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Abdominal ultrasonography as an adjunct to clinical examination in sheep
Accepted Manuscript Title: Abdominal ultrasonography as an adjunct to clinical examination in sheep Author: P. Scott PII: DOI: Reference:
S0921-4488(16)30364-9 http://dx.doi.org/doi:10.1016/j.smallrumres.2016.12.013 RUMIN 5371
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Small Ruminant Research
Please cite this article as: Scott, P., Abdominal ultrasonography as an adjunct to clinical examination in sheep.Small Ruminant Research http://dx.doi.org/10.1016/j.smallrumres.2016.12.013 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Abdominal ultrasonography as an adjunct to clinical examination in sheep
P. Scott*
Division of Veterinary Clinical Sciences, R(D)SVS, University of Edinburgh, Easter Bush, Roslin, Midlothian, Scotland, EH25 9RG, United Kingdom. *
Corresponding author: [email protected]
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ABSTRACT Modern portable ultrasound machines provide the veterinary clinician with an inexpensive and non-invasive method to further examine sheep on farm, which would take no more than 2-5 minutes with results available immediately. Trans-abdominal ultrasonographic examination provides veterinarians with valuable information regarding bladder distension and uroperitoneum caused by obstructive urolithiasis, which greatly facilitates prompt corrective surgery. Advanced hydronephrosis, which affords a grave prognosis for urolithiasis cases, is readily identified by an increased renal pelvis and thinned cortex. Unless caused by large numbers of migrating immature liver flukes, accumulation of inflammatory exudate in the peritoneal cavity is uncommon in sheep. Unlike cattle, infection arising from the gastrointestinal tract, e.g., traumatic reticuloperitonitis, is rare in sheep. Renal, intestinal, kidney and bladder tumours can be identified during ultrasonographic examination, but these conditions affect individual sheep and are not a significant flock problem.
Keywords: abdomen, fasciolosis, hydronephrosis, sheep, ultrasonography, urolithiasis..
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1. Introduction Urethral obstruction occurs occasionally in mature rams with most calculi lodging within the vermiform appendix (Kümper, 1994; Scott, 2000); obstruction proximal to the sigmoid flexure is less common. Early recognition of clinical signs of dysuria and stranguria by the farmer and prompt veterinary treatment are essential to ensure a satisfactory outcome, because irreversible hydronephrosis quickly results from urinary back pressure (Kümper, 1994; Biricik et al., 2003). Early diagnosis has allowed surgical correction of breeding rams by tube cystotomy (Cockcroft, 1993) and rapid implementation of control measures (Angus, 2000) to prevent further cases. While rupture of the urethra can occur in urolithiasis cases with subcutaneous accumulation of urine along the ventral abdominal wall, rupture of the bladder is rare (Scott, 2000; Scott, 2007), except for neglected cases (Kümper, 1994). Marked urinary bladder distension, hydronephrosis and perirenal fluid accumulation were identified ultrasonographically in two rams from the same farm. Both rams were observed to urinate, but flow rate of urine was estimated to be smaller than normal and duration of urination was reduced to around 5to 10 seconds, when around 20 to 30 seconds is considered normal. There was normal tail and rectal tone and normal perineal and pelvic limb reflexes. A presumptive diagnosis of pelvic nerve dysfunction causing detrusor atony and bladder distension with secondary pressure-induced hydronephrosis had been suggested, but could not be proved; detailed dissection at post-mortem examination found no evidence of urethral obstruction (Scott, 2012). This diagnosis had become only possible after combining clinical and ultrasonographic findings; post-mortem examination would most likely have yielded a diagnosis of obstructive urolithiasis. Urinary tract infections leading to pyelonephritis are rare in sheep, with the exception of the cases of male animals, which have undergone subischial urethrostomy surgery to bypass the site of obstructive urolithiasis. Biricik et al. (2003) have concluded from their studies on young lambs with obstructive urolithiaisis that B-mode and colour-coded Doppler sonography might provide useful information for detection of changes in kidneys, e.g., hydronephrosis or renal swelling, as well as elevated resistance in the renal interlobar artery. While hepatocellular tumours are not uncommon in old sheep, such lesions are usually only recognised at the slaughter plant in ewes culled for poor condition; however, Lofstedt et al. (1988) have reported that liver tissue obtained via ultrasound-guided percutaneous liver biopsy had suggested a diagnosis of adenocarcinoma of the liver, later confirmed at post-mortem examination. Large liver abscesses caused by Corynebacterium pseudotuberculosis, the causal agent of caseous lymphadenitis, are not uncommon in many countries, including the USA (Stoops et al., 1984; Gnad et al., 2000). In cases with large liver abscesses, these can be readily identified during ultrasonographic examination (Scott et al., 1997a). 3
Ultrasonographic examination of the liver has confirmed the presence of hydatid cysts therein and its potential use as a mass screening approach for cystic echinococcosis (Lahmara et al., 2007); a similar conclusion was reported by Guarnera et al. (2001). Cysts of Echinococcus granulosus in the liver of sheep were localised by ultrasonographic examination and injected with dipeptide methyl ester and the treatment response monitored by imaging (Lahmara et al., 2006). Hepatomegaly and the demonstration of multiple hyperechoic dots within the hepatic parenchyma, representing accumulations of inflammatory cells, have been reported in sheep with subacute fasciolosis (Scott et al., 2004) and these lesions resolved within one month of treatment with triclabendazole. Romanski (2004) reported gall bladder dimensions measured ultrasonographically in sheep after various intervals during fasting with a doubling of volume after two days and suggested that such measurement could provide important clinical information. These data support the post-mortem findings of gall bladder distension in cachectic sheep. While ultrasound-guided aspiration of bile from the gall bladder has been recommended for detection of fluke eggs in cattle (Braun et al., 1996), such examinations are not necessary to establish a diagnosis of patent fascioliasis in sheep, because the coproantigen ELISA test permits much earlier recognition by identifying immature fluke infestation. Perinatal lamb mortality, defined as losses within the first three days of life, is the major cause of lamb deaths with estimates ranging from 10 to 25 per cent (Whitelaw, 1976; Eales et al., 1982; Barlow et al., 1987; Hindson and Winter, 1990). Ultrasonographic examination of the abomasum of neonatal lambs provides an immediate indication to the veterinary investigator whether lambs have sucked. The difference in lamb abomasal diametre before and after sucking is so large, 3 versus 8 to 10 cm, that minor errors in individual lamb recordings would not affect the collection of meaningful data from 20 or more lambs and their interpretation (Scott et al., 1997b).
2. Methodology for ultrasonographic examination 2.1. Bladder and ventral abdomen
The absence of fleece in the inguinal area expedites site preparation, when examining the ventral and caudal abdomen in sheep. Ultrasonographic examination of the bladder and the caudal abdomen are undertaken in the standing animal, using either 5.0 MHz linear array or (micro-convex) sector scanners. The caudal abdomen is examined for the bladder and gravid uterus and increased peritoneal fluid. The right inguinal region immediately cranial to the pubis is cleaned using a mild detergent solution diluted in warm tap water to remove superficial grease and debris. The right inguinal region is chosen, because the left side of the abdomen is largely occupied by the rumen. Ultrasound gel is applied to the probe head. The transducer head is directed toward the animal’s tail head to image the bladder. When the bladder is enlarged, an estimate of its size can be obtained by moving a 5.0 MHz linear scanner (field 4
depth of 10.0 cm) cranially along the ventral midline from the level of the pubic symphysis, because of its cylindrical rather than spherical shape when distended.
2.2. Right kidney
Examination of the right kidney necessitates shaving the fleece from the right sublumbar fossa immediately caudal to the last rib. The sector transducer head is firmly held against the skin to ensure good visualisation of the right kidney juxtaposed the caudal lobe of the liver. Advanced hydronephrosis can be identified by the grossly increased renal pelvis, which is represented by the anechoic (fluid-filled) centre of the kidney. It is not always possible to scan the left kidney in sheep via the flank; however, such examination is not necessary, as the urinary tract obstruction is distal to the ureters, therefore the disorder affects both kidneys equally.
