4.1 Functional Anatomy of the Anal Canal and Anorectal Spaces 

The anal canal begins where the terminal portion of the large bowel passes through the pelvic floor muscles, and it ends at the anal verge. It measures roughly 4 cm in length. The wall of the anal canal is formed by a continuation of the circular muscle of the rectal wall; the smooth muscle is thickened in this area to form the internal anal sphincter. This smooth-muscle sphincter is wrapped by skeletal muscle, the external anal sphincter. The top of the external anal sphincter is formed by the U-shaped puborectalis muscle, which loops around the anus, arising and inserting on the pubis. This is felt posteriorly and laterally as the anorectal ring on digital examination. The longitudinal muscle coat of the rectum descends in the plane between the sphincters as the conjoined longitudinal muscle, and it sends fibers across the lower part of the external anal sphincter to insert on the skin (corrugator cutis ani, responsible for the anocutaneous reflex or “anal wink”). These fibers also traverse the internal anal sphincter to insert on the submucosa (“mucosal suspensory ligament”).

In approximately the mid-anus there is a rolling line of demarcation called the dentate line. Above the line is columnar epithelium; below it is squamous epithelium without appendages (the anoderm). The demarcation does not really occur at a line, but at a transitional zone of 0.5–1 cm in length.

As the rectum narrows into the anal canal, the mucosa develops 6 to 14 longitudinal folds, Morgagni’s columns. Between the distal ends of the columns are small crypts. Anal glands open into the crypts. There are 4 to 10 glands, and they are lined by stratified columnar epithelium. About half of these tubular glands end in the intersphincteric plane.

Blood is supplied to the anus via the inferior rectal artery, a branch of the internal pudendal artery. The inferior rectal artery crosses the ischiorectal fossa. The superior rectal vein drains the upper part of the anal canal via the inferior mesenteric vein to the portal vein. The middle and inferior rectal veins drain the upper and lower anal canal into the systemic circulation via the internal iliac and internal pudendal veins, respectively.

Lymphatic drainage above the dentate line is via the superior rectal lymphatics (accompanying the superior rectal vessels) to the inferior mesenteric nodes, and laterally along the middle and inferior rectal vessels to the internal iliac nodes. Lymphatic drainage from the anal canal below the dentate line may be in a cephalad or lateral direction, but is primarily to the inguinal nodes.

Motor innervation of the external anal sphincter is via the inferior rectal branch of the pudendal nerve and the perineal branch of the fourth sacral nerve. The internal anal sphincter has sympathetic (motor) and parasympathetic (inhibitory) innervation. Parasympathetic supply is from the nervi erigentes (S2, S3, S4). Sympathetic innervation is from the first three lumbar segments via the preaortic plexus. Fibers from the preaortic plexus ultimately join the nervi erigentes to form the pelvic plexuses. Sensation below the dentate line (and for up to 1.5 cm above the dentate line) is carried by the inferior rectal nerve. Above the level of the inferior rectal nerve sensory distribution, there are only dull perceptions, mediated by parasympathetic fibers.

Around the anorectum are a number of potential spaces filled with fat or connective tissue. These may become the sites of abscess formation. The perianal space is at the anal verge, and is continuous with the intersphincteric space. The pyramid-shaped ischiorectal (ischioanal) fossa is medially bounded by the external anal sphincter and the levator ani muscles. The lateral wall is the obturator internus muscle and fascia. The inferior boundary is the skin of the perineum, and the apex is the origin of the levator ani from the obturator fascia. Posteriorly is the gluteus maximus muscle, and anteriorly the transverse perinei muscles. On the obturator fascia is Alcock’s canal, containing the internal pudendal vessels and pudendal nerve. The fossa is filled with fat and also contains the inferior rectal nerve and vessels, and the fourth sacral nerve. The two ischiorectal spaces communicate with one another behind the anal canal.

This section will review the symptoms associated with anorectal pathology and the techniques of anorectal examination.

As in most of medicine, taking a careful history is the most productive step in leading to a diagnosis. In the evaluation of the patient with anorectal complaints, there is a limited number of questions to be asked:

There are three common lesions that cause anorectal pain: fissure in ano, anal abscess and thrombosed external hemorrhoid. If the pain is sharp and occurs during, and for a short time following, bowel movements, a fissure is likely. Continuous pain associated with a perianal swelling probably stems from thrombosis of perianal vessels, especially when there is an antecedent history of straining, either at stool or with physical exertion. An anal abscess will also produce a continuous, often throbbing pain, which may be aggravated by the patient’s coughing or sneezing. Anorectal abscesses are generally associated with local signs of inflammation. The absence of an inflammatory mass in the setting of severe local pain and tenderness is typical of an intersphincteric abscess; the degree of tenderness usually prevents adequate examination, and evaluation under anesthesia is necessary to confirm the diagnosis and to drain the pus.

Anal pain of any etiology may be aggravated by bowel movements. Tenesmus, an uncomfortable desire to defecate, is frequently associated with inflammatory conditions of the anorectum. Although anal neoplasms rarely produce pain, invasion of the sphincter mechanism may also result in tenesmus. Tenesmus with urgency of evacuation suggests proctitis.

Transient, deep-seated pain that is unrelated to defecation may be due to levator spasm (“proctalgia fugax”).

Anorectal pain is so frequently, and erroneously, attributed to hemorrhoids, that this point bears special mention: pain is not a symptom of uncomplicated hemorrhoids. If a perianal vein of the inferior rectal plexus undergoes thrombosis, or ruptures, an acutely painful and tender subcutaneous lump will appear. This is the “thrombosed external hemorrhoid.” Internal hemorrhoids may prolapse and become strangulated to produce an acute problem of anorectal pain, tenderness, and mucous, bloody discharge. Gangrene and secondary infection may ensue.

The nature of the rectal bleeding will help determine the underlying cause. However, the clinician must remember that the historical features of the bleeding cannot be relied upon to define the problem with certainty. Bright red blood on the toilet paper or on the outside of the stool, or dripping into the bowl, suggests a local anal source, such as a fissure or internal hemorrhoids. Blood that is mixed in with the stool, or that is dark and clotted, suggests sources proximal to the anus. Melena is always due to more proximal pathology.

The associated symptoms are very helpful. A history of local anal bleeding, as described above, associated with painful defecation, suggests a fissure. The same bleeding pattern without pain suggests internal hemorrhoids; this may be associated with some degree of hemorrhoidal prolapse. Bleeding and diarrhea may occur with inflammatory bowel disease. When bleeding is associated with a painful lump and is not exclusively related to defecation, a thrombosed external hemorrhoid is likely. Bleeding associated with a mucopurulent discharge and tenesmus may be seen with proctitis, or possibly with a rectal neoplasm.

Bleeding per rectum is an important symptom of colorectal cancer, and although this is not the most common cause of hematochezia, it is the most serious and must always be considered. This does not mean that every patient who passes blood must have contrast radiography of the colon or total colonoscopy. If the bleeding has an obvious anal source, it may be prudent not to proceed with a total colon examination, especially in a patient at low risk for colorectal neoplasms (i.e., age under 50 years; no history of Crohn’s or ulcerative colitis; no family history of colon cancer; and no personal history of colorectal neoplasms). However, if bleeding persists after treatment of the anal pathology, more ominous lesions have to be excluded.

In evaluating protrusion from the anal opening, there are several relevant questions: Is the prolapse spontaneous or exclusively with defecation? Spontaneous prolapse is less characteristic of internal hemorrhoids than of hypertrophied anal papillae or complete rectal prolapse. Does the prolapsing tissue reduce spontaneously (as may be the case with second-degree internal hemorrhoids) or does it require manual reduction (as with third-degree internal hemorrhoids or complete rectal prolapse)? The patient may be able to describe the size of the prolapsing tissue, and this may suggest the diagnosis.

Complete rectal prolapse (procidentia) must be distinguished from mucosal prolapse or prolapsing internal hemorrhoids. Procidentia occurs mainly in women (female:male = 6:1), with a peak incidence in the seventh decade. Procidentia is often associated with fecal incontinence. In later stages, protrusion occurs even with slight exertion such as coughing or sneezing. The extruded rectum becomes excoriated, leading to tenesmus, mucus discharge and bleeding. (Examination of the patient with procidentia usually reveals poor anal tone, and with the tissue in a prolapsed state, the mucosal folds are seen to be concentric, whereas with prolapsed hemorrhoids there are radial folds.) Rarely, a large polypoid tumor of the rectum may prolapse through the anal canal.

A painful perianal lump may be an abscess or a thrombosed external hemorrhoid. Knowing whether there has been a discharge of blood or pus may be helpful. An intermittent mass suggests a prolapsing lesion.

External or “skin” tags are very common deformities of the anal margin. They may be the result of previous or active fissure disease, or the sequelae of a thrombosed external hemorrhoid. Condylomata acuminata – or venereal warts – are caused by a sexually transmitted virus. The perianal skin is frequently affected, and the condition occurs with greatest frequency in gay men.

The differential diagnosis also includes benign and malignant neoplasms.

Itching is a common associated feature of many anorectal conditions, especially during the healing phase or if there is a discharge. But pruritus ani may also be an isolated symptom or the patient’s primary complaint. As a chief complaint, pruritus may be caused by infections (e.g., pinworms, condylomata, Candida) or skin conditions (e.g., contact dermatitis, psoriasis). More commonly, no specific underlying pathology is identified, and the problem is idiopathic.

Idiopathic pruritus ani is more common in men, and is typically worse at night. When chronic, the characteristic changes of hypertrophy and lichenification, nodularity, scarring and fissuring of the skin become apparent.

Although mucus is a normal product of the colorectal mucosa, it is not normally seen in the stool. Increased mucus may be the result of proctocolitis or a colorectal neoplasm, especially a villous adenoma of the rectum. Both inflammatory and neoplastic conditions may present with mucus and blood. Phosphate enemas are irritating and often elicit copious mucus production. Patients with the irritable bowel syndrome may complain of mucous stools.

Mucus staining of the underclothes may be associated with prolapsing tissue. When the staining has a fecal component, or when there is associated inability to control gas or to discriminate gas from solids within the rectum, a disturbance of the continence mechanism exists. A history of “accidents,” or the need to wear pads during the day or night, will help indicate the magnitude of the problem. The discharge may arise from an obvious external lesion – e.g., blood from a thrombosed external hemorrhoid, or pus from an abscess, from the external opening of a fistula, from a pilonidal process or from perianal hidradenitis suppurativa.

Other issues that will prove helpful in coming to a diagnosis of anorectal pathology include bowel habits, associated medical conditions and medications, sexual practices, travel history and family history.

The patient about to undergo examination of the anorectum may not only be embarrassed, but also afraid of impending pain and discomfort. Explanation of the examinations to be performed, and reassurance, will lessen the patient’s anxiety and contribute greatly to patient cooperation.

The four steps in anorectal evaluation are inspection, palpation, anoscopy and proctosigmoidoscopy.

The patient is placed either in the left lateral position or (preferably) in the prone-jackknife position. The prone-jackknife position requires a special table that tilts the head down and raises the anorectal region, with the buttocks tending to fall apart. This provides the best and easiest access for the examiner, although patient comfort may be slightly less.

The left lateral (Sims’) position has the advantages of patient comfort and of being suitable for any examining table, bed or stretcher. The patient’s buttocks are allowed to protrude over the edge of the table, with hips flexed and knees slightly extended. The examiner may sit or stand.

The patient is unable to see “what’s going on back there,” and it is important to continually explain what you are doing and what can be expected.

Looking at the anal area may reveal obvious external pathology. The resting anal aperture should be observed: a patulous opening may be seen with procidentia, sphincter injury or neurologic abnormality. Straining and squeezing by the patient may provide information about anorectal function.

Gentle spreading of the buttocks may elicit pain in a patient who has an anal fissure. Asking the patient to strain down may provide information: internal hemorrhoids may protrude or procidentia may be seen. However, if procidentia is suspected, it should be sought with the patient squatting or sitting at the toilet.

A disposable plastic glove and water-soluble lubricant are required. The patient is told that a finger will be gently placed into the rectum. While one hand separates the buttocks, the index finger is placed on the anal verge, and with the patient bearing down, thereby relaxing the anus, the digit is advanced into the anal canal.

A methodical approach is best. Palpation anteriorly checks the prostate in males, and the cervix in females. The finger then sweeps backward and forward to palpate the rest of the circumference of the anorectum. This may be the only part of the examination that identifies submucosal lesions, which may easily go undetected by endoscopy. Resting tone and ability to squeeze should also be assessed. The location of tenderness or a palpable abnormality should be precisely recorded.

The anoscope is the optimal instrument for examining lesions of the anal canal. It is not a substitute for proctosigmoidoscopy, and the proctosigmoidoscope does not provide as satisfactory a view of the canal as does the anoscope. Many anoscopes are available; the best instrument is end-viewing, with an attached fiberoptic light source.

The rigid 25 cm sigmoidoscope (or proctoscope) is the best instrument for examining the rectum. A barium enema, because of the balloon-tipped catheter used in administering the contrast material, does not adequately evaluate the rectal ampulla and is never a sufficient workup of a lower GI complaint.

A variety of rigid sigmoidoscopes are available: disposable or reusable, in a range of diameters (1.1 cm, 1.9 cm, 2.7 cm) and with proximal or distal lighting. The 1.9 cm instrument provides good visibility with minimal patient discomfort. The instrument includes a 25 cm tube, a magnifying lens, a light source, and a bulb attachment for air insufflation. Long swabs may be helpful in maintaining visibility, but suction is best.

A single Fleet® enema provides excellent preparation of the distal bowel and should be used just before the examination. The Fleet® enema may produce transient mucosal changes, and if inflammatory bowel disease is suspected, it should be avoided.

The digital examination has set the stage for instrumentation by permitting the sphincter to relax. With the tip well lubricated, the sigmoidoscope is inserted and passed quickly up the rectum. As always, the patient is informed of what is being done, and is reassured that the sensation of impending evacuation is caused by the instrument, and that the bowels are not about to move.

Air insufflation should be kept to a minimum, as it may cause discomfort, but it is of value both on entry and on withdrawal in demonstrating the mucosa and lumen and in assessing rectal compliance and the presence of normal sensation of rectal distention. Advancement should occur only with the lumen clearly in sight. When the lumen is “lost,” withdraw and redirect to regain it.

As the rectosigmoid is reached (approximately 15 cm along), the patient should be warned of possible cramping discomfort that will disappear as the scope is removed. Frequently, even with experience, the rectosigmoid angle cannot be negotiated, and the examination should be terminated. Most importantly, the patient should not be hurt or caused significant discomfort. The scope should be withdrawn making large circular motions, carefully inspecting the circumference of the bowel wall, flattening the mucosal folds and valves of Houston. The posterior rectal wall in the sacral hollow must be specifically sought out, or it will be missed.

In most large studies, the average depth of insertion is 18–20 cm; the full length of the instrument is inserted in less than half the patients.

Perforation of the normal rectum by the sigmoidoscope is extremely rare (1 in 50,000 or less). However, advancing the instrument or insufflating air may be hazardous in settings such as inflammatory bowel disease, radiation proctitis, diverticulitis and cancer. Of course, biopsy and electrocoagulation have to be performed with care and with knowledge of the technique and equipment.

The incidence and significance of bacteremia following anorectal manipulations is controversial, and has been reported in 0–25% of proctoscopies. Prophylactic antibiotics should be considered in patients with prosthetic heart valves.

This section will briefly review some of the more common anorectal problems.

4.3.1.1 Background

The upper anal canal has three sites of thickened submucosa containing arterioles, venules and arteriovenous communications. These three vascular “cushions” are in the left lateral, right anterior and right posterior positions. Minor cushions may lie between the three main ones. The cushions are held in the upper anal canal by muscular fibers from the conjoined longitudinal muscle of the intersphincteric plane.

Hemorrhoids exist when the anal cushions prolapse after disruption of their suspensory mechanism, or when there is dilation of the veins and arteriovenous anastomoses within the cushions. Various theories can be put forward for the development of internal hemorrhoidal disease: raised intra-abdominal pressure, pressure on the hemorrhoidal veins by an enlarging uterus, poor venous drainage secondary to an overactive internal anal sphincter, straining at stool with a resultant downward displacement of the cushions, etc.

Skin tags are projections of skin at the anal verge. They may be the result of previous thrombosed external hemorrhoids, fissure in ano, or inflammatory bowel disease.

External hemorrhoids are dilated veins of the inferior hemorrhoidal (rectal) plexus. This plexus lies just below the dentate line and is covered by squamous epithelium.

Internal hemorrhoids are the symptomatic, enlarged submucosal vascular cushions of the anal canal. The cushions are located above the dentate line and are covered by columnar and transitional epithelium. The patient’s history allows internal hemorrhoids to be subdivided. First-degree hemorrhoids produce painless bleeding but do not protrude from the anal canal; at anoscopy, they are seen to bulge into the lumen. Second-degree hemorrhoids protrude with bowel movements, but reduce themselves spontaneously. Third-degree hemorrhoids prolapse outside the anal canal, either spontaneously or with bowel movements, but require digital reduction. Fourth-degree hemorrhoids are always prolapsed, and cannot be reduced.

4.3.1.2.1 Thrombosed external hemorrhoids

As a rule, external hemorrhoids are asymptomatic until the complication of thrombosis (intravascular clot) or rupture (perianal hematoma) supervenes. In either case, the presentation is severe pain with a perianal lump, often after straining. The natural history is one of continued pain for 4 to 5 days, then slow resolution over 10 to 14 days. The treatment depends on the severity of the pain and the timing of presentation. A patient who presents within 24 to 48 hours and with severe pain is best dealt with operatively. Under local anesthesia, the involved perianal vessel and clot are excised. The wound may be left open or may be closed. Simple evacuation of the thrombus is less effective. A patient presenting later, after 3 to 4 days, is advised to take frequent warm baths, a bulk laxative, a surface-active wetting agent, and oral analgesics. This regimen is also prescribed post-excision.

Painless, bright red rectal bleeding (usually with or following bowel movements) is the most common symptom of this condition. Blood appears on the toilet paper or on the outside of the stool, or drips into the bowl. It is very rare for the volume of blood lost from internal hemorrhoids to be sufficient to explain iron deficiency anemia; further workup is always indicated.

Prolapse with defecation or other straining activities is also a common symptom of internal hemorrhoids. Chronic prolapse is associated with mucus discharge, fecal staining of the underclothes and pruritus.

Anal sphincter spasm may result in thrombosis and strangulation of prolapsed hemorrhoids. This presents as an acute problem of a painful, discharging, edematous mass of hemorrhoids.

Inspection will identify the later stages of the disease, especially when the patient is asked to bear down. Digital examination can rule out other pathology, as well as assess the sphincters. A palpable abnormality suggests some other process. Anoscopy provides a diagnosis in first- and second-degree disease. With the anoscope in place, the patient is once again asked to strain, and the degree of prolapse observed. Proctosigmoidoscopy should always be performed to exclude other diseases, particularly rectal neoplasms and inflammatory bowel disease.

If the symptoms are at all atypical, or the physical findings leave any doubt about the source of blood, a colon-clearing examination (either colonoscopy or barium enema) should be performed.

In patients over the age of 50, it is reasonable to take the opportunity to screen (or to practice “case-finding”) for colorectal cancer by performing sigmoidoscopy with the 60 cm flexible instrument. If risk factors for colorectal neoplasia are present, then colonoscopy or barium enema should certainly be performed.

Occasional bleeding, especially if it is related to hard stools or straining, should be managed by improving bowel habits using high-fiber diet and bulk agents (e.g., psyllium). If bleeding persists or is frequent, intervention is indicated, and in most cases should take the form of rubber-band ligation. Prolapsing hemorrhoids that reduce spontaneously, or can be easily reduced, are also nicely treated by rubber-band ligation. If prolapsing tissue is not easily reduced, or if there is a significant external component, surgical hemorrhoidectomy offers the best cure. Similarly, prolapsed, thrombosed internal hemorrhoids should be surgically excised.

In this technique, strangulating rubber bands are placed at the cephalad aspect of the internal hemorrhoids. The absence of somatic pain fibers above the dentate line renders this a relatively painless procedure, as long as the rings are properly positioned. The banded tissue infarcts and sloughs over the next week, resulting in reduction of hemorrhoidal tissue, as well as fixation of the residual hemorrhoid in the upper anal canal. It is a simple office procedure requiring an anoscope and ligator. In general, only one or two areas are banded at a time, so that several treatments are often required. Long-term success is expected in approximately 75% of patients with second-degree hemorrhoids. Pain, bleeding and infection are rare complications.

Since the popularization of rubber-band ligation, excisional hemorrhoidectomy has been much less frequently performed. The important principles of all excisional procedures are removal of all external and internal hemorrhoids, protection of the internal anal sphincter from injury, and maintenance of the anoderm, so as to avoid anal stenosis.

This is a linear crack in the lining of the anal canal, extending from the dentate line to the anal verge. It is seen equally in men and women, and at all ages, but is a common entity in young adults. It is encountered mainly in the posterior midline, but also occasionally in the anterior midline. If a fissure persists, secondary changes occur. These include the “sentinel pile” at the distal end of the fissure and the “hypertrophied anal papilla” at the proximal end. They are due to edema and low-grade infection.

Fissure in ano is probably the result of trauma during the passage of hard stool, but not all patients with fissure in ano give a history of “constipation.” While most fissures will readily heal with an appropriate change in bowel habits, some will persist. This may be due to continued trauma or to spasm of the internal anal sphincter.

There is an association between fissures and inflammatory bowel disease, particularly Crohn’s disease, and this should be kept in mind.

Pain with defecation is the chief complaint. The pain may persist for minutes to hours. Bright red blood is often seen on the toilet paper and on the stool. The patient with an edematous, tender skin tag (sentinel pile) may complain of a painful hemorrhoid. The patient may be constipated in response to painful defecation.

With gentle separation of the buttocks, most fissures will be visible. The sentinel pile of a chronic fissure may be the initial finding. With acute fissures, digital and anoscopic examination are usually not possible because of local tenderness. However, these examinations should be performed later to rule out other pathology. With chronic fissures, anoscopy reveals the defect in the anoderm, with exposed muscle fibers of the internal anal sphincter at the fissure base. The hypertrophied anal papilla may be seen.

Fissures off the midline should raise the possibility of other diseases. Crohn’s disease may be associated with atypical-looking fissures that are off the midline and have atypical symptoms. Anal and rectal carcinoma should be palpably different from fissures, but if any doubt exists, a biopsy should be done. A syphilitic chancre may occasionally look like an idiopathic fissure.

The mainstay of therapy for acute fissures is to achieve daily soft bowel movements. This will prevent further tearing and relieve the anal spasm, allowing most acute fissures to heal within one to two weeks. Warm tub baths are soothing and cleansing, and may also reduce spasm. A high-fiber diet supplemented with bulk agents and surface-active wetting agents will accomplish the desired effect.

If the history is longer than a few weeks and the physical findings suggest chronicity (i.e., exposed sphincter fibers, hypertrophied papilla, sentinel pile and palpable induration), this conservative therapy may not help. If symptoms warrant, such a fissure should be treated operatively, generally by lateral internal sphincterotomy. This relieves the internal anal sphincter spasm and allows the fissure to heal in over 90% of cases. Minor disturbances of continence, especially for flatus, may complicate a sphincterotomy in 5–10% of patients.

Anorectal abscess and fistula are the acute and chronic phases, respectively, of the same disease. The disease begins as an infection in the anal glands and initially presents as an abscess. When the abscess is surgically drained, or drains spontaneously, a communication (i.e., a fistula) exists between the gland of origin and the perianal skin.

The infection begins in the intersphincteric plane, where many of the anal glands terminate. The infectious process may remain in this plane as an intersphincteric abscess, or, more commonly, it may track downward in the intersphincteric plane to present as a perianal abscess. Similarly, infection may penetrate the external sphincter to enter the ischiorectal fossa. Many complex variations are seen, determined by the direction of spread and sometimes by inappropriate intervention. The infection may track circumferentially from one side of the anal canal to the other to cause a “horseshoe” abscess. Perianal and ischiorectal abscesses account for at least three-quarters of anorectal abscesses.

The classical signs of inflammation are generally present, although with an intersphincteric abscess there may be nothing to see. In the case of intersphincteric abscess, the patient will be too tender for adequate examination, and examination under anesthesia will be necessary.

Management of the abscess consists of incision and drainage, and this can usually be accomplished under local anesthesia. To ensure adequate drainage, a cruciate or elliptical incision is made. For the one-half to two-thirds of patients who go on to develop a fistula in ano, a fistulotomy, or laying-open, with curettage of the track is required. The wound heals secondarily. Non-healing or recurrence of the fistula usually indicates a failure to destroy the gland of origin. In performing fistulotomy, the utmost attention must be paid to the anatomic relationship between the fistula track and the sphincter mechanism. Excessive division of muscle contained within the fistula can lead to partial or complete fecal incontinence.

This is an acquired condition in which body hair is drilled into the skin of the natal cleft by the back-and-forth motion of the buttocks. This produces a primary midline opening or track, from which abscesses and secondary tracks and openings may form.

The disease is mainly seen in young, hirsute males. It commonly presents as an acute abscess, but may also present as a chronic “sinus,” usually with multiple openings.

The abscess stage is treated by incision and drainage, usually under local anesthesia. After the abscess has healed, some of these patients will require definitive surgery to deal with the primary and secondary tracks. The preferred treatment consists of opening the anterior wall of the tracks and suturing the edge of the track to the skin edge. This technique is called “marsupialization.”

There is an increasing incidence of venereal infections of the anorectal region, mainly accounted for by sexual practices among gay men. Many of these diseases may mimic nonvenereal conditions of the anorectum, and multiple venereal infections may coexist.

While immunocompetent gay men are subject to infection with the usual venereal pathogens, AIDS patients may additionally suffer from opportunistic infections of the gut.

The common anorectal venereal infections seen in North America are discussed here.

Condylomata acuminata, or venereal warts, are seen in the perianal region and anal canal, as well as the vulva, vagina and penis. They are most often seen in male homosexuals. The causative agent is believed to be a papilloma virus with an incubation period of one to six months. Symptoms are generