expose the inguinal region. The gubernaculum and/or the epididymis and/ or the testis may be palpable. If not, then direct visualisation may reveal a white structure with a smoother, almost shiny, appearance compared with the local fatty connective tissue. This tissue is likely to be the gubernaculum and can be grasped with appropriate Lane, Babcock, or Allis forceps. Traction on the gubernaculum will often deliver the inguinal testicle into the surgical incision, and a routine castration can then be performed. Care should be taken to ensure that a testis is present because occasionally only the epididymis can be exteriorised because the testis is too large to pass through the internal inguinal ring and remains in the abdomen; rarely the epididymis is mistaken for a testis and is removed, thus leaving the testis in situ within the abdomen. Parainguinal Exploration If the testis is abdominal or inguinal, a parainguinal approach is preferred. In bilateral abdominal cryptorchids, both testes can usually be retrieved from a unilateral parainguinal incision. Rarely, bilateral parainguinal incisions may be required for bilateral abdominal cryptorchids; this is still preferred to a midline approach. A skin incision is made centred on the cranial boarder of the inguinal ring, 3 to 5 cm from the midline. Using blunt dissection, it is continued through the subcutaneous tissue to expose the
aponeurosis of the external abdominal oblique muscle, taking care to avoid damage to any blood vessels. This fibrous structure is incised with a scalpel, then the internal oblique and rectus muscle fibres are separated by blunt dissection between their fibres to produce a grid approach, which exposes the peritoneum. The peritoneum is then penetrated with a finger. The incision only needs to be large enough to allow access of two fingers. The first and index fingers are then placed through the incision and angled laterally towards the internal ring. The abdominal testis can frequently be grasped between the fingers and exteriorised by traction. If unsuccessful, the incision can be extended to allow the insertion of a hand and, if necessary, an arm into the abdomen. A systematic search of the abdomen is then undertaken starting at the internal inguinal ring to confirm the absence of any structure including a previously severed spermatic cord passing into the inguinal ring. The examination should then logically progress towards the bladder neck, along the bladder, and up to the kidney. Occasionally, an abdominal testis is situated caudal to the inguinal ring and is found within the pelvis. Familiarity with the feel of the tubular nature of the epididymis and more homogeneous and slightly firmer texture of the testis, compared with the abdominal viscera, is helpful. Rarely, the testis is not identified using this approach; one of the authors’ first surgical mentors then claimed ‘if all else fails opening the palm of the hand in the abdomen and thinking testis sometimes results in the offending structure being identified’. In bilateral cases, both testes can usually be removed from a single parainguinal incision; occasionally bilateral incisions are necessary when the spermatic cord is too short on the contralateral side. A midline approach is not recommended as the spermatic cord may be too short to enable the testis to be exteriorised. A parapenile midline approach can be used in bilateral cases but requires more dissection than the parainguinal approach. A direct approach through the inguinal ring is not recommended due to the increased risk of subsequent inguinal herniation. After emasculation and removal of the testis, the wound is closed with a single suture placed through both deep muscle layers to close the grid, followed by simple interrupted closure of the aponeurosis, using 5 M polyglycolic acid 910. The subcutaneous tissue is closed with 3.5 M polyglycolic acid 910, followed by 3 M polyglycolic acid 910 intradermal sutures.
Laparoscopic Exploration Ultrasonographic examination of the abdomen is very important before attempting laparoscopy because it often enables the identification of the approximate location of the testes and therefore assists with planning of the laparoscopic approach. Standing Laparoscopy
Standing laparoscopic cryptorchidectomy is a very elegant technique for the well-behaved and easily handled mature horses (Hendrickson & Wilson 1997). It is performed via two paralumbar portals, employing similar techniques to those used for ovariectomy (see later in this chapter). In bilateral cryptorchid cases the procedure can be repeated on the contralateral side. In unilateral cases, castration of the descended testis can be carried out at the same time, although ligation and transaction of the spermatic cord and vessels can still be done laparoscopically (Sassot et al. 2017). Laparoscopy Under General Anaesthesia
Laparoscopy under general anaesthesia may be appropriate for young and unhandled horses and ponies. An operating table capable of tilting into the Tredelenburg position is required. The laparoscope
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portal is placed cranial to the umbilicus; two instrument portals are placed either ipsilaterally or contralaterally in the caudal abdomen. After insufflation of the abdomen, the table is elevated into the Tredelenburg position so that the parts of the colon are displaced cranially to reveal the inguinal rings. Abdominal testes can be removed after transaction and ligation using a ‘ligasure’, via extension of the laparoscopic incision. Laparoscopy Complications
The most serious complication of the laparoscopic castration is penetration of viscera, when inserting the laparoscopic and instrument portals; this risk can be minimised as described for laparoscopic ovariectomy (see later in this chapter). In a recent review (Crib et al. 2015), it was found that horses undergoing laparoscopic cryptorchidectomy had increased surgical preparation times, increased surgery and anaesthesia times, and greater postoperative complications, compared with horses undergoing open cryptorchidectomy. Laparoscopy may be advantageous for a second attempt at cryptorchidectomy or if the testis location is unknown before surgery (Crib et al. 2015).