2.3. Liver
The liver can be imaged from the seventh to eleventh intercostal spaces halfway down the right chest wall, and sometimes immediately caudal to the costal arch at this level with the 5.0-6.5 MHz sector probe head pointed towards the contralateral shoulder (Scott et al., 2005). Hepatocellular tumours are not uncommon in old sheep. Such lesions are usually only recognised at the slaughter plant in ewes culled for poor condition
2.4. Abomasal diametre of neonatal lambs
The abomasal diametre of neonatal lambs can be measured using a 5.0 MHz sector scanner applied at right angles to the abdominal wall at the umbilicus. The abomasum can be clearly identified as a hypoechoic area delineated by a hyperechoic wall. The vertical distance is measured between the probe head and the far abomasal wall.
3. Ultrasonographic findings 3.1. Ascites
There is scant peritoneal fluid in normal sheep, which may not be visualised during ultrasonographic examination. Ascitic fluid appears as an anechoic area with abdominal viscera displaced dorsally in the standing animal. The intestines are clearly outlined as hyperechoic (bright white) lines/circles containing material of varying echogenicity (Fig. 1; Suppl. material 1). By 5
maintaining the probe head in the same position, digesta can be visualised as multiple small dots of varying echogenicity forcibly propelled within the intestines.
3.2. Peritonitis
With the exception of subacute fasciolosis (Figs 2, 3), significant peritoneal effusion/exudation is rarely seen in sheep with the reaction limited by the omentum to focal fibrinous/fibrous adhesions and localised accumulations of peritoneal exudate. The most common exception is intestinal adenocarcinoma, where transcoelomic spread of the tumour causes impaired lymphatic drainage and accumulation of transudate (Figs 4, 5). A large accumulation of transudate is also common in some cases of bacterial endocarditis (Figs 6, 7). Abscesses within the peritoneal cavity are rapidly enveloped by the omentum (Fig. 8). The peritoneal abscess appears as a circular anechoic area containing multiple hypechoic dots surrounded by an anechoic capsule (Fig. 8; Suppl. material 2); the contents are static, which differentiates this structure from a cross section of intestine.
3.3. Urinary tract
The urinary bladder is not usually imaged during trans-abdominal ultrasonographic examination in normal sheep, because it is contained within the pelvic canal. When distended with urine, the bladder extends 6 to 10 cm in diametre cranial to the pelvic brim in 20 to 50 kg growing lambs (Fig. 9; Suppl. material 3, 4) and 12 to 20 cm in diametre in mature rams (Fig. 10). The bladder wall appears as a hyperechoic circle; oedema of the wall results in widening of this white line. Rupture of the bladder does not occur (Figs 11, 12), except for neglected cases and even then urine leaks across the taut bladder wall rather than true rupture (Suppl. material 5, 6). In such cases, the distended bladder can be imaged within the uroperitoneum (Figs 13, 14). Fibrin tags can sometimes be visualised within the uroperitoneum as fine hyperechoic filaments within the anechoic fluid. Significant hydronephrosis develops after high urinary backpressure of 5 to 7 days’ duration, therefore ultrasonographic examination of the right kidney should be undertaken at the same time (Suppl. material 7). This period is based on the author’s ultrasonographic and post-mortem findings, often at the time of presentation, and therefore relies upon an accurate assessment of the duration of illness reported by the owner, which may be an underestimation in many cases. High urinary backpressure leads to hydroureters and hydronephrosis (Fig. 15). The sector transducer head is firmly held against the skin to ensure good visualisation of the right kidney juxtaposed the caudal lobe of the liver (Fig. 16; Suppl. material 8, 9). Early stages of disorders (Fig. 17; Suppl. material 10, 11) may be difficult to interpret with respect to prognosis, but it is useful to ascertain that there is no advanced hydronephrosis. Advanced hydronephrosis can be readily 6
identified by the grossly increased renal pelvis, which is represented by the anechoic (fluid-filled) centre of the kidney (Figs 17-20; Suppl. material 12). Haemorrhage surrounding the kidney has resulted in displacement of the right kidney from the abdominal wall (Figs 21-24; Suppl. material 13). Clot formation results in broad hyperechoic strands within the anechoic serum. Fluid accumulation surrounding the kidney appears as an anechoic layer extending to 2 to 3 cm (Fig. 25), where there is obvious hydronephrosis confirmed at post-mortem examination (Fig. 26; Suppl. material 14). Presence of hydronephrosis due to high urinary backpressure would suggest that this fluid would likely be urine, but this cannot be determined from the sonogram alone. Leakage of urine surrounding the kidney(s) may not cause obvious clinical signs (Fig. 27) and trans-abdominal ultrasonographic examination may reveal surprising pathology (Fig. 28-33), whereby there is 12-13 cm of fluid separating the right kidney from the abdominal wall (Fig. 28) containing fibrin strands. There is obvious hydronephrosis (Fig. 29) with these sonographic findings confirmed at postmortem examination (Figs 30-33). There is marked distension of both ureters (hydroureters) and distension of the bladder (Fig. 32), which has not ruptured nor is there uroperitoneum; no reason was found to explain why fluid (urine) was present surrounding only the right kidney. The findings reported here and featured in Fig. 21-33 indicate that ultrasonographic examination of the right kidney must be undertaken before attempted surgical correction of urolithiasis. Ultrasonographic monitoring of the indwelling Foley catheter can be undertaken following tube cystotomy (Fig. 34; Suppl. material 15)
3.4. Cystitis
In cystitis, the bladder wall appears thicker than normal with fibrin tags on the mucosal surface, which appear as hyperechoic strands. Large fibrin clots, typically represented by irregularly shaped 2 to 4 cm diametre hypoechoic circles containing hyperechoic dots, may be present within the distended bladder (Fig. 35).
3.5. Leiomyoma
Leiomyomas are not commonly observed in sheep and would appear as a large (>14 cm) uniformly hypoechoic mass dorsal to the bladder (Figs 36, 37).
3.6. Renal tumour
Renal tumours have been rarely reported in sheep. Development of a renal tumour over three months is shown sequentially (Figs 38-40; Suppl. material 16), during which time the tumour increased 7
in size from 8 cm to 16 cm in diametre. Intra-abdominal haemorrhage was identified after two months, which became extensive one month later, when the ewe was euthanised for welfare reasons (Figs 4146; Suppl. material 16). It is important to recognise that the ewe was clinically normal throughout this period and had a normal appetite and its welfare was not compromised; indeed, body condition increased from a score of 1.0 at admission (scale 1-5; Fig. 46) to 3.0 at the time of euthanasia (Fig. 47); a large amount of omental fat was evident at post-mortem examination (Suppl. material 16). The provisional diagnosis was pyelonephritis (urinalysis revealed the presence of blood, protein and white cells) and the sheep was treated with procaine penicillin daily for three weeks. Diagnosis could not be made on clinical examination alone, hence the ultraonographic findings can be used by veterinarians when presented with similar images.
3.7. Liver
Unlike cattle, liver abscesses have not been identified in sheep by this author. Furthermore, examination of the liver in ewes with pregnancy toxaemia has failed to identify consistent sonographic changes. Gall bladder distension (Suppl. material 17) and nodular hyperplasia (Suppl. material 18) have been identified in individual ewes with chronic fasciolosis.
3.8. Miscellaneous conditions
3.8.1. Intra-abdominal haemorrhage Haemorrhage into the broad ligament can occur in cases of vaginal prolapse (Figs 48, 49).
3.8.2. Diaphragmatic hernia Diaphragmatic hernia has been observed in three ewes with no history of severe trauma. Examination of the normal side of the chest (Suppl. material 19) revealed that the heart pressed against the chest wall; the presence of intestines in the contralateral chest cavity confirms the diaphragmatic hernia (Suppl. material 20).
