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Anorectal Abscess Fistula
Symposium on Colon and Anorectal Surgery
Anorectal Abscess Fistula
Patrick H. Hanley, M.D. *
Suppurative anorectal disease, such as abscess-fistula-in-ano, is an anatomic alteration and thus requires a thorough knowledge of the anatomy and structures surrounding the anorectum to enable early diagnosis and appropriate treatment.
ANATOMICAL BASIS The anorectum is 4 cm in length. The dentate or mucocutaneous line demarcates the junction of the lower rectum with the anal canal. Two cm proximal to the dentate line to the level of the anorectal ring (puborectalis muscle) is the lower rectum. Two cm distal to the dentate line to the anal verge is the anal canal. The anorectum is formed by the embryonic fusion of mesodermal, endodermal, and ectodermal tissues to form the intricate trilaminar arrangement of tissue planes that are of special pathological significance in suppurative diseases. The junction of the proctodeum with the blind pouch of the rectum forms the dentate line; however, the modified stratified squamous epithelium of the anal canal may override the columnar rectal mucosal epithelium, so that the dentate line does not sharply demarcate the epithelial junction. The pecten in, the upper third of the anal canal between the dentate line and the intersphincteric line is 3 to 7 mm in width. The subepithelial tissue space of the pecten is continuous with the submucosa of the lower rectum. It may contain anal glands which drain into the rectum through the anal crypts of Morgagni. The dentate line and the pecten area is the site of anastomosis of the hemorrhoidal circulation, the somatic and visceral lymphatics, and the cerebrospinal and sympathetic nerve supply of the anorectum. The blind pouch of the rectum descends anterior to the puborectalis and through the deep and superficial external sphincter. The cir"Emeritus Clinical Professor of Surgery, Tulane University School of Medicine, New Orleans; Senior Surgeon and Former Head, Department of Colon and Rectal Surgery, Ochsner Medical Institutions, New Orleans, Louisiana
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cular muscle of the lower rectum enlarges to form the internal sphincter which surrounds the upper two thirds of the anorectum and is a strong barrier that influences the direction of spread of intermuscular abscesses. It extends from the puborectalis to the intersphincteric line. The puborectalis portion of the levator has its origin from the pubic bones and forms a sling about the upper limits of the anorectum. It is an important landmark in the treatment of fistula-in-ano. Immediately below the puborectalis, the deep component of the external sphincter completely encircles the upper third of the internal sphincter. The superficial external sphincter has its origin from the posterior surface of the coccyx and, upon reaching the posterior anorectum, divides into halves to give the anorectum a strong lateral support. It converges anteriorly to insert in the central tendon of the perineum. The subcutaneous portion of the external sphincter muscle encircles the lower third of the anorectum. The longitudinal muscle of the rectum separates the internal sphincter from the external sphincters. It receives fibers from the puborectalis at the anorectal ring to form the fibroelastic conjoined longitudinal muscle. Some of its fibers insert into all external sphincter components. At the lower level of the internal sphincter, it divides into a medial portion that inserts into the anal skin at the intersphincteric line and a lateral portion that passes between the superficial and the subcutaneous external sphincter muscles and extends laterally to insert into the. tuberosity of the ischium separating the ischiorectal fossa from the perianal spaces.
CLASSIFICATION Eisenhammer,4-7 Parks,2° and Harkins,16 emphasized that infection of anal glands in the space between the internal sphincter and the longitudinal muscle of the rectum is, with few exceptions, the cause of anorectal abscess, and the consensus is that anorectal abscess and fistula-in-ano are stages of the same condition. Therefore, initially an anorectal abscess is located in a specific anorectal space. This concept supports a new classification for anorectal space abscess and fistulain-ano based on the precise anatomic site of origin of the initial anorectal infection and the pathway of spread if not treated as a surgical emergency (Table 1). With few exceptions, abscess of the anorectum begins in the intermuscular space between internal sphincter and longitudinal muscles of the rectum. If the pus remains below the level of the anorectal ring, it is a low intermuscular abscess (Fig. 1). If untreated, it will rupture transphincterically to involve one of the infralevator anorectal spaces. If the intermuscular abscess extends upward above the anorectal ring, it is classified as a high intermuscular abscess (Fig. 2), and if untreated, it will either rupture through the longitudinal muscles to involve the supralevator spaces or into the rectum. In rare instances, the intermuscular abscess may result in combinations of infralevator transsphincteric and supralevator abscess-fistula-in-ano. The anal glands are
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Table 1.
Classification of Anorectal Abscess and Fistula-in-Ano
I. Low Intermuscular Abscess A. Infralevator- Transsphincteric 1. Perianal space 2. Superficial postanal space 3. Superficial anterior anal space 4. Deep postanal space (horseshoe) 5. Deep anterior anal space (horseshoe) 6. Ischiorectal fossae II. High Intermuscular Abscess A. Supralevator 1. Retrorectal space 2. Rectovesical space 3. Pelvirectal space III. Intermuscular abscess with combined supralevator and infralevator abscess IV. Subcutaneous anal canal space V. Submucosal rectal space
located primarily in the posterior and anterior quadrants of the anorectum; therefore, intermuscular abscesses are rarely seen laterally. Some intermuscular abscesses originate from active chronic anal fissure. This article will discuss only anorectal abscess fistulas due to infected anal glands. However, in the differential diagnosis of any sinus opening about the anus, one must consider infected presacral epidermoid inclusion cysts,10, 12 infected sebaceous cysts, hidradenitis suppurativa, furunculosis, penetrating wounds, foreign bodies, traumatic injuries, Crohn's disease, ulcerative colitis, diverticulitis, Bartholin abscesses, and postoperative complications.
SYMPTOMS Symptoms of intermuscular abscess are, at the onset, a dull, aching pain in the rectum (increasing in severity rapidly as the anorectal spaces become involved), chills, and fever. Digital rectal examination during the first two or three days will reveal an exquisitely tender, elongated, tense swelling in the intermuscular space (Figs. 1 and 2). If the abscess is not drained early, the symptoms progressively get worse.
SURGICAL TREATMENT The consensus of surgeons is that there is no place for conservative medical treatment of anorectal abscesses; they are all surgical emergencies. The treatment of an early intramuscular space abscess is to insert a probe through the primary opening, passing it cephalad into the abscess cavity,. and then to do a complete internal sphincterotomy, over the probe, with the electrosurgical unit (coagulating cur-
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Ext. Sph.
Fig. 1
Ext. Sph.
Fig. 2 Figure 1. Low intramuscular abscess descends to the medial termination of the longitudinal muscle of the rectum. It is below the level of the puborectalis. Figure 2. High intramuscular abscess dissects cephaled extending above the level of the puborectalis muscle.
rent). The abscess will drain into the rectum. Occasionally, it may be necessary to continue the incision downward to sever the subcutaneous external sphincter for better drainage. Severing the subcutaneous external sphincter anteriorly is contraindicated in the female patient. Early treatment under anesthesia will prevent the possible development of supralevator or infralevator trans sphincteric involvement and formation of a fistula-in-ano. Between 1950 and 1976 at Ochsner Clinic, we treated 840 anorectal abscesses and 1526 anorectal fistulas-in-ano. During these years I have become convinced of the importance of identifying the site of origin of the anorectal abscess because of the predictable process of spread of the suppuration if surgical intervention is delayed or if the patient is medically managed with antibiotics which permits the ab-
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Opening Subc. Ext.Sph.