Castration (Ovariectomy of the Female (Mare) Horse Indications Routine ovariectomy of the mare is indicated to reduce unwanted ‘mare-like’ behaviour and prevent oestrus. It is likely that prevention of inappropriate aggressive and dominant behaviour is most effective if ovariectomy is carried out in young mares soon after the behaviour becomes apparent. However, the effects of ovariectomy on mare behaviour have not yet been fully investigated. Prepubertal ovariectomy of mares to prevent inappropriate behaviour is not currently undertaken, and its effectiveness has not been investigated. Ovariectomy is also indicated in cases of ovarian pathology, most commonly a granulosa cell tumour in which the mare may demonstrate a broad range of clinical signs, and there is commonly substantial enlargement of the ovary.
Historical Perspectives In the late 19th and early part of the 20th century, ovariectomy of mares was commonly performed in France and the UK; it was routine in the British military. The surgical technique employed was a transvaginal colpotomy, using chain ecraseurs to transect the ovarian pedicle and oviduct. Ironically, this was in some way an extremely modern technique, performed in the standing horse via a natural orifice approach. The practice fell out of favour as the horse became less essential for the armed forces. As the availability of hormonal methods of controlling ovarian activity increased and because simple suitable routine surgical methods were not applicable, there was a decline of routine mare ovariectomy by the mid to late 20th century. Nowadays, particularly in sports horse competitions, the gelding rather than the stallion or mare is preferred, as most riders regard the former as more predictable and trainable. Consequently, ovariectomy of fillies and mares appears to be becoming more popular (despite the legalisation of progesterone therapy to suppress oestrus for mares under FEI regulations). Recently, several minimally invasive laparoscopic techniques, either via a flank or vaginal approach, have been described. In the sport and leisure horse, the practice is gradually becoming more popular.
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However, evaluation of the benefits of mare ovariectomy and the most appropriate timing of the procedure need to be investigated so that mare owners can be advised correctly.
Surgical Technique Routine Ovariectomy A variety of techniques for ovariectomy are currently in use. The most common is a laparoscopic technique using three portals per side. The ovarian pedicle is sealed and transected using a ligature; the ovary is then removed by joining the two instrument portals using a blunt grid approach through the abdominal muscles. This results in the creation of a 20 cm long flank wound. Colpotomy techniques have also been reported; the challenge with using this technique is ensuring adequate sterility and closure of the vaginal incision. There have been other approaches advocated, including pararectal, hand-assisted laparoscopic, and trochar techniques. In the authors’ practice, a laparoscopic technique using a morcelator (Lund et al. 2014) is used. This involves two laparoscopic portals on each side of the animal. The ovarian pedicle is anaesthetised by the injection of lignocaine, and then the pedicle is sealed and transected using an electrosurgical ligating and cutting device, in a caudal to cranial direction, leaving the ovary suspended by the final 5 mm of cranial ovarian pedicle. The morcelater is then introduced through the instrument portal, and the ovary is removed. The two paired portals are closed with absorbable sutures in the muscle, and intradermal skin sutures. The mare can resume exercise 10 days later. It is likely that, with the continued development of safe elegant cost-effective techniques, routine ovariectomy of mares will once again become a commonly performed procedure in equine hospital practice. Removal of Granulosa Cell Tumours Granulosa cell tumours are benign ovarian tumours; they vary in size from little more than that of a normal ovary to over 50 cm in diameter in the most extreme cases. Removal by laparoscopic transection and ligation using an electrosurgical sealing and cutting device in the standing horse, as described previously, is now routine. Alternatively, laparoscopic stapling devices or ligatures can be used. Removal of the ovary can be undertaken in several ways. The technique used should be selected based on three factors: the size of the mare, the size of the ovary, and the depth of extra peritoneal fat. Granulosa cell tumours are multilocular and fluid filled; therefore the size of tumour can be significantly reduced by aspiration of the fluid. Relatively small tumours, especially in large lean