4. Discussion Many farm animal practitioners use 5.0 MHz linear array scanners for early pregnancy diagnosis in cattle, but this equipment may also be used to examine abdominal viscera in sheep, albeit the depth of field is limited to 10 cm. Examination using the 5.0 MHz linear array scanner may underestimate the size of the distended bladder, but this does not affect the diagnosis, nor the immediate action of the veterinary surgeon to examine the ram’s vermiform appendage for obstruction. A 5.0 MHz sector (microconvex) scanner is necessary to image the right kidney for hydronephrosis. 8
Recording of ultrasonographic findings on to a laptop or other suitable mobile storage device is strongly recommended, because it allows the veterinarian to accurately monitor changes over time, including response to treatments, and to retrospectively analyse sonographic findings should the animal be examined post-mortem, due to advanced disease or another reason, e.g., animal welfare concerns. Increasingly, digital information, e.g., images or video recordings of problem cases, can be e-mailed to experts for immediate interpretation. Such dialogue and dissemination of field data benefits both parties. Publication of such findings should be more actively encouraged. Post-mortem examination findings have been included in figures and in the video recordings in this article to aid interpretation of the sonograms.
4.1. Ascites
Large accumulations of peritoneal fluid are uncommon in sheep, even in those animals with profound hypoalbuminaemia caused by either paratuberculosis or severe parasitism, e.g., haemonchosis or chronic fasciolosis. Unlike cattle, ascites secondary to right-sided heart failure is rare in sheep, but has been reported secondary to bacterial endocarditis (Scott and Sargison, 2001). A large accumulation of peritoneal fluid in older sheep is often caused by impaired lymphatic drainage subsequent to transcoelomic spread of intestinal adeoncarcinoma (Scott, 2007). Accumulation of peritoneal exudate and/or peritonitis arising from lesions in the gastrointestinal tract, e.g., traumatic reticulitis or abomasal ulceration/perforation is uncommon in sheep. Whilst uterine tears can give rise to extensive accumulation of peritoneal exudate in cattle, such pathology is rare in sheep and may be related to the more extensive tears suffered by sheep leading to rapid death.
4.2. Bladder and kidney
While marked elevations of blood urea nitrogen and creatinine concentrations occur as a result of partial or complete urethral obstruction, such increases are not pathognomonic and there are no recognised threshold concentrations above which urolithiasis can be confirmed. Examination using a 5.0 MHz linear array scanner readily identifies distended bladder and uroperitoneum if present, but the true size of the bladder may not be measured, because it may extend to 20 cm in diametre, thereby exceeding the 10 cm field of many linear array scanners. It must be remembered that the bladder in normal male sheep is largely contained within the bony pelvis, therefore presence of the bladder extending for up to 10 cm or more over the pelvic brim is abnormal, determination of the actual size of the bladder is of secondary importance (Scott, 2000). High urinary back pressure results in marked hydronephrosis in approximately 5 to 7 days with an associated grave prognosis, but there are insufficient published data on renal measurements to decide whether a tube cystotomy should be undertaken. Interpretation of gross findings at post-mortem 9
examination has suggested that the rams featured in Figs 17-19 would have been highly unlikely to recover should surgery had been performed. Marked urinary bladder distension, hydronephrosis and perirenal fluid accumulation were identified ultrasonographically in two rams without obvious urethral obstruction leading to a presumptive diagnosis of pelvic nerve dysfunction causing detrusor atony and bladder distension with secondary pressure-induced hydronephrosis (Scott, 2012). This diagnosis was only possible after combining clinical and ultrasonographic findings; post-mortem examination would most likely have yielded a diagnosis of obstructive urolithiasis.
4.3. Liver
Ultrasonographic examination of the liver has limited application in small ruminant practice. Fatty infiltration of the liver cannot be reliably detected and preventive measures for ovine pregnancy toxaemia are best implemented by assessment of ewes’ nutritional regime 5 to 6 weeks before the anticipated lambing date (Russel, 1985), coupled with measurements of β-hydroxybutyrate blood concentrations in pregnant animals in the flocks. Whilst there are characteristic sonographic changes in the liver caused by developing liver flukes, control measures are much more important, which are based upon perceived risk following analysis of meteorological data over the summer months. Routine preventive flukicide treatments are practiced by sheep farmers in endemic fluke areas, where treatment efficacy can be assessed by measuring faecal coproantigen ELISA concentrations, especially where triclabendazole resistance is suspected.
4.4. Vaginal prolapse
Complications to vaginal prolapse may include haemorrhage into the broad ligament. This can be detected by transabdominal ultrasonographic examination and may require an emergency caesarean operation to correct such problems, but there are no such reports in the literature.
5. Concluding remarks In summary, trans-abdominal ultrasonographic examination is most usefully employed to support a provisional clinical diagnosis of urolithiasis and to investigate whether there is significant hydronephrosis ahead of tube cystotomy surgery. Other complications, e.g., perirenal haemorrhage and accumulation(s) of exudate, can also be detected sonographically. The high financial value of stud rams allows such further examination, which is rarely afforded for other conditions in commercial-value sheep. The examination costs only the veterinary practitioner’s time, but can often provide immediate clinical information allowing either prompt treatment/surgery or euthanasia for welfare reasons due to 10
a hopeless prognosis. The greater availability of excellent quality ultrasound probes at relatively low cost allows exciting diagnostic possibilities for all small ruminant practitioners.
Conflict of interest statement The author of this paper has no financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper.
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References Angus KW, 2000. Diseases of the urinary tract, in Martin WB, Aitken ID (eds): Diseases of sheep. Blackwell Science, Oxford, UK, pp 344-351. Barlow, R.M., Gardiner, A.C., Angus, K.W., Gilmour, J.S., Mellor, D.J., Cuthbertson, J.C., Newlands, G., Thompson, R., 1987. Clinical, biochemical and pathological study of perinatal lambs in a commercial flock. Vet Rec 120: 357, 1987. Biricik, H.S., Çimtay, I., Öztürk, A., Aksoy, G., 2003. B-Mode and colour coded doppler sonography of kidneys in lambs with urolithiasis and in healthy lambs. Deutsche Tierarztliche Wochenschrift 110. 502-505. Braun, U., Pusterla, N., Wild, K., 1996. Ultrasonographic examination of the liver and gallbladder in cows: Abnormal findings. Compendium on Continuing Education for the Practicing Veterinarian 18, 1255-1269. Cockcroft, P.D., 1993. Dissolution of obstructive urethral urolithiasis in a ram. Vet Rec 132, 486-487. Eales, F.A., Gilmour, J.S., Barlow, R.M., Small, J., 1982. Causes of hypothermia in 89 lambs. Vet Rec 110, 118120. Gnad, D.P., Van Metre, D.C., Angelos, S.M., Spaeth, C., 2000. Diagnosing weight loss in sheep: A practical approach. Compend Contin Educ Pract Vet 22, S16-23. Guarnera, E.A., Zanzottera, E.M., Pereyra, H., Franco, A.J., 2001. Ultrasonographic diagnosis of ovine cystic echinococcosis. Vet Radiology and Ultrasound 42, 352-354 Hindson, J.C., Winter, A.C., 1990. Outline of clinical diagnosis in sheep. Sevenoaks, Kent, England. Lahmara, S., Ben Chéhidab, F., Pétavyc, A.F., Hammoud, A., Lahmare, J., Ghannayf, A., Gharbib, H.A., Sarcironc, M.E., 2007. Ultrasonographic screening for cystic echinococcosis in sheep in Tunisia. Vet Parasitol 143, 42-49. Lahmara, S., Sarciron, M.E., Chehida, F.B., Hammou, A., Gharbi, H.A., Gherardi, A., Lahmar, J., Pétavy, A.F., 2006. Cystic hydatic disease in sheep: Treatment with percutaneous aspiration and injection with dipeptide methyl ester. Vet Res Comm 30, 379-391. Romanski, K.W., 2004. Ultrasonographic monitoring of gallbladder dynamics during fasting and feeding conditions in sheep. Acta Veterinaria Brno 73, 29-35. Russel, A., 1985 Nutrition of the pregnant ewe. In Practice 7, 23-29. Scott, P.R., 2000. Ultrasonographic examination of the urinary tract of sheep. In Practice 22, 329-334. Scott, P.R. Sheep Medicine. First edition. Manson Publishing, London. (2007). Scott P.R. (2012). Clinical, ultrasonographic and pathological description of bladder distension with consequent hydroureters, severe hydronephrosis and perirenal fluid accumulation in two rams putatively ascribed to pelvic nerve dysfunction. Small Ruminant Research 107: 45-48 Scott, P.R., Collie, D.D.S., Hume, L.H., 1997a. Caseous lymphadenitis in a commercial ram stud in Scotland. The Veterinary Record 141, 548-550. Scott, P.R., Gessert, M.E., Marsh, D., 1997b. Ultrasonographic measurement of the abomasum of neonatal lambs. Vet Rec 141, 524-525. Scott, P.R. & Sargison, N.D. (2001) Extensive ascites associated with vegetative endocarditis in a Blueface Leicester ram. The Veterinary Record 149, 240-241 Scott, P.R. Sargison, N.D., Macrae, A.I., S.R. Rhind (2005) An Outbreak of Subacute Fasciolosis in Soay Sheep: Biochemical, Histological and Ultrasonographic Studies. The Veterinary Journal 170, 325-331 Stoops, S.G., Renshaw, H.W., Thilstead, J.P., 1984. Ovine caseous lymphadenitis: Disease prevalence, lesion distribution, and thoracic manifestation in a population of mature cull sheep from western United States. Am J Vet Res 40, 1110-1114. Whitelaw, A., 1976. Real-time ultrasonic scanning in the diagnosis of pregnancy and the determination of fetal numbers in sheep. Vet Ann 16, 60
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Legends to figures Fig. 1. Ascitic fluid appearing as anechoic area with abdominal viscera displaced dorsally in standing animal; intestines clearly outlined as hyperechoic (bright white) lines/circles, containing material of varying echogenicity. Fig. 2. Extensive peritoneal exudation extending to 16 cm from abdominal wall with broad hyperechoic fibrin strands ,bridging liver and peritoneum, caused by subacute fasciolosis. Fig. 3. Extensive peritoneal with broad hyperechoic fibrin strands, bridging liver and peritoneum, caused by subacute fasciolosis. Fig. 4. Ewe with ‘pear-shaped’ abdomen, as the result of large accumulations of transudate caused by intestinal adenocarcinoma, with transcoelomic spread of the tumour leading to impaired lymphatic drainage and fluid accumulation of transudate. Fig. 5. Accumulations of transudate, caused by intestinal adenocarcinoma, with transcoelomic spread of the tumour causing impaired lymphatic drainage and fluid accumulation. Fig. 6. Dorsal displacement of the intestines by large accumulation of transudate secondary to bacterial endocarditis. Fig. 7. Displacement of liver from the abdominal wall by large accumulation of transudate, secondary to bacterial endocarditis. Fig. 8. Encapsulated 4 cm circular abscess within the omentum. Fig. 9. Sonogram of the caudal abdomen revealing bladder distension, extending to 12 cm in diametre; 5.0 MHz sector scanner. Fig. 10. Sonogram of the caudal abdomen revealing bladder distension, extending to 14 cm in diametre; 5.0 MHz sector scanner. Fig. 11. Confirmation of bladder distension and absence of uroperitoneum seen at post-mortem examination; distended bladder extending along the floor of the abdominal cavity from the pubic symphysis. Fig. 12. Post-mortem examination revealing marked bladder distension, but no uroperitoneum. Fig. 13. A distended bladder readily imaged within the uroperitoneum. Fig. 14. Uroperitoneum revealed at post-mortem examination. Fig 15. Bilateral hydroureter and hydronephrosis, resulting from high urinary backpressure caused by urolithiasis. Fig. 16. Sonogram showing normal right kidney, with hyperechoic line representing the kidney capsule clearly identifiable; 5.0 MHz sector scanner. Fig. 17. Sonogram showing mild (early) hydonephrosis of right kidney; distension of the renal pelvis with urine; 5.0 MHz sector scanner. Fig. 18. Sonogram showing moderate hydonephrosis of right kidney; significant distension (urine) of the renal pelvis, represented by the large anechoic central area; 5.0 MHz sector scanner. 13
Fig. 19. Sonogram showing severe hydonephrosis of the right kidney significant distension (urine) of the renal pelvis, represented by the large anechoic central area; 5.0 MHz sector scanner. Fig. 20. Post-mortem examination confirming severe hydronephrosis of the right kidney (Fig. 19). Fig. 21. Organised haemorrhage, extending approx. 7-8 cm, separating right kidney from abdominal wall (post-mortem findings in Fig. 22). Fig. 22. Haemorrhage extending approx. 7-8 cm, separating right kidney from abdominal wall, seen during post-mortem examination (sonographic findings in Fig. 21). Fig. 23. Organised haemorrhage, extending approx. 5-6 cm, separating right kidney from abdominal wall (post-mortem findings in Fig. 24). Fig. 24. Haemorrhage extending approx. 5-6 cm, separating right kidney from abdominal wall, seen at post-mortem examination (sonographic findings in Fig. 23). Fig. 25. Fluid accumulation surrounding the kidney, appearing as anechoic layer extending to 2-3 cm, with multiple hyperechoic strands, possibly representing fibrin exudate. Fig. 26. Fibrin tags beneath a thick capsule seen at post-mortem examination, with most fluid drained away. Fig. 27. Leakage of urine surrounding the kidney(s) in ram with no overt clinical signs of discomfort or pain. Fig. 28. Presence of fluid containing fibrin strands, separating right kidney from abdominal wall. Fig. 29. Hydronephrosis. Fig. 30. Large (approx. 20 cm in diametre) well-encapsulated fluid-filled mass, containing the right kidney, seen at post-mortem examination; intact bladder wall with no presence of uroperitoneum. Fig. 31. Release of fluid revealed many fibrin tags bridging the wall of the mass and the renal capsule (also in Figs 28 and 29). Fig. 32. Distended bladder and hydroureters, with only the right kidney surrounded by fluid. Fig. 33. Severe hydronephrosis seen at post-mortem examination (also in Fig. 29). Fig. 34. Monitoring by trans-abdominal ultrasonogrpahic examination of an indwelling Foley catheter following a tube cystotomy. Fig. 35. Presence of fibrin clots, typically represented by irregularly shaped hypoechoic circles, 2-4 cm in diametre, with hypechoic dots, within the distended bladder. Fig. 36. Leiomyomas arppearing as large (>14 cm in diametre) uniformly hypoechoic mass, dorsal to the distended fluid-filled (anechoic) bladder. Fig. 37. Ultrasonographic findings confirmed at post-mortem examination; the bladder and leiomyoma have been rotated to the left to more clearly expose the extent of the tumour (the bladder is ventral to the leiomyoma; Fig. 36). Fig. 38. Initial recording of a renal tumour extending to 8 cm from the probe head. Fig. 39. Renal tumour, two months after initial diagnosis, extending to 14 cm from the probe largely caused by accumulations of fluid (Fig. 38). 14
Fig. 40. Renal tumour, four months after initial diagnosis, extending to 16 cm from the probe head, largely caused by accumulations of fluid; ewe in excellent health (Figs 38, 39). Fig. 41. Intra-abdominal haemorrhage at the site of renal tumour; the organised haemorrhage contains some fluid pockets and fibrin clots with some hyperechoic filaments (Figs 38-40). Fig. 42. Intra-abdominal haemorrhage at the site of renal tumour, which has become extensive (Fig. 41), as seen when the ewe was euthanised for welfare reasons, despite normal appetite and no clinical signs of discomfort. Fig. 43. Intra-abdominal haemorrhage at the site of a renal tumour extending to 24 cm (Figs 37-41). Fig. 44. Post-mortem examination findings of a ewe with renal tumour (Figs 37-47); tumour and intraabdominal haemorrhage are enveloped by mesentery. Fig. 45. Post-mortem findings in section of the renal tumour, corresponding well with respective ultrasonographic findings (most of the fluid was released when the kidney was sectioned) (Fig. 40). Fig. 46. Post-mortem findings of intra-abdominal haemorrhage, completely enveloped by mesentery, corresponding well with respective ultrasonographic findings (Figs 41-43). Fig. 47. Clinical presentation of ewe diagnosed with renal tumour: body condition score of 1.0 at initial examination (also in Fig. 48). Fig. 48. Clinical presentation of ewe diagnosed with renal tumour: improvement of body condition (score 3.0) and alertness, with no signs of discomfort or colic (further to Fig. 47); large amount of omental fat seen at post-mortem examination (Suppl. material 16). Fig. 49. Ultrasonographic findings of haemorrhage into the broad ligament, associated with vaginal prolapse, in a ewe at the final stage of gestation. Fig. 50. Post-mortem examination findings of ewe in Fig 4; in utero presence of autolysed lambs.