Figure 3. Low intramuscular abscess ruptures through the medial terminal fibers of the longitudinal muscle into the perianal space, passing between the subcutaneous and super· ficial external sphincter muscles.
scess to involve other spaces. Appropriate surgical treatment of the abscess during the first 36 to 72 hours, when the pus is localized in one of the anorectal spaces, will prevent the formation of a fistula-inano in the vast majority of cases, minimizing the morbidity, decreasing the hospitalization, .and avoiding complications that may even result in death.20
Perianal Abscess-Fistula-in-Ano The majority of low intermuscular abscesses rupture through the longituainal muscle transsphincterically between the superficial and the subcutaneous external sphincter muscle into the perianal space (Fig. 3). This type of abscess is superficial, very painful, and located near the anal verge. It is readily recognizable by the red, inflamed skin with painful swelling and exquisite tenderness. In adults the swelling may extend more laterally and can be mistaken for an ischiorectal abscess. Perianal abscesses comprise 50 to 75 per cent of all anorectal abscesses and only approximately 35 to 40 per cent will not recur as a fistula after simple incision and drainage. 22 In considering all anorectal abscesses, Hughes 18 stated that 75 per cent of patients who have incision and drainage have further problems, and at St. Mark's, 196 abscesses were treated of which 151 recurred subsequently as fistulas. The pus of perianal abscess does not extend into the ischiorectal fossa but usually becomes fluctuant near the anal verge and frequently will rupture spontaneously if not treated. In infants, the perianal abscess is drained by a simple radial incision as an office procedure, or under light anesthesia, and the abscess seldom recurs as a fistula-in-ano. In adults with a large perianal abscess that is associated with an obvious primary opening in a crypt, the patient is hospitalized and definitive treatment by fistulotomy at
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Figure 4. Perianal abscess. A, If a probe cannot be passed through the primary opening, it may be passed retrograde through a stab incision. B, Fistulotomy and drainage of the abscess. (This procedure is contraindicated in anterior abscess in the female patient.) C, Alteration of anorectal anatomy after fistulotomy and drainage.
the time of incision and drainage is performed (Fig. 4). The abscess cavity and fistulous tract is curetted and a light fine mesh pack is placed in the wound for 24 hours.
Superficial Postanal Space Abscess This is a perianal space abscess and is managed in the same manner as just described (Fig. 4). Superficial Anterior Anal Space Abscess This type of perianal abscess in the male is treated in the same manner as described (Fig. 4); however, in female patients a simple incision and drainage is usually adequate. A "lay open" procedure is contraindicated. If an obvious primary opening is present, a staged procedure using a rubber band seton is advised (Fig. 5).
Deep Postanal Space Abscess The majority of anal glands are located in the posterior quadrant of the anorectum and their ducts enter into the anal crypts near the posterior Inidline or just to the left or right of the midline. The initial infection is a low intermuscular abscess that usually ruptures through the longitudinal muscle between the deep and superficial external sphincter muscles into the deep postanal space (Fig. SA). The abscess is located immediately posterior to the deep external sphincter. In rare instances, the pus may pass transsphincterically between the deep external sphincter and the puborectalis muscles. In the initial stage the abscess is localized in the deep postanal space. The patient has severe anorectal pain, fever, and leukocytosis. Inspection does not reveal any inflammatory skin changes because the abscess is deep. Digital rectal and bidigital exaInination causes exqui-
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Figure 5. A, Anterior superficial perianal space abscess in a female patient. B, Inset; Anteroposterior incision made over the abscess is extended posteriorly to the subcutaneous external sphincter. C, A rubber band is placed through the fistulous tract and loosely tied about the lower edge of the internal and subcutaneous external sphincter muscle.
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Figure 6. A, Deep postanal space abscess. B, Treatment (inset): Probe is placed in primary opening (a) into deep postanal abscess (g), incision over the probe will form fistulotomy of tract (e) and drains deep postanal abscess (g), separates superficial external sphincter into halves (f), and severs lower portion of internal sphincter (b), and longitudinal muscle (c), subcutaneous external sphincter (d) inferior surface of deep external sphincter preserved (h).
site pain and precludes evaluation of the deep postanal space. The abscess is inferior to the levator, superior to the superficial external sphincter muscle, and posterior to the deep external sphincter (Fig. 6A). After two to three days, the pus elevates the levator muscle and the abscess may be mistaken for a supralevator abscess on digital rectal examination. With such findings, the patient should be admitted to the hospital and examined under anesthesia to enable accurate anatomic evaluation. As surgical treatment of the ,acute deep postanal abscess, a probe is passed through the primary opening (Fig. 6B) in the posterior midline into the abscess cavity (g) in the direction of the coccyx. An incision is then made over the probe and a fistulotomy of the tract in the rectal wall (e) and drainage of the deep postanal space is accomplished (g). The incision severs the subcutaneous external sphincter (d), lower edge of the internal sphincter (b), and divides the superficial external sphincter into halves without severing its coccygeal attachment (f). Hospitalization averages three to five days and the wound is healed in five to six weeks. In our experience, the abscesses or fistulas have not recurred and incontinence l1 , 13 has not been a complication. If surgical treatment is delayed, the pus will spread into the ischiorectal fossa passing between the inferior surface of the levator muscle and the superficial external sphincter. Upon leaving the deep postanal space, the tract may divide into multiple tracts and extend anteriorly through the ischiorectal fossa along Colles' fascia to the perineum, scrotum, groin, and medial aspect of the thighs. In fulminating infection the scrotal skin may slough. These patients are treated by posterior midline fistulotomy and drainage of the deep postanal space,
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Figure 7. Treatment of advanced horseshoe abscess. A, Posterior midline fistulotomy incision and drainage of deep postanal space and drainage of fluctuant areas as illustrated. B, Ischiorectal fossa. e, Perineum and scrotum. D, Medial thigh.
and adequate drainage of the extension of the abscess over the ischiorectal fossae, perineum, and groin (Fig. 7).