mares, can be removed via a flank incision. The instrument portals are connected, and the skin incision is enlarged to an appropriate size for the ovary. The fascia and external oblique muscles are transected, and the incision is enlarged using a blunt finger grid dissection through the internal oblique and the transverse muscles; the peritoneum is also bluntly opened. The ovary is elevated into the incision by traction on the grasping forceps. With a portion of the tumour exposed, a stab incision is made into it, which enables a suction catheter to be introduced so that fluid can be aspirated to reduce the tumour size. Once flaccid, the mass can be exteriorised through the flank incision, and the wound is then closed. In all but the largest wounds, closure of the deeper layers is not necessary. The external oblique and fascia is closed using a simple continuous pattern with 5 M polyglycolic acid 910; the subcuticular layer is closed using a simple continuous pattern with
3 M polyglycolic acid 910, followed by intradermal sutures using 2 M polyglycolic acid 910. Alternative techniques for flank removal include intraabdominal needle aspiration and the use of endobags, with and without morcellation. For large or moderate sized tumours in small or obese horses and ponies, it is preferable to remove the mass in a second procedure under general anaesthesia. With the horse or pony in dorsal recumbency, a midline laparotomy incision is made, at least large enough for the insertion of the surgeon’s arm. A 50 × 50 cm disposable drape is placed into the abdomen. The ovary is placed onto the drape, and the drape carefully opened out. The four corners of the drape are then grasped by the surgeon and pulled out of the incision so that the ovary is pulled up into the incision. A stab incision is then made in the ovary to enable a suction catheter to be pushed into the mass to aspirate as much fluid as possible. When the mass is more flaccid, it is exteriorised through the incision by traction on the drape; the celiotomy incision can be extended if necessary. The wound is then closed routinely, and the horse recovered.
Complications Before the advent of laparoscopic techniques, the complication rate after open surgery was high. This is because the ovarian pedicle is relatively short and difficult to access, thus increasing the potential for inadequate ligation of the pedicle, leading to a high risk of potentially fatal haemorrhage. Traction on the ovary causes pain, which often necessitates increasing the depth of anaesthesia, and thus possible anaesthesia complications. Current laparoscopic techniques have resolved these issues. The pedicle is routinely anaesthetised by visually directly injecting local anaesthetic and then effectively ligated without the use of excessive tension. The main complication results from the risk of inadvertent visceral or splenic penetration when placing the first laparoscopic portal. This can be reduced by careful preoperative planning, including rectal palpation to assess the position of the colon, spleen, and caecum. The introduction of air into the abdomen via a Varres needle or teat cannula before the placement of the first trochar and cannula is also helpful. Guarded sharp trocars are also frequently used and are quite satisfactory. However, the threaded trocar further reduces the risk of visceral penetration as there is no forward stabbing force required for its insertion, and the peritoneum is incised in parallel plane. In most cases of inadvertent caecum or large colon penetration, the cannula remains in the viscera. This enables the surgeon to extend the incision so that the bowel and cannula can be carefully exposed and elevated by placing stay sutures either side of the penetration. The abdomen can then be packed-off with sterile saline–soaked, gauze swabs. The cannula can then be removed from the bowel, and the incision closed with a continuous double layer of inverting sutures, with 2 M polyglycolic acid 910 on a round body needle. If the bowel separates from the trocar, then significant faecal peritoneal contamination will occur, leading to rapidly fatal peritonitis. Conversion to a ventral midline laparotomy under general anaesthesia may be required to facilitate closure of the colon penetration followed by abdominal lavage. Large flank incisions are associated with higher morbidity rates due to seroma formation; they are also unsightly and may leave significant scarring. The complication rate is very low for an elective midline laparotomy. This technique should always be considered when the tumour is large, especially in small or fat animals, and when a good postoperative cosmetic result is important, such as in show animals.
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