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S0921-4488(16)30364-9 http://dx.doi.org/doi:10.1016/j.smallrumres.2016.12.013 RUMIN 5371
To appear in:
Small Ruminant Research
Please cite this article as: Scott, P., Abdominal ultrasonography as an adjunct to clinical examination in sheep.Small Ruminant Research http://dx.doi.org/10.1016/j.smallrumres.2016.12.013 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Abdominal ultrasonography as an adjunct to clinical examination in sheep
P. Scott*
Division of Veterinary Clinical Sciences, R(D)SVS, University of Edinburgh, Easter Bush, Roslin, Midlothian, Scotland, EH25 9RG, United Kingdom. *
Corresponding author: [email protected]
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ABSTRACT Modern portable ultrasound machines provide the veterinary clinician with an inexpensive and non-invasive method to further examine sheep on farm, which would take no more than 2-5 minutes with results available immediately. Trans-abdominal ultrasonographic examination provides veterinarians with valuable information regarding bladder distension and uroperitoneum caused by obstructive urolithiasis, which greatly facilitates prompt corrective surgery. Advanced hydronephrosis, which affords a grave prognosis for urolithiasis cases, is readily identified by an increased renal pelvis and thinned cortex. Unless caused by large numbers of migrating immature liver flukes, accumulation of inflammatory exudate in the peritoneal cavity is uncommon in sheep. Unlike cattle, infection arising from the gastrointestinal tract, e.g., traumatic reticuloperitonitis, is rare in sheep. Renal, intestinal, kidney and bladder tumours can be identified during ultrasonographic examination, but these conditions affect individual sheep and are not a significant flock problem.
Keywords: abdomen, fasciolosis, hydronephrosis, sheep, ultrasonography, urolithiasis..
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1. Introduction Urethral obstruction occurs occasionally in mature rams with most calculi lodging within the vermiform appendix (Kümper, 1994; Scott, 2000); obstruction proximal to the sigmoid flexure is less common. Early recognition of clinical signs of dysuria and stranguria by the farmer and prompt veterinary treatment are essential to ensure a satisfactory outcome, because irreversible hydronephrosis quickly results from urinary back pressure (Kümper, 1994; Biricik et al., 2003). Early diagnosis has allowed surgical correction of breeding rams by tube cystotomy (Cockcroft, 1993) and rapid implementation of control measures (Angus, 2000) to prevent further cases. While rupture of the urethra can occur in urolithiasis cases with subcutaneous accumulation of urine along the ventral abdominal wall, rupture of the bladder is rare (Scott, 2000; Scott, 2007), except for neglected cases (Kümper, 1994). Marked urinary bladder distension, hydronephrosis and perirenal fluid accumulation were identified ultrasonographically in two rams from the same farm. Both rams were observed to urinate, but flow rate of urine was estimated to be smaller than normal and duration of urination was reduced to around 5to 10 seconds, when around 20 to 30 seconds is considered normal. There was normal tail and rectal tone and normal perineal and pelvic limb reflexes. A presumptive diagnosis of pelvic nerve dysfunction causing detrusor atony and bladder distension with secondary pressure-induced hydronephrosis had been suggested, but could not be proved; detailed dissection at post-mortem examination found no evidence of urethral obstruction (Scott, 2012). This diagnosis had become only possible after combining clinical and ultrasonographic findings; post-mortem examination would most likely have yielded a diagnosis of obstructive urolithiasis. Urinary tract infections leading to pyelonephritis are rare in sheep, with the exception of the cases of male animals, which have undergone subischial urethrostomy surgery to bypass the site of obstructive urolithiasis. Biricik et al. (2003) have concluded from their studies on young lambs with obstructive urolithiaisis that B-mode and colour-coded Doppler sonography might provide useful information for detection of changes in kidneys, e.g., hydronephrosis or renal swelling, as well as elevated resistance in the renal interlobar artery. While hepatocellular tumours are not uncommon in old sheep, such lesions are usually only recognised at the slaughter plant in ewes culled for poor condition; however, Lofstedt et al. (1988) have reported that liver tissue obtained via ultrasound-guided percutaneous liver biopsy had suggested a diagnosis of adenocarcinoma of the liver, later confirmed at post-mortem examination. Large liver abscesses caused by Corynebacterium pseudotuberculosis, the causal agent of caseous lymphadenitis, are not uncommon in many countries, including the USA (Stoops et al., 1984; Gnad et al., 2000). In cases with large liver abscesses, these can be readily identified during ultrasonographic examination (Scott et al., 1997a). 3
Ultrasonographic examination of the liver has confirmed the presence of hydatid cysts therein and its potential use as a mass screening approach for cystic echinococcosis (Lahmara et al., 2007); a similar conclusion was reported by Guarnera et al. (2001). Cysts of Echinococcus granulosus in the liver of sheep were localised by ultrasonographic examination and injected with dipeptide methyl ester and the treatment response monitored by imaging (Lahmara et al., 2006). Hepatomegaly and the demonstration of multiple hyperechoic dots within the hepatic parenchyma, representing accumulations of inflammatory cells, have been reported in sheep with subacute fasciolosis (Scott et al., 2004) and these lesions resolved within one month of treatment with triclabendazole. Romanski (2004) reported gall bladder dimensions measured ultrasonographically in sheep after various intervals during fasting with a doubling of volume after two days and suggested that such measurement could provide important clinical information. These data support the post-mortem findings of gall bladder distension in cachectic sheep. While ultrasound-guided aspiration of bile from the gall bladder has been recommended for detection of fluke eggs in cattle (Braun et al., 1996), such examinations are not necessary to establish a diagnosis of patent fascioliasis in sheep, because the coproantigen ELISA test permits much earlier recognition by identifying immature fluke infestation. Perinatal lamb mortality, defined as losses within the first three days of life, is the major cause of lamb deaths with estimates ranging from 10 to 25 per cent (Whitelaw, 1976; Eales et al., 1982; Barlow et al., 1987; Hindson and Winter, 1990). Ultrasonographic examination of the abomasum of neonatal lambs provides an immediate indication to the veterinary investigator whether lambs have sucked. The difference in lamb abomasal diametre before and after sucking is so large, 3 versus 8 to 10 cm, that minor errors in individual lamb recordings would not affect the collection of meaningful data from 20 or more lambs and their interpretation (Scott et al., 1997b).
2. Methodology for ultrasonographic examination 2.1. Bladder and ventral abdomen
The absence of fleece in the inguinal area expedites site preparation, when examining the ventral and caudal abdomen in sheep. Ultrasonographic examination of the bladder and the caudal abdomen are undertaken in the standing animal, using either 5.0 MHz linear array or (micro-convex) sector scanners. The caudal abdomen is examined for the bladder and gravid uterus and increased peritoneal fluid. The right inguinal region immediately cranial to the pubis is cleaned using a mild detergent solution diluted in warm tap water to remove superficial grease and debris. The right inguinal region is chosen, because the left side of the abdomen is largely occupied by the rumen. Ultrasound gel is applied to the probe head. The transducer head is directed toward the animal’s tail head to image the bladder. When the bladder is enlarged, an estimate of its size can be obtained by moving a 5.0 MHz linear scanner (field 4
depth of 10.0 cm) cranially along the ventral midline from the level of the pubic symphysis, because of its cylindrical rather than spherical shape when distended.
2.2. Right kidney
Examination of the right kidney necessitates shaving the fleece from the right sublumbar fossa immediately caudal to the last rib. The sector transducer head is firmly held against the skin to ensure good visualisation of the right kidney juxtaposed the caudal lobe of the liver. Advanced hydronephrosis can be identified by the grossly increased renal pelvis, which is represented by the anechoic (fluid-filled) centre of the kidney. It is not always possible to scan the left kidney in sheep via the flank; however, such examination is not necessary, as the urinary tract obstruction is distal to the ureters, therefore the disorder affects both kidneys equally.
2.3. Liver
The liver can be imaged from the seventh to eleventh intercostal spaces halfway down the right chest wall, and sometimes immediately caudal to the costal arch at this level with the 5.0-6.5 MHz sector probe head pointed towards the contralateral shoulder (Scott et al., 2005). Hepatocellular tumours are not uncommon in old sheep. Such lesions are usually only recognised at the slaughter plant in ewes culled for poor condition
2.4. Abomasal diametre of neonatal lambs
The abomasal diametre of neonatal lambs can be measured using a 5.0 MHz sector scanner applied at right angles to the abdominal wall at the umbilicus. The abomasum can be clearly identified as a hypoechoic area delineated by a hyperechoic wall. The vertical distance is measured between the probe head and the far abomasal wall.
3. Ultrasonographic findings 3.1. Ascites
There is scant peritoneal fluid in normal sheep, which may not be visualised during ultrasonographic examination. Ascitic fluid appears as an anechoic area with abdominal viscera displaced dorsally in the standing animal. The intestines are clearly outlined as hyperechoic (bright white) lines/circles containing material of varying echogenicity (Fig. 1; Suppl. material 1). By 5
maintaining the probe head in the same position, digesta can be visualised as multiple small dots of varying echogenicity forcibly propelled within the intestines.
3.2. Peritonitis
With the exception of subacute fasciolosis (Figs 2, 3), significant peritoneal effusion/exudation is rarely seen in sheep with the reaction limited by the omentum to focal fibrinous/fibrous adhesions and localised accumulations of peritoneal exudate. The most common exception is intestinal adenocarcinoma, where transcoelomic spread of the tumour causes impaired lymphatic drainage and accumulation of transudate (Figs 4, 5). A large accumulation of transudate is also common in some cases of bacterial endocarditis (Figs 6, 7). Abscesses within the peritoneal cavity are rapidly enveloped by the omentum (Fig. 8). The peritoneal abscess appears as a circular anechoic area containing multiple hypechoic dots surrounded by an anechoic capsule (Fig. 8; Suppl. material 2); the contents are static, which differentiates this structure from a cross section of intestine.
3.3. Urinary tract
The urinary bladder is not usually imaged during trans-abdominal ultrasonographic examination in normal sheep, because it is contained within the pelvic canal. When distended with urine, the bladder extends 6 to 10 cm in diametre cranial to the pelvic brim in 20 to 50 kg growing lambs (Fig. 9; Suppl. material 3, 4) and 12 to 20 cm in diametre in mature rams (Fig. 10). The bladder wall appears as a hyperechoic circle; oedema of the wall results in widening of this white line. Rupture of the bladder does not occur (Figs 11, 12), except for neglected cases and even then urine leaks across the taut bladder wall rather than true rupture (Suppl. material 5, 6). In such cases, the distended bladder can be imaged within the uroperitoneum (Figs 13, 14). Fibrin tags can sometimes be visualised within the uroperitoneum as fine hyperechoic filaments within the anechoic fluid. Significant hydronephrosis develops after high urinary backpressure of 5 to 7 days’ duration, therefore ultrasonographic examination of the right kidney should be undertaken at the same time (Suppl. material 7). This period is based on the author’s ultrasonographic and post-mortem findings, often at the time of presentation, and therefore relies upon an accurate assessment of the duration of illness reported by the owner, which may be an underestimation in many cases. High urinary backpressure leads to hydroureters and hydronephrosis (Fig. 15). The sector transducer head is firmly held against the skin to ensure good visualisation of the right kidney juxtaposed the caudal lobe of the liver (Fig. 16; Suppl. material 8, 9). Early stages of disorders (Fig. 17; Suppl. material 10, 11) may be difficult to interpret with respect to prognosis, but it is useful to ascertain that there is no advanced hydronephrosis. Advanced hydronephrosis can be readily 6
identified by the grossly increased renal pelvis, which is represented by the anechoic (fluid-filled) centre of the kidney (Figs 17-20; Suppl. material 12). Haemorrhage surrounding the kidney has resulted in displacement of the right kidney from the abdominal wall (Figs 21-24; Suppl. material 13). Clot formation results in broad hyperechoic strands within the anechoic serum. Fluid accumulation surrounding the kidney appears as an anechoic layer extending to 2 to 3 cm (Fig. 25), where there is obvious hydronephrosis confirmed at post-mortem examination (Fig. 26; Suppl. material 14). Presence of hydronephrosis due to high urinary backpressure would suggest that this fluid would likely be urine, but this cannot be determined from the sonogram alone. Leakage of urine surrounding the kidney(s) may not cause obvious clinical signs (Fig. 27) and trans-abdominal ultrasonographic examination may reveal surprising pathology (Fig. 28-33), whereby there is 12-13 cm of fluid separating the right kidney from the abdominal wall (Fig. 28) containing fibrin strands. There is obvious hydronephrosis (Fig. 29) with these sonographic findings confirmed at postmortem examination (Figs 30-33). There is marked distension of both ureters (hydroureters) and distension of the bladder (Fig. 32), which has not ruptured nor is there uroperitoneum; no reason was found to explain why fluid (urine) was present surrounding only the right kidney. The findings reported here and featured in Fig. 21-33 indicate that ultrasonographic examination of the right kidney must be undertaken before attempted surgical correction of urolithiasis. Ultrasonographic monitoring of the indwelling Foley catheter can be undertaken following tube cystotomy (Fig. 34; Suppl. material 15)
3.4. Cystitis
In cystitis, the bladder wall appears thicker than normal with fibrin tags on the mucosal surface, which appear as hyperechoic strands. Large fibrin clots, typically represented by irregularly shaped 2 to 4 cm diametre hypoechoic circles containing hyperechoic dots, may be present within the distended bladder (Fig. 35).
3.5. Leiomyoma
Leiomyomas are not commonly observed in sheep and would appear as a large (>14 cm) uniformly hypoechoic mass dorsal to the bladder (Figs 36, 37).
3.6. Renal tumour
Renal tumours have been rarely reported in sheep. Development of a renal tumour over three months is shown sequentially (Figs 38-40; Suppl. material 16), during which time the tumour increased 7
in size from 8 cm to 16 cm in diametre. Intra-abdominal haemorrhage was identified after two months, which became extensive one month later, when the ewe was euthanised for welfare reasons (Figs 4146; Suppl. material 16). It is important to recognise that the ewe was clinically normal throughout this period and had a normal appetite and its welfare was not compromised; indeed, body condition increased from a score of 1.0 at admission (scale 1-5; Fig. 46) to 3.0 at the time of euthanasia (Fig. 47); a large amount of omental fat was evident at post-mortem examination (Suppl. material 16). The provisional diagnosis was pyelonephritis (urinalysis revealed the presence of blood, protein and white cells) and the sheep was treated with procaine penicillin daily for three weeks. Diagnosis could not be made on clinical examination alone, hence the ultraonographic findings can be used by veterinarians when presented with similar images.
3.7. Liver
Unlike cattle, liver abscesses have not been identified in sheep by this author. Furthermore, examination of the liver in ewes with pregnancy toxaemia has failed to identify consistent sonographic changes. Gall bladder distension (Suppl. material 17) and nodular hyperplasia (Suppl. material 18) have been identified in individual ewes with chronic fasciolosis.
3.8. Miscellaneous conditions
3.8.1. Intra-abdominal haemorrhage Haemorrhage into the broad ligament can occur in cases of vaginal prolapse (Figs 48, 49).
3.8.2. Diaphragmatic hernia Diaphragmatic hernia has been observed in three ewes with no history of severe trauma. Examination of the normal side of the chest (Suppl. material 19) revealed that the heart pressed against the chest wall; the presence of intestines in the contralateral chest cavity confirms the diaphragmatic hernia (Suppl. material 20).
4. Discussion Many farm animal practitioners use 5.0 MHz linear array scanners for early pregnancy diagnosis in cattle, but this equipment may also be used to examine abdominal viscera in sheep, albeit the depth of field is limited to 10 cm. Examination using the 5.0 MHz linear array scanner may underestimate the size of the distended bladder, but this does not affect the diagnosis, nor the immediate action of the veterinary surgeon to examine the ram’s vermiform appendage for obstruction. A 5.0 MHz sector (microconvex) scanner is necessary to image the right kidney for hydronephrosis. 8
Recording of ultrasonographic findings on to a laptop or other suitable mobile storage device is strongly recommended, because it allows the veterinarian to accurately monitor changes over time, including response to treatments, and to retrospectively analyse sonographic findings should the animal be examined post-mortem, due to advanced disease or another reason, e.g., animal welfare concerns. Increasingly, digital information, e.g., images or video recordings of problem cases, can be e-mailed to experts for immediate interpretation. Such dialogue and dissemination of field data benefits both parties. Publication of such findings should be more actively encouraged. Post-mortem examination findings have been included in figures and in the video recordings in this article to aid interpretation of the sonograms.
4.1. Ascites
Large accumulations of peritoneal fluid are uncommon in sheep, even in those animals with profound hypoalbuminaemia caused by either paratuberculosis or severe parasitism, e.g., haemonchosis or chronic fasciolosis. Unlike cattle, ascites secondary to right-sided heart failure is rare in sheep, but has been reported secondary to bacterial endocarditis (Scott and Sargison, 2001). A large accumulation of peritoneal fluid in older sheep is often caused by impaired lymphatic drainage subsequent to transcoelomic spread of intestinal adeoncarcinoma (Scott, 2007). Accumulation of peritoneal exudate and/or peritonitis arising from lesions in the gastrointestinal tract, e.g., traumatic reticulitis or abomasal ulceration/perforation is uncommon in sheep. Whilst uterine tears can give rise to extensive accumulation of peritoneal exudate in cattle, such pathology is rare in sheep and may be related to the more extensive tears suffered by sheep leading to rapid death.
4.2. Bladder and kidney
While marked elevations of blood urea nitrogen and creatinine concentrations occur as a result of partial or complete urethral obstruction, such increases are not pathognomonic and there are no recognised threshold concentrations above which urolithiasis can be confirmed. Examination using a 5.0 MHz linear array scanner readily identifies distended bladder and uroperitoneum if present, but the true size of the bladder may not be measured, because it may extend to 20 cm in diametre, thereby exceeding the 10 cm field of many linear array scanners. It must be remembered that the bladder in normal male sheep is largely contained within the bony pelvis, therefore presence of the bladder extending for up to 10 cm or more over the pelvic brim is abnormal, determination of the actual size of the bladder is of secondary importance (Scott, 2000). High urinary back pressure results in marked hydronephrosis in approximately 5 to 7 days with an associated grave prognosis, but there are insufficient published data on renal measurements to decide whether a tube cystotomy should be undertaken. Interpretation of gross findings at post-mortem 9
examination has suggested that the rams featured in Figs 17-19 would have been highly unlikely to recover should surgery had been performed. Marked urinary bladder distension, hydronephrosis and perirenal fluid accumulation were identified ultrasonographically in two rams without obvious urethral obstruction leading to a presumptive diagnosis of pelvic nerve dysfunction causing detrusor atony and bladder distension with secondary pressure-induced hydronephrosis (Scott, 2012). This diagnosis was only possible after combining clinical and ultrasonographic findings; post-mortem examination would most likely have yielded a diagnosis of obstructive urolithiasis.
4.3. Liver
Ultrasonographic examination of the liver has limited application in small ruminant practice. Fatty infiltration of the liver cannot be reliably detected and preventive measures for ovine pregnancy toxaemia are best implemented by assessment of ewes’ nutritional regime 5 to 6 weeks before the anticipated lambing date (Russel, 1985), coupled with measurements of β-hydroxybutyrate blood concentrations in pregnant animals in the flocks. Whilst there are characteristic sonographic changes in the liver caused by developing liver flukes, control measures are much more important, which are based upon perceived risk following analysis of meteorological data over the summer months. Routine preventive flukicide treatments are practiced by sheep farmers in endemic fluke areas, where treatment efficacy can be assessed by measuring faecal coproantigen ELISA concentrations, especially where triclabendazole resistance is suspected.
4.4. Vaginal prolapse
Complications to vaginal prolapse may include haemorrhage into the broad ligament. This can be detected by transabdominal ultrasonographic examination and may require an emergency caesarean operation to correct such problems, but there are no such reports in the literature.
5. Concluding remarks In summary, trans-abdominal ultrasonographic examination is most usefully employed to support a provisional clinical diagnosis of urolithiasis and to investigate whether there is significant hydronephrosis ahead of tube cystotomy surgery. Other complications, e.g., perirenal haemorrhage and accumulation(s) of exudate, can also be detected sonographically. The high financial value of stud rams allows such further examination, which is rarely afforded for other conditions in commercial-value sheep. The examination costs only the veterinary practitioner’s time, but can often provide immediate clinical information allowing either prompt treatment/surgery or euthanasia for welfare reasons due to 10
a hopeless prognosis. The greater availability of excellent quality ultrasound probes at relatively low cost allows exciting diagnostic possibilities for all small ruminant practitioners.
Conflict of interest statement The author of this paper has no financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper.
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References Angus KW, 2000. Diseases of the urinary tract, in Martin WB, Aitken ID (eds): Diseases of sheep. Blackwell Science, Oxford, UK, pp 344-351. Barlow, R.M., Gardiner, A.C., Angus, K.W., Gilmour, J.S., Mellor, D.J., Cuthbertson, J.C., Newlands, G., Thompson, R., 1987. Clinical, biochemical and pathological study of perinatal lambs in a commercial flock. Vet Rec 120: 357, 1987. Biricik, H.S., Çimtay, I., Öztürk, A., Aksoy, G., 2003. B-Mode and colour coded doppler sonography of kidneys in lambs with urolithiasis and in healthy lambs. Deutsche Tierarztliche Wochenschrift 110. 502-505. Braun, U., Pusterla, N., Wild, K., 1996. Ultrasonographic examination of the liver and gallbladder in cows: Abnormal findings. Compendium on Continuing Education for the Practicing Veterinarian 18, 1255-1269. Cockcroft, P.D., 1993. Dissolution of obstructive urethral urolithiasis in a ram. Vet Rec 132, 486-487. Eales, F.A., Gilmour, J.S., Barlow, R.M., Small, J., 1982. Causes of hypothermia in 89 lambs. Vet Rec 110, 118120. Gnad, D.P., Van Metre, D.C., Angelos, S.M., Spaeth, C., 2000. Diagnosing weight loss in sheep: A practical approach. Compend Contin Educ Pract Vet 22, S16-23. Guarnera, E.A., Zanzottera, E.M., Pereyra, H., Franco, A.J., 2001. Ultrasonographic diagnosis of ovine cystic echinococcosis. Vet Radiology and Ultrasound 42, 352-354 Hindson, J.C., Winter, A.C., 1990. Outline of clinical diagnosis in sheep. Sevenoaks, Kent, England. Lahmara, S., Ben Chéhidab, F., Pétavyc, A.F., Hammoud, A., Lahmare, J., Ghannayf, A., Gharbib, H.A., Sarcironc, M.E., 2007. Ultrasonographic screening for cystic echinococcosis in sheep in Tunisia. Vet Parasitol 143, 42-49. Lahmara, S., Sarciron, M.E., Chehida, F.B., Hammou, A., Gharbi, H.A., Gherardi, A., Lahmar, J., Pétavy, A.F., 2006. Cystic hydatic disease in sheep: Treatment with percutaneous aspiration and injection with dipeptide methyl ester. Vet Res Comm 30, 379-391. Romanski, K.W., 2004. Ultrasonographic monitoring of gallbladder dynamics during fasting and feeding conditions in sheep. Acta Veterinaria Brno 73, 29-35. Russel, A., 1985 Nutrition of the pregnant ewe. In Practice 7, 23-29. Scott, P.R., 2000. Ultrasonographic examination of the urinary tract of sheep. In Practice 22, 329-334. Scott, P.R. Sheep Medicine. First edition. Manson Publishing, London. (2007). Scott P.R. (2012). Clinical, ultrasonographic and pathological description of bladder distension with consequent hydroureters, severe hydronephrosis and perirenal fluid accumulation in two rams putatively ascribed to pelvic nerve dysfunction. Small Ruminant Research 107: 45-48 Scott, P.R., Collie, D.D.S., Hume, L.H., 1997a. Caseous lymphadenitis in a commercial ram stud in Scotland. The Veterinary Record 141, 548-550. Scott, P.R., Gessert, M.E., Marsh, D., 1997b. Ultrasonographic measurement of the abomasum of neonatal lambs. Vet Rec 141, 524-525. Scott, P.R. & Sargison, N.D. (2001) Extensive ascites associated with vegetative endocarditis in a Blueface Leicester ram. The Veterinary Record 149, 240-241 Scott, P.R. Sargison, N.D., Macrae, A.I., S.R. Rhind (2005) An Outbreak of Subacute Fasciolosis in Soay Sheep: Biochemical, Histological and Ultrasonographic Studies. The Veterinary Journal 170, 325-331 Stoops, S.G., Renshaw, H.W., Thilstead, J.P., 1984. Ovine caseous lymphadenitis: Disease prevalence, lesion distribution, and thoracic manifestation in a population of mature cull sheep from western United States. Am J Vet Res 40, 1110-1114. Whitelaw, A., 1976. Real-time ultrasonic scanning in the diagnosis of pregnancy and the determination of fetal numbers in sheep. Vet Ann 16, 60
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Legends to figures Fig. 1. Ascitic fluid appearing as anechoic area with abdominal viscera displaced dorsally in standing animal; intestines clearly outlined as hyperechoic (bright white) lines/circles, containing material of varying echogenicity. Fig. 2. Extensive peritoneal exudation extending to 16 cm from abdominal wall with broad hyperechoic fibrin strands ,bridging liver and peritoneum, caused by subacute fasciolosis. Fig. 3. Extensive peritoneal with broad hyperechoic fibrin strands, bridging liver and peritoneum, caused by subacute fasciolosis. Fig. 4. Ewe with ‘pear-shaped’ abdomen, as the result of large accumulations of transudate caused by intestinal adenocarcinoma, with transcoelomic spread of the tumour leading to impaired lymphatic drainage and fluid accumulation of transudate. Fig. 5. Accumulations of transudate, caused by intestinal adenocarcinoma, with transcoelomic spread of the tumour causing impaired lymphatic drainage and fluid accumulation. Fig. 6. Dorsal displacement of the intestines by large accumulation of transudate secondary to bacterial endocarditis. Fig. 7. Displacement of liver from the abdominal wall by large accumulation of transudate, secondary to bacterial endocarditis. Fig. 8. Encapsulated 4 cm circular abscess within the omentum. Fig. 9. Sonogram of the caudal abdomen revealing bladder distension, extending to 12 cm in diametre; 5.0 MHz sector scanner. Fig. 10. Sonogram of the caudal abdomen revealing bladder distension, extending to 14 cm in diametre; 5.0 MHz sector scanner. Fig. 11. Confirmation of bladder distension and absence of uroperitoneum seen at post-mortem examination; distended bladder extending along the floor of the abdominal cavity from the pubic symphysis. Fig. 12. Post-mortem examination revealing marked bladder distension, but no uroperitoneum. Fig. 13. A distended bladder readily imaged within the uroperitoneum. Fig. 14. Uroperitoneum revealed at post-mortem examination. Fig 15. Bilateral hydroureter and hydronephrosis, resulting from high urinary backpressure caused by urolithiasis. Fig. 16. Sonogram showing normal right kidney, with hyperechoic line representing the kidney capsule clearly identifiable; 5.0 MHz sector scanner. Fig. 17. Sonogram showing mild (early) hydonephrosis of right kidney; distension of the renal pelvis with urine; 5.0 MHz sector scanner. Fig. 18. Sonogram showing moderate hydonephrosis of right kidney; significant distension (urine) of the renal pelvis, represented by the large anechoic central area; 5.0 MHz sector scanner. 13
Fig. 19. Sonogram showing severe hydonephrosis of the right kidney significant distension (urine) of the renal pelvis, represented by the large anechoic central area; 5.0 MHz sector scanner. Fig. 20. Post-mortem examination confirming severe hydronephrosis of the right kidney (Fig. 19). Fig. 21. Organised haemorrhage, extending approx. 7-8 cm, separating right kidney from abdominal wall (post-mortem findings in Fig. 22). Fig. 22. Haemorrhage extending approx. 7-8 cm, separating right kidney from abdominal wall, seen during post-mortem examination (sonographic findings in Fig. 21). Fig. 23. Organised haemorrhage, extending approx. 5-6 cm, separating right kidney from abdominal wall (post-mortem findings in Fig. 24). Fig. 24. Haemorrhage extending approx. 5-6 cm, separating right kidney from abdominal wall, seen at post-mortem examination (sonographic findings in Fig. 23). Fig. 25. Fluid accumulation surrounding the kidney, appearing as anechoic layer extending to 2-3 cm, with multiple hyperechoic strands, possibly representing fibrin exudate. Fig. 26. Fibrin tags beneath a thick capsule seen at post-mortem examination, with most fluid drained away. Fig. 27. Leakage of urine surrounding the kidney(s) in ram with no overt clinical signs of discomfort or pain. Fig. 28. Presence of fluid containing fibrin strands, separating right kidney from abdominal wall. Fig. 29. Hydronephrosis. Fig. 30. Large (approx. 20 cm in diametre) well-encapsulated fluid-filled mass, containing the right kidney, seen at post-mortem examination; intact bladder wall with no presence of uroperitoneum. Fig. 31. Release of fluid revealed many fibrin tags bridging the wall of the mass and the renal capsule (also in Figs 28 and 29). Fig. 32. Distended bladder and hydroureters, with only the right kidney surrounded by fluid. Fig. 33. Severe hydronephrosis seen at post-mortem examination (also in Fig. 29). Fig. 34. Monitoring by trans-abdominal ultrasonogrpahic examination of an indwelling Foley catheter following a tube cystotomy. Fig. 35. Presence of fibrin clots, typically represented by irregularly shaped hypoechoic circles, 2-4 cm in diametre, with hypechoic dots, within the distended bladder. Fig. 36. Leiomyomas arppearing as large (>14 cm in diametre) uniformly hypoechoic mass, dorsal to the distended fluid-filled (anechoic) bladder. Fig. 37. Ultrasonographic findings confirmed at post-mortem examination; the bladder and leiomyoma have been rotated to the left to more clearly expose the extent of the tumour (the bladder is ventral to the leiomyoma; Fig. 36). Fig. 38. Initial recording of a renal tumour extending to 8 cm from the probe head. Fig. 39. Renal tumour, two months after initial diagnosis, extending to 14 cm from the probe largely caused by accumulations of fluid (Fig. 38). 14
Fig. 40. Renal tumour, four months after initial diagnosis, extending to 16 cm from the probe head, largely caused by accumulations of fluid; ewe in excellent health (Figs 38, 39). Fig. 41. Intra-abdominal haemorrhage at the site of renal tumour; the organised haemorrhage contains some fluid pockets and fibrin clots with some hyperechoic filaments (Figs 38-40). Fig. 42. Intra-abdominal haemorrhage at the site of renal tumour, which has become extensive (Fig. 41), as seen when the ewe was euthanised for welfare reasons, despite normal appetite and no clinical signs of discomfort. Fig. 43. Intra-abdominal haemorrhage at the site of a renal tumour extending to 24 cm (Figs 37-41). Fig. 44. Post-mortem examination findings of a ewe with renal tumour (Figs 37-47); tumour and intraabdominal haemorrhage are enveloped by mesentery. Fig. 45. Post-mortem findings in section of the renal tumour, corresponding well with respective ultrasonographic findings (most of the fluid was released when the kidney was sectioned) (Fig. 40). Fig. 46. Post-mortem findings of intra-abdominal haemorrhage, completely enveloped by mesentery, corresponding well with respective ultrasonographic findings (Figs 41-43). Fig. 47. Clinical presentation of ewe diagnosed with renal tumour: body condition score of 1.0 at initial examination (also in Fig. 48). Fig. 48. Clinical presentation of ewe diagnosed with renal tumour: improvement of body condition (score 3.0) and alertness, with no signs of discomfort or colic (further to Fig. 47); large amount of omental fat seen at post-mortem examination (Suppl. material 16). Fig. 49. Ultrasonographic findings of haemorrhage into the broad ligament, associated with vaginal prolapse, in a ewe at the final stage of gestation. Fig. 50. Post-mortem examination findings of ewe in Fig 4; in utero presence of autolysed lambs.
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