Chronic Horseshoe Abscess-Fistula-in-Ano If a deep postanal space abscess has spread into the ischiorectal fossae and is simply drained or spontaneously ruptures, it will recur as a chronic horseshoe or semi-horseshoe fistula-in-ano. Chronic abscessfistula may become quiescent and recur as an acute abscess with the formation of a new tract and secondary opening (Fig. 8). Occasionally, the primary opening is sufficiently large to permit drainage into the rectum without the formation of a secondary opening (blind or incomplete fistula). Chronic fistulas are hard, fibrous inflammatory tubes varying in diameter from 3 to 7 mm. They are lined with infected granulation tissue. On digital and bidigital examination of the deep postanal space the tract can be palpated as a hard tube extending across the deep postanal space immediately posterior to the deep external sphincter muscle into one or both ischiorectal fossae. In subacute infection, the deep postanal abscess and the tracts are ill-defined. Some surgeons,3. 8,17-23 in treating chronic horseshoe fistula-in-ano, follow the basic principles advocated by John Arderne,2 that is, to incise ("lay open") the fistulous tracts in their entirety from all secondary openings to the primary opening in the rectum. I have used a more
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conservative surgical approach since 1963 with excellent resultsY' 13, 15 A probe is passed through the primary fistulous opening toward the coccyx (Fig. 6). An incision in the posterior midline over the probe accomplishes a fistulotomy of the portion of the tract going through the wall of the rectum. The incision separates the superficial external sphincter muscle into halves, severing the subcutaneous external sphincter and the lower edge of the internal sphincter. With the postanal space opened, the primary tract and its bifurcation in the deep postanal space are identified and can be seen to enter the ischiorectal fossae. In a chronic fistula the tract is like a hard tube and by sharp dissection the T-portion of the tract with the small length that extends under the superficial external sphincter muscle can be excised (Fig. 8). A circumferential incision is made about the secondary openings and the fistulous tracts may be completely cored out, including the portion that passes between the levator and the superficial external sphincter muscle to enter the deep postanal space. However, in most cases, fistulectomy is not necessary. The infection is more subacute, and these fistulas are treated by a posterior Inidline fistulotomy incision with enlargement of the secondary openings which perInits curettage of the entire tract and the chronic abscess in the postanal space (Fig. 8) with a sharp bone curette. In these cases no part of the tract needs to be excised. As the posterior midline fistulotomy wound heals, it will obliterate the communication between the deep postanal space and the ischiorectal fossae, resulting in the resolution of the distal inflammatory tracts. Fine mesh gauze is placed in the posterior wound and wick drain-
10 Opening
Figure 8. Chronic horseshoe fistula-in-ano with bilateral multiple secondary openings. Treatment: Posterior midline fistulotomy and surgical enlargement of secondary openings to permit curettage of tracts. In selected chronic cases complete fistulectomy including T portion of tract in deep postanal space may be done.
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age in the secondary openings. The drains are removed in 24 hours. While the patient is in the hospital, the fistulous tracts are swabbed with hydrogen peroxide solution. The postanal space is kept separated until the granulating surface has developed. The average stay in the hospital is six days. The wound heals in 5 to 12 weeks with a minimal defect of the anorectum without any incontinence.
Deep Anterior Anal Space Abscess-Fistula-in-Ano The anatomic alteration and pathogenesis are basically the same as those described for deep postanal space abscess and fistula. The intermuscular abscess ruptures the longitudinal muscle transsphincterically between the deep and superficial external sphincters into the deep anterior anal space. The symptoms are similar to those of a deep postanal space abscess - fever, severe anorectal pain, leucocytosis, with no cardinal signs of inflammation of the skin (Fig. 9A). The pus remains localized in the deep anterior space for two or three days and then may spread posteriorly to involve one or both ischiorectal fossae; anteriorly, it may spread to the right or left of the perineum to the labia; cephalad, into the rectovaginal septum, or lateral, to the vaginal vault, the abdominal wall, or the medial aspect of the thighs. At times the abscess may rupture into the lower part of the vagina causing rectovaginal fistula. This type of abscess, when seen early, requires examination under anesthesia to determine the anatomic alterations in order to determine the preferred surgical treatment. In the male patient, on rare occasions the pus may extend anteriorly superior to the triangular ligament between the bulbocavernosa and ischiocavernosa muscles. Deep anterior anal space abscess in men is treated by anterior fistulotomy and drainage of the deep anterior anal space as described for deep postanal space abscess (Fig. 6B). In females, a staged procedure will obtain the best functional results (Fig. 9). The rubber band acts as a drain and converts the deep complicated fistula into a simple fistula about the rubber band. The abscess cavity is curetted and packed with fine mesh gauze. The following day the pack is removed. In three to four weeks the infection is resolved, and only a simple fistula remains about the rubber band (Fig. IDA). The rubber band is tightened slightly at three weeks' intervals three or four times. This severs the sphincter in stages with a minimal separation, giving good functional results (Fig. lOB). Low chronic rectovaginal fistula resulting from a deep anterior anal space abscess may be treated with a transrectal exclusion procedure. 21 Epithelialized tracts should be excised by coring out.
Ischiorectal Abscess Primary abscess of the ischiorectal fossa is extremely rare because anal glands are located in the posterior or anterior quadrants of the anorectum. Ischiorectal abscess is usually a complication of a deep postanal space abscess, and occasionally deep anterior space or supralevator abscess. Therefore, when a clinical diagnosis of ischiorectal abscess is made, deep postanal and anterior anal space abscess must
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Figure 9. A, Deep anterior anal space abscess in a female patient. B, Abscess drained lateral to the perineum and vagina, incision 1. The probe passed through the primary opening and brought out through drainage incision 1. A stab incision (2) is made to the probe in the midline anterior to the subcutaneous external sphincter. The probe is withdrawn and reinserted through incision 2. A rubber band is secured to the probe, pulled through the tract, and loosely tied about the lower part of the internal sphincter and subcutaneous external sphincter (C).
be carefully ruled out to ensure proper surgical management. The treatment of ischiorectal abscess or a chronic fistula-in-ano is a simple "lay-open" fistulotomy procedure (Fig. 4).
High Intermuscular-Supralevator Abscess Approximately 5 per cent of intermuscular abscesses rupture into the supralevator spaces. If the intermuscular abscess extends above the level of the puborectalis and internal sphincter, the longitudinal muscle loses its lateral support and the abscess may rupture into one of the supralevator spaces or into the rectum through its thin circular muscle. The internal sphincter acts as a strong barrier and prevents low intermuscular abscesses from rupturing into the rectum below the anorectal ring. While supralevator spaces are described as separate entities, an abscess originating in one space may ultimately involve all of the spaces. The pus may completely surround the rectum, ascend re-
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troperitoneally to the diaphragm and/or to the anterior abdominal wall between the transversalis fascia and the peritoneum to rupture ultimately through the peritoneum below the semicircular valve of Douglas into the peritoneal cavity. Marks et al. 19 reported the fatal potential of fistula-in-ano with abscess. In chronic cases the lumen of the rectum may be constricted by the extrarectal inflammatory reaction. In contrast to acute infralevator abscess, pain is not a prominent symptom. However, the patient is acutely ill with high fever, chills, leukocytosis, urinary retention, adynamic ileus, and a vague, dull, aching fullness of the rectum. The abscess is located above the somatic sensory innervation; therefore, there is no acute rectal pain as observed in infralevator abscess. The initial clinical signs and symptoms are not anorectal and may be attributed to pneumonitis or acute urinary infection, delaying diagnosis. Digital rectal examination will reveal a large, boggy supralevator space abscess. On anoscopic examination a primary opening in or near the posterior or anterior midline crypt or in a chronic anal fissure may be found. Retrorectal Supralevator Abscess
Digital rectal examination within 48 to 72 hours after the onset of infection will reveal an elongated, tense intermuscular abscess extending from the intersphincteric line to above the anorectal ring. The mass may be 1.5 em wide to 4 to 5 em in length. If not treated in the early stages, the abscess ruptures the longitudinal muscle above the anorectal ring into the retrorectal space (Fig. llA). Chronic anal fissure (ulcer) may also cause high intermuscular abscess resulting in a
Figure 10. A, Deep anterior anal space abscess resolving several days after operation with a simple fistula forming around the rubber band. B, Appearance of wound three months after procedure.
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Figure 11. A, A high intermuscular abscess ruptures the longitudinal muscle above the level of the puborectalis to form a retrorectal abscess. B, Chronic anal fissure (ulcer) may also cause high intermuscular abscess resulting in a supralevator space abscess. C, A probe is passed through the primary opening into the retrorectal abscess. D, The alteration in anorectal anatomy after a complete internal sphincterotomy and drainage through the rectal wall.
supralevator space abscess (Fig. lIB). As a surgical treatment, a probe is passed through the primary opening, intermuscular abscess, into the retrorectal abscess (Fig. lIe). Internal sphincterotomy over the probe to the site of rupture of the longitudinal muscle is done (Fig. lID). The perforation is enlarged bluntly by spreading the tips of a Kelly forceps or a finger can be inserted into the cavity. Penrose drains are placed into the abscess cavity. The internal sphincterotomy disrupts the pathologic process of fistula formation and the supralevator infection resolves. If the supralevator abscess ruptures into the rectum, it may persist as a chronic anorectal fistula. The primary opening in the posterior midline may be seen during anoscopic examination. The tube-like intermuscular tract is palpable to the secondary opening in the rectum. Treatment is internal sphincterotomy over a probe passed through the
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primary opening, intermuscular tract, and out of the secondary opening in the rectum. High Intermuscular Rectovesical Supralevator Abscess Anterior intermuscular abscess ruptures into the rectovesical space. The treatment is illustrated in Figure 12. All supralevator spaces connect, and the pus will encircle the entire rectum if treatment is delayed. Patients with an extensive septic abscess may require additional drainage by making an anterior-posterior incision over the ischiorectal fossa and draining the pelvis through the levator muscles. Retroperitoneal drainage through a lateral flank incision may be necessary.
Figure 12. A. Early localized high intermuscular abscess, before it ruptures into rectovesical space (B). C, Treatment: Probe is passed through the primary opening into the rectovesical abscess. Internal sphincterotomy over the probe. D, The perforation of the longitudinal muscle is enlarged with a Kelly forceps or by placing a finger into the abscess. Penrose rubber drains are placed into the abscess cavity. Illustrations demonstrate alteration in anorectal anatomy after surgery.
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Supralevator Abcess
Levator Ani
Figure 13. Combined supralevator, retrorectal, and infralevator deep postanal space abscess.
Deep Post anal Abcess
Pelvic Rectal Supralevator Abscess Pelvic rectal space abscesses are usually the extension of pus from retrorectal or rectovesical spaces. Combined Supralevator and Infralevator Abscess Fistula-in-Ano On some occasions a large intermuscular abscess will drain into the supralevator retrorectal space and also trans sphincteric ally into one of the infralevator anorectal spaces. The treatment for a combined supralevator and infralevator abscess is dependent upon the spaces involved. The treatment for the type demonstrated in Figure 13 is internal sphincterotomy, as illustrated in Figure 11, and a posterior midline fistulotomy, as illustrated in Figure 6. Subcutaneous Anal Canal Abscess Subcutaneous anal canal abscesses result from infected subepithelial anal glands or chronic anal fissure. They usually rupture spontaneously or may be drained under local anesthesia in the office. They may recur as a short subcutaneous fistula that becomes asymptomatic. If symptomatic, a simple fistulotomy is required. Submucosal Rectal Abscess Intermuscular abscess or chronic fistula is frequently diagnosed as submucosal disease. However, submucosal rectal abscesses may be seen as a complication of inflammatory bowel disease. Surgical treatment is seldom necessary.
REFERENCES 1. Allingham, H. W.: Diagnosis and Treatment of Diseases of the Rectum. Edition 5. London, Churchill, 1888.
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2. Arderne, J.: Translated by Sir Darcy Power: Treatise of Fistula-in-ano and Hemorrhoids and Clysters. New York, Oxford, 1910. 3. Bacon, H. E.: Anus, Rectum, and Sigmoid Colon. Philadelphia, Lippincott, 1943. 4. Eisenhammer, A.: The internal anal sphincter: Its surgical importance. S. Afr. Med. J., 27 :266-270, 1953. 5. Eisenhammer, S.: Internal anal sphincter and anorectal abscess. Surg. Gynecol. Obstet., 103 :501-506, 1956. 6. Eisenhammer, S.: A new approach to anorectal fistulous abscess based on the high intermuscular lesion. Surg. Gynecol. Obstet., 106:595-599, 1958. 7. Eisenhammer, S.: The anorectal fistulous abscess and fistula. Dis. Colon Rectum, 9:91-106, 1966. ' 8. Gabriel, W. B.: The Principles and Practice of Rectal Surgery. Edition 4. Springfield, Charles C Thomas, 1948, p. 85. 9. Golligher, J. C.: Surgery of the Anus, Rectum and Colon. Springfield, Charles C Thomas, 1972. 10. Hanley, P. H., and Hines, M. 0.: Presacral epidermoid cyst. Am. Surg., 21 :898-908, 1955. 11. Hanley, P. H.: Conservative surgical correction of horseshoe abscess fistula. Dis. Colon Rectum, 8 :361-368, 1965. 12. Hanley, P. H.: Retrorectal tumors. In Turrell, R. (ed.): Diseases of the Colon and Rectum. Philadelphia, W. B. Saunders Co., 1969. 13. Hanley, P. H., Ray, J. E., Pennington, E. E., et al.: Horseshoe fistula in ano: Ten year follow-up. Dis. Colon Rectum, 19:507-515, 1976. 14. Hanley, P. H.: Rubber band seton in management of abscess anal fistula. Ann. Surg. April 1978. 15. Hanley, P. H.: Anorectum. In Hardy, J. D. (ed.): Rhoads Textbook of Surgery: Principles and Practice. Edition 5. Philadelphia, J. B. Lippincott Co., 1977, pp. 1259-1279. 16. Harkins, H. N.: Correlation of the newer knowledge of surgical anatomy of the anorectum. Dis. Colon Rectum, 8:154-157,1965. 17. Hughes, E. S. R.: Surgery of the Anus, Anal Canal, and Rectum. Edinburgh and London, Livingstone, Ltd., 1957. 18. Hughes, E. S. R.: Inflammation and infection of the anus. In Turrell, R. (ed.): Philadelphia, W. B. Saunders Co., 1959, Ch. 44. 19. Marks, G., Chase, W. V., and Mervin, T. B.: The fatal potential of fistula in ano with abscess. Analysis of eleven deaths. Dis. Colon Rectum, 16 :224-230, 1973. 20. Parks, A. G.: Pathogenesis and treatment of fistula-in-ano. Br. Med. J., 1 :463-469, 1961. 21. Russell, R. T., and Gallagher, D. M., Low rectovaginal fistulas: Approach and treatment. Am. J. Surg., 134:13-18,1977. 22. Scoma, J. A., Salvati, E. P., and Rubin, R. J.: Incidence of fistulas subsequent to anal abscesses. Dis. Colon Rectum, 17:357-359,1974. 23. Shackelford, R. T., and Dugan, H. J.: Surgery of the Alimentary Tract. Vol. 3. Philadelphia, W. B. Saunders Co., 1955. Ochsner Clinic 1514 Jefferson Highway New Orleans, Louisiana 70121
Anorectal Abscess Fistula
Patrick H. Hanley, M.D. *
Suppurative anorectal disease, such as abscess-fistula-in-ano, is an anatomic alteration and thus requires a thorough knowledge of the anatomy and structures surrounding the anorectum to enable early diagnosis and appropriate treatment.
ANATOMICAL BASIS The anorectum is 4 cm in length. The dentate or mucocutaneous line demarcates the junction of the lower rectum with the anal canal. Two cm proximal to the dentate line to the level of the anorectal ring (puborectalis muscle) is the lower rectum. Two cm distal to the dentate line to the anal verge is the anal canal. The anorectum is formed by the embryonic fusion of mesodermal, endodermal, and ectodermal tissues to form the intricate trilaminar arrangement of tissue planes that are of special pathological significance in suppurative diseases. The junction of the proctodeum with the blind pouch of the rectum forms the dentate line; however, the modified stratified squamous epithelium of the anal canal may override the columnar rectal mucosal epithelium, so that the dentate line does not sharply demarcate the epithelial junction. The pecten in, the upper third of the anal canal between the dentate line and the intersphincteric line is 3 to 7 mm in width. The subepithelial tissue space of the pecten is continuous with the submucosa of the lower rectum. It may contain anal glands which drain into the rectum through the anal crypts of Morgagni. The dentate line and the pecten area is the site of anastomosis of the hemorrhoidal circulation, the somatic and visceral lymphatics, and the cerebrospinal and sympathetic nerve supply of the anorectum. The blind pouch of the rectum descends anterior to the puborectalis and through the deep and superficial external sphincter. The cir"Emeritus Clinical Professor of Surgery, Tulane University School of Medicine, New Orleans; Senior Surgeon and Former Head, Department of Colon and Rectal Surgery, Ochsner Medical Institutions, New Orleans, Louisiana
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cular muscle of the lower rectum enlarges to form the internal sphincter which surrounds the upper two thirds of the anorectum and is a strong barrier that influences the direction of spread of intermuscular abscesses. It extends from the puborectalis to the intersphincteric line. The puborectalis portion of the levator has its origin from the pubic bones and forms a sling about the upper limits of the anorectum. It is an important landmark in the treatment of fistula-in-ano. Immediately below the puborectalis, the deep component of the external sphincter completely encircles the upper third of the internal sphincter. The superficial external sphincter has its origin from the posterior surface of the coccyx and, upon reaching the posterior anorectum, divides into halves to give the anorectum a strong lateral support. It converges anteriorly to insert in the central tendon of the perineum. The subcutaneous portion of the external sphincter muscle encircles the lower third of the anorectum. The longitudinal muscle of the rectum separates the internal sphincter from the external sphincters. It receives fibers from the puborectalis at the anorectal ring to form the fibroelastic conjoined longitudinal muscle. Some of its fibers insert into all external sphincter components. At the lower level of the internal sphincter, it divides into a medial portion that inserts into the anal skin at the intersphincteric line and a lateral portion that passes between the superficial and the subcutaneous external sphincter muscles and extends laterally to insert into the. tuberosity of the ischium separating the ischiorectal fossa from the perianal spaces.
CLASSIFICATION Eisenhammer,4-7 Parks,2° and Harkins,16 emphasized that infection of anal glands in the space between the internal sphincter and the longitudinal muscle of the rectum is, with few exceptions, the cause of anorectal abscess, and the consensus is that anorectal abscess and fistula-in-ano are stages of the same condition. Therefore, initially an anorectal abscess is located in a specific anorectal space. This concept supports a new classification for anorectal space abscess and fistulain-ano based on the precise anatomic site of origin of the initial anorectal infection and the pathway of spread if not treated as a surgical emergency (Table 1). With few exceptions, abscess of the anorectum begins in the intermuscular space between internal sphincter and longitudinal muscles of the rectum. If the pus remains below the level of the anorectal ring, it is a low intermuscular abscess (Fig. 1). If untreated, it will rupture transphincterically to involve one of the infralevator anorectal spaces. If the intermuscular abscess extends upward above the anorectal ring, it is classified as a high intermuscular abscess (Fig. 2), and if untreated, it will either rupture through the longitudinal muscles to involve the supralevator spaces or into the rectum. In rare instances, the intermuscular abscess may result in combinations of infralevator transsphincteric and supralevator abscess-fistula-in-ano. The anal glands are
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Table 1.
Classification of Anorectal Abscess and Fistula-in-Ano
I. Low Intermuscular Abscess A. Infralevator- Transsphincteric 1. Perianal space 2. Superficial postanal space 3. Superficial anterior anal space 4. Deep postanal space (horseshoe) 5. Deep anterior anal space (horseshoe) 6. Ischiorectal fossae II. High Intermuscular Abscess A. Supralevator 1. Retrorectal space 2. Rectovesical space 3. Pelvirectal space III. Intermuscular abscess with combined supralevator and infralevator abscess IV. Subcutaneous anal canal space V. Submucosal rectal space
located primarily in the posterior and anterior quadrants of the anorectum; therefore, intermuscular abscesses are rarely seen laterally. Some intermuscular abscesses originate from active chronic anal fissure. This article will discuss only anorectal abscess fistulas due to infected anal glands. However, in the differential diagnosis of any sinus opening about the anus, one must consider infected presacral epidermoid inclusion cysts,10, 12 infected sebaceous cysts, hidradenitis suppurativa, furunculosis, penetrating wounds, foreign bodies, traumatic injuries, Crohn's disease, ulcerative colitis, diverticulitis, Bartholin abscesses, and postoperative complications.
SYMPTOMS Symptoms of intermuscular abscess are, at the onset, a dull, aching pain in the rectum (increasing in severity rapidly as the anorectal spaces become involved), chills, and fever. Digital rectal examination during the first two or three days will reveal an exquisitely tender, elongated, tense swelling in the intermuscular space (Figs. 1 and 2). If the abscess is not drained early, the symptoms progressively get worse.
SURGICAL TREATMENT The consensus of surgeons is that there is no place for conservative medical treatment of anorectal abscesses; they are all surgical emergencies. The treatment of an early intramuscular space abscess is to insert a probe through the primary opening, passing it cephalad into the abscess cavity,. and then to do a complete internal sphincterotomy, over the probe, with the electrosurgical unit (coagulating cur-
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Ext. Sph.
Fig. 1
Ext. Sph.
Fig. 2 Figure 1. Low intramuscular abscess descends to the medial termination of the longitudinal muscle of the rectum. It is below the level of the puborectalis. Figure 2. High intramuscular abscess dissects cephaled extending above the level of the puborectalis muscle.
rent). The abscess will drain into the rectum. Occasionally, it may be necessary to continue the incision downward to sever the subcutaneous external sphincter for better drainage. Severing the subcutaneous external sphincter anteriorly is contraindicated in the female patient. Early treatment under anesthesia will prevent the possible development of supralevator or infralevator trans sphincteric involvement and formation of a fistula-in-ano. Between 1950 and 1976 at Ochsner Clinic, we treated 840 anorectal abscesses and 1526 anorectal fistulas-in-ano. During these years I have become convinced of the importance of identifying the site of origin of the anorectal abscess because of the predictable process of spread of the suppuration if surgical intervention is delayed or if the patient is medically managed with antibiotics which permits the ab-
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Opening Subc. Ext.Sph.
Figure 3. Low intramuscular abscess ruptures through the medial terminal fibers of the longitudinal muscle into the perianal space, passing between the subcutaneous and super· ficial external sphincter muscles.
scess to involve other spaces. Appropriate surgical treatment of the abscess during the first 36 to 72 hours, when the pus is localized in one of the anorectal spaces, will prevent the formation of a fistula-inano in the vast majority of cases, minimizing the morbidity, decreasing the hospitalization, .and avoiding complications that may even result in death.20
Perianal Abscess-Fistula-in-Ano The majority of low intermuscular abscesses rupture through the longituainal muscle transsphincterically between the superficial and the subcutaneous external sphincter muscle into the perianal space (Fig. 3). This type of abscess is superficial, very painful, and located near the anal verge. It is readily recognizable by the red, inflamed skin with painful swelling and exquisite tenderness. In adults the swelling may extend more laterally and can be mistaken for an ischiorectal abscess. Perianal abscesses comprise 50 to 75 per cent of all anorectal abscesses and only approximately 35 to 40 per cent will not recur as a fistula after simple incision and drainage. 22 In considering all anorectal abscesses, Hughes 18 stated that 75 per cent of patients who have incision and drainage have further problems, and at St. Mark's, 196 abscesses were treated of which 151 recurred subsequently as fistulas. The pus of perianal abscess does not extend into the ischiorectal fossa but usually becomes fluctuant near the anal verge and frequently will rupture spontaneously if not treated. In infants, the perianal abscess is drained by a simple radial incision as an office procedure, or under light anesthesia, and the abscess seldom recurs as a fistula-in-ano. In adults with a large perianal abscess that is associated with an obvious primary opening in a crypt, the patient is hospitalized and definitive treatment by fistulotomy at
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Figure 4. Perianal abscess. A, If a probe cannot be passed through the primary opening, it may be passed retrograde through a stab incision. B, Fistulotomy and drainage of the abscess. (This procedure is contraindicated in anterior abscess in the female patient.) C, Alteration of anorectal anatomy after fistulotomy and drainage.
the time of incision and drainage is performed (Fig. 4). The abscess cavity and fistulous tract is curetted and a light fine mesh pack is placed in the wound for 24 hours.
Superficial Postanal Space Abscess This is a perianal space abscess and is managed in the same manner as just described (Fig. 4). Superficial Anterior Anal Space Abscess This type of perianal abscess in the male is treated in the same manner as described (Fig. 4); however, in female patients a simple incision and drainage is usually adequate. A "lay open" procedure is contraindicated. If an obvious primary opening is present, a staged procedure using a rubber band seton is advised (Fig. 5).
Deep Postanal Space Abscess The majority of anal glands are located in the posterior quadrant of the anorectum and their ducts enter into the anal crypts near the posterior Inidline or just to the left or right of the midline. The initial infection is a low intermuscular abscess that usually ruptures through the longitudinal muscle between the deep and superficial external sphincter muscles into the deep postanal space (Fig. SA). The abscess is located immediately posterior to the deep external sphincter. In rare instances, the pus may pass transsphincterically between the deep external sphincter and the puborectalis muscles. In the initial stage the abscess is localized in the deep postanal space. The patient has severe anorectal pain, fever, and leukocytosis. Inspection does not reveal any inflammatory skin changes because the abscess is deep. Digital rectal and bidigital exaInination causes exqui-
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Figure 5. A, Anterior superficial perianal space abscess in a female patient. B, Inset; Anteroposterior incision made over the abscess is extended posteriorly to the subcutaneous external sphincter. C, A rubber band is placed through the fistulous tract and loosely tied about the lower edge of the internal and subcutaneous external sphincter muscle.
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Figure 6. A, Deep postanal space abscess. B, Treatment (inset): Probe is placed in primary opening (a) into deep postanal abscess (g), incision over the probe will form fistulotomy of tract (e) and drains deep postanal abscess (g), separates superficial external sphincter into halves (f), and severs lower portion of internal sphincter (b), and longitudinal muscle (c), subcutaneous external sphincter (d) inferior surface of deep external sphincter preserved (h).
site pain and precludes evaluation of the deep postanal space. The abscess is inferior to the levator, superior to the superficial external sphincter muscle, and posterior to the deep external sphincter (Fig. 6A). After two to three days, the pus elevates the levator muscle and the abscess may be mistaken for a supralevator abscess on digital rectal examination. With such findings, the patient should be admitted to the hospital and examined under anesthesia to enable accurate anatomic evaluation. As surgical treatment of the ,acute deep postanal abscess, a probe is passed through the primary opening (Fig. 6B) in the posterior midline into the abscess cavity (g) in the direction of the coccyx. An incision is then made over the probe and a fistulotomy of the tract in the rectal wall (e) and drainage of the deep postanal space is accomplished (g). The incision severs the subcutaneous external sphincter (d), lower edge of the internal sphincter (b), and divides the superficial external sphincter into halves without severing its coccygeal attachment (f). Hospitalization averages three to five days and the wound is healed in five to six weeks. In our experience, the abscesses or fistulas have not recurred and incontinence l1 , 13 has not been a complication. If surgical treatment is delayed, the pus will spread into the ischiorectal fossa passing between the inferior surface of the levator muscle and the superficial external sphincter. Upon leaving the deep postanal space, the tract may divide into multiple tracts and extend anteriorly through the ischiorectal fossa along Colles' fascia to the perineum, scrotum, groin, and medial aspect of the thighs. In fulminating infection the scrotal skin may slough. These patients are treated by posterior midline fistulotomy and drainage of the deep postanal space,
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Figure 7. Treatment of advanced horseshoe abscess. A, Posterior midline fistulotomy incision and drainage of deep postanal space and drainage of fluctuant areas as illustrated. B, Ischiorectal fossa. e, Perineum and scrotum. D, Medial thigh.
and adequate drainage of the extension of the abscess over the ischiorectal fossae, perineum, and groin (Fig. 7).
Chronic Horseshoe Abscess-Fistula-in-Ano If a deep postanal space abscess has spread into the ischiorectal fossae and is simply drained or spontaneously ruptures, it will recur as a chronic horseshoe or semi-horseshoe fistula-in-ano. Chronic abscessfistula may become quiescent and recur as an acute abscess with the formation of a new tract and secondary opening (Fig. 8). Occasionally, the primary opening is sufficiently large to permit drainage into the rectum without the formation of a secondary opening (blind or incomplete fistula). Chronic fistulas are hard, fibrous inflammatory tubes varying in diameter from 3 to 7 mm. They are lined with infected granulation tissue. On digital and bidigital examination of the deep postanal space the tract can be palpated as a hard tube extending across the deep postanal space immediately posterior to the deep external sphincter muscle into one or both ischiorectal fossae. In subacute infection, the deep postanal abscess and the tracts are ill-defined. Some surgeons,3. 8,17-23 in treating chronic horseshoe fistula-in-ano, follow the basic principles advocated by John Arderne,2 that is, to incise ("lay open") the fistulous tracts in their entirety from all secondary openings to the primary opening in the rectum. I have used a more
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conservative surgical approach since 1963 with excellent resultsY' 13, 15 A probe is passed through the primary fistulous opening toward the coccyx (Fig. 6). An incision in the posterior midline over the probe accomplishes a fistulotomy of the portion of the tract going through the wall of the rectum. The incision separates the superficial external sphincter muscle into halves, severing the subcutaneous external sphincter and the lower edge of the internal sphincter. With the postanal space opened, the primary tract and its bifurcation in the deep postanal space are identified and can be seen to enter the ischiorectal fossae. In a chronic fistula the tract is like a hard tube and by sharp dissection the T-portion of the tract with the small length that extends under the superficial external sphincter muscle can be excised (Fig. 8). A circumferential incision is made about the secondary openings and the fistulous tracts may be completely cored out, including the portion that passes between the levator and the superficial external sphincter muscle to enter the deep postanal space. However, in most cases, fistulectomy is not necessary. The infection is more subacute, and these fistulas are treated by a posterior Inidline fistulotomy incision with enlargement of the secondary openings which perInits curettage of the entire tract and the chronic abscess in the postanal space (Fig. 8) with a sharp bone curette. In these cases no part of the tract needs to be excised. As the posterior midline fistulotomy wound heals, it will obliterate the communication between the deep postanal space and the ischiorectal fossae, resulting in the resolution of the distal inflammatory tracts. Fine mesh gauze is placed in the posterior wound and wick drain-
10 Opening
Figure 8. Chronic horseshoe fistula-in-ano with bilateral multiple secondary openings. Treatment: Posterior midline fistulotomy and surgical enlargement of secondary openings to permit curettage of tracts. In selected chronic cases complete fistulectomy including T portion of tract in deep postanal space may be done.
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age in the secondary openings. The drains are removed in 24 hours. While the patient is in the hospital, the fistulous tracts are swabbed with hydrogen peroxide solution. The postanal space is kept separated until the granulating surface has developed. The average stay in the hospital is six days. The wound heals in 5 to 12 weeks with a minimal defect of the anorectum without any incontinence.
Deep Anterior Anal Space Abscess-Fistula-in-Ano The anatomic alteration and pathogenesis are basically the same as those described for deep postanal space abscess and fistula. The intermuscular abscess ruptures the longitudinal muscle transsphincterically between the deep and superficial external sphincters into the deep anterior anal space. The symptoms are similar to those of a deep postanal space abscess - fever, severe anorectal pain, leucocytosis, with no cardinal signs of inflammation of the skin (Fig. 9A). The pus remains localized in the deep anterior space for two or three days and then may spread posteriorly to involve one or both ischiorectal fossae; anteriorly, it may spread to the right or left of the perineum to the labia; cephalad, into the rectovaginal septum, or lateral, to the vaginal vault, the abdominal wall, or the medial aspect of the thighs. At times the abscess may rupture into the lower part of the vagina causing rectovaginal fistula. This type of abscess, when seen early, requires examination under anesthesia to determine the anatomic alterations in order to determine the preferred surgical treatment. In the male patient, on rare occasions the pus may extend anteriorly superior to the triangular ligament between the bulbocavernosa and ischiocavernosa muscles. Deep anterior anal space abscess in men is treated by anterior fistulotomy and drainage of the deep anterior anal space as described for deep postanal space abscess (Fig. 6B). In females, a staged procedure will obtain the best functional results (Fig. 9). The rubber band acts as a drain and converts the deep complicated fistula into a simple fistula about the rubber band. The abscess cavity is curetted and packed with fine mesh gauze. The following day the pack is removed. In three to four weeks the infection is resolved, and only a simple fistula remains about the rubber band (Fig. IDA). The rubber band is tightened slightly at three weeks' intervals three or four times. This severs the sphincter in stages with a minimal separation, giving good functional results (Fig. lOB). Low chronic rectovaginal fistula resulting from a deep anterior anal space abscess may be treated with a transrectal exclusion procedure. 21 Epithelialized tracts should be excised by coring out.
Ischiorectal Abscess Primary abscess of the ischiorectal fossa is extremely rare because anal glands are located in the posterior or anterior quadrants of the anorectum. Ischiorectal abscess is usually a complication of a deep postanal space abscess, and occasionally deep anterior space or supralevator abscess. Therefore, when a clinical diagnosis of ischiorectal abscess is made, deep postanal and anterior anal space abscess must
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Figure 9. A, Deep anterior anal space abscess in a female patient. B, Abscess drained lateral to the perineum and vagina, incision 1. The probe passed through the primary opening and brought out through drainage incision 1. A stab incision (2) is made to the probe in the midline anterior to the subcutaneous external sphincter. The probe is withdrawn and reinserted through incision 2. A rubber band is secured to the probe, pulled through the tract, and loosely tied about the lower part of the internal sphincter and subcutaneous external sphincter (C).
be carefully ruled out to ensure proper surgical management. The treatment of ischiorectal abscess or a chronic fistula-in-ano is a simple "lay-open" fistulotomy procedure (Fig. 4).
High Intermuscular-Supralevator Abscess Approximately 5 per cent of intermuscular abscesses rupture into the supralevator spaces. If the intermuscular abscess extends above the level of the puborectalis and internal sphincter, the longitudinal muscle loses its lateral support and the abscess may rupture into one of the supralevator spaces or into the rectum through its thin circular muscle. The internal sphincter acts as a strong barrier and prevents low intermuscular abscesses from rupturing into the rectum below the anorectal ring. While supralevator spaces are described as separate entities, an abscess originating in one space may ultimately involve all of the spaces. The pus may completely surround the rectum, ascend re-
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troperitoneally to the diaphragm and/or to the anterior abdominal wall between the transversalis fascia and the peritoneum to rupture ultimately through the peritoneum below the semicircular valve of Douglas into the peritoneal cavity. Marks et al. 19 reported the fatal potential of fistula-in-ano with abscess. In chronic cases the lumen of the rectum may be constricted by the extrarectal inflammatory reaction. In contrast to acute infralevator abscess, pain is not a prominent symptom. However, the patient is acutely ill with high fever, chills, leukocytosis, urinary retention, adynamic ileus, and a vague, dull, aching fullness of the rectum. The abscess is located above the somatic sensory innervation; therefore, there is no acute rectal pain as observed in infralevator abscess. The initial clinical signs and symptoms are not anorectal and may be attributed to pneumonitis or acute urinary infection, delaying diagnosis. Digital rectal examination will reveal a large, boggy supralevator space abscess. On anoscopic examination a primary opening in or near the posterior or anterior midline crypt or in a chronic anal fissure may be found. Retrorectal Supralevator Abscess
Digital rectal examination within 48 to 72 hours after the onset of infection will reveal an elongated, tense intermuscular abscess extending from the intersphincteric line to above the anorectal ring. The mass may be 1.5 em wide to 4 to 5 em in length. If not treated in the early stages, the abscess ruptures the longitudinal muscle above the anorectal ring into the retrorectal space (Fig. llA). Chronic anal fissure (ulcer) may also cause high intermuscular abscess resulting in a
Figure 10. A, Deep anterior anal space abscess resolving several days after operation with a simple fistula forming around the rubber band. B, Appearance of wound three months after procedure.
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Figure 11. A, A high intermuscular abscess ruptures the longitudinal muscle above the level of the puborectalis to form a retrorectal abscess. B, Chronic anal fissure (ulcer) may also cause high intermuscular abscess resulting in a supralevator space abscess. C, A probe is passed through the primary opening into the retrorectal abscess. D, The alteration in anorectal anatomy after a complete internal sphincterotomy and drainage through the rectal wall.
supralevator space abscess (Fig. lIB). As a surgical treatment, a probe is passed through the primary opening, intermuscular abscess, into the retrorectal abscess (Fig. lIe). Internal sphincterotomy over the probe to the site of rupture of the longitudinal muscle is done (Fig. lID). The perforation is enlarged bluntly by spreading the tips of a Kelly forceps or a finger can be inserted into the cavity. Penrose drains are placed into the abscess cavity. The internal sphincterotomy disrupts the pathologic process of fistula formation and the supralevator infection resolves. If the supralevator abscess ruptures into the rectum, it may persist as a chronic anorectal fistula. The primary opening in the posterior midline may be seen during anoscopic examination. The tube-like intermuscular tract is palpable to the secondary opening in the rectum. Treatment is internal sphincterotomy over a probe passed through the
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primary opening, intermuscular tract, and out of the secondary opening in the rectum. High Intermuscular Rectovesical Supralevator Abscess Anterior intermuscular abscess ruptures into the rectovesical space. The treatment is illustrated in Figure 12. All supralevator spaces connect, and the pus will encircle the entire rectum if treatment is delayed. Patients with an extensive septic abscess may require additional drainage by making an anterior-posterior incision over the ischiorectal fossa and draining the pelvis through the levator muscles. Retroperitoneal drainage through a lateral flank incision may be necessary.
Figure 12. A. Early localized high intermuscular abscess, before it ruptures into rectovesical space (B). C, Treatment: Probe is passed through the primary opening into the rectovesical abscess. Internal sphincterotomy over the probe. D, The perforation of the longitudinal muscle is enlarged with a Kelly forceps or by placing a finger into the abscess. Penrose rubber drains are placed into the abscess cavity. Illustrations demonstrate alteration in anorectal anatomy after surgery.
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Supralevator Abcess
Levator Ani
Figure 13. Combined supralevator, retrorectal, and infralevator deep postanal space abscess.
Deep Post anal Abcess
Pelvic Rectal Supralevator Abscess Pelvic rectal space abscesses are usually the extension of pus from retrorectal or rectovesical spaces. Combined Supralevator and Infralevator Abscess Fistula-in-Ano On some occasions a large intermuscular abscess will drain into the supralevator retrorectal space and also trans sphincteric ally into one of the infralevator anorectal spaces. The treatment for a combined supralevator and infralevator abscess is dependent upon the spaces involved. The treatment for the type demonstrated in Figure 13 is internal sphincterotomy, as illustrated in Figure 11, and a posterior midline fistulotomy, as illustrated in Figure 6. Subcutaneous Anal Canal Abscess Subcutaneous anal canal abscesses result from infected subepithelial anal glands or chronic anal fissure. They usually rupture spontaneously or may be drained under local anesthesia in the office. They may recur as a short subcutaneous fistula that becomes asymptomatic. If symptomatic, a simple fistulotomy is required. Submucosal Rectal Abscess Intermuscular abscess or chronic fistula is frequently diagnosed as submucosal disease. However, submucosal rectal abscesses may be seen as a complication of inflammatory bowel disease. Surgical treatment is seldom necessary.
REFERENCES 1. Allingham, H. W.: Diagnosis and Treatment of Diseases of the Rectum. Edition 5. London, Churchill, 1888.
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2. Arderne, J.: Translated by Sir Darcy Power: Treatise of Fistula-in-ano and Hemorrhoids and Clysters. New York, Oxford, 1910. 3. Bacon, H. E.: Anus, Rectum, and Sigmoid Colon. Philadelphia, Lippincott, 1943. 4. Eisenhammer, A.: The internal anal sphincter: Its surgical importance. S. Afr. Med. J., 27 :266-270, 1953. 5. Eisenhammer, S.: Internal anal sphincter and anorectal abscess. Surg. Gynecol. Obstet., 103 :501-506, 1956. 6. Eisenhammer, S.: A new approach to anorectal fistulous abscess based on the high intermuscular lesion. Surg. Gynecol. Obstet., 106:595-599, 1958. 7. Eisenhammer, S.: The anorectal fistulous abscess and fistula. Dis. Colon Rectum, 9:91-106, 1966. ' 8. Gabriel, W. B.: The Principles and Practice of Rectal Surgery. Edition 4. Springfield, Charles C Thomas, 1948, p. 85. 9. Golligher, J. C.: Surgery of the Anus, Rectum and Colon. Springfield, Charles C Thomas, 1972. 10. Hanley, P. H., and Hines, M. 0.: Presacral epidermoid cyst. Am. Surg., 21 :898-908, 1955. 11. Hanley, P. H.: Conservative surgical correction of horseshoe abscess fistula. Dis. Colon Rectum, 8 :361-368, 1965. 12. Hanley, P. H.: Retrorectal tumors. In Turrell, R. (ed.): Diseases of the Colon and Rectum. Philadelphia, W. B. Saunders Co., 1969. 13. Hanley, P. H., Ray, J. E., Pennington, E. E., et al.: Horseshoe fistula in ano: Ten year follow-up. Dis. Colon Rectum, 19:507-515, 1976. 14. Hanley, P. H.: Rubber band seton in management of abscess anal fistula. Ann. Surg. April 1978. 15. Hanley, P. H.: Anorectum. In Hardy, J. D. (ed.): Rhoads Textbook of Surgery: Principles and Practice. Edition 5. Philadelphia, J. B. Lippincott Co., 1977, pp. 1259-1279. 16. Harkins, H. N.: Correlation of the newer knowledge of surgical anatomy of the anorectum. Dis. Colon Rectum, 8:154-157,1965. 17. Hughes, E. S. R.: Surgery of the Anus, Anal Canal, and Rectum. Edinburgh and London, Livingstone, Ltd., 1957. 18. Hughes, E. S. R.: Inflammation and infection of the anus. In Turrell, R. (ed.): Philadelphia, W. B. Saunders Co., 1959, Ch. 44. 19. Marks, G., Chase, W. V., and Mervin, T. B.: The fatal potential of fistula in ano with abscess. Analysis of eleven deaths. Dis. Colon Rectum, 16 :224-230, 1973. 20. Parks, A. G.: Pathogenesis and treatment of fistula-in-ano. Br. Med. J., 1 :463-469, 1961. 21. Russell, R. T., and Gallagher, D. M., Low rectovaginal fistulas: Approach and treatment. Am. J. Surg., 134:13-18,1977. 22. Scoma, J. A., Salvati, E. P., and Rubin, R. J.: Incidence of fistulas subsequent to anal abscesses. Dis. Colon Rectum, 17:357-359,1974. 23. Shackelford, R. T., and Dugan, H. J.: Surgery of the Alimentary Tract. Vol. 3. Philadelphia, W. B. Saunders Co., 1955. Ochsner Clinic 1514 Jefferson Highway New Orleans, Louisiana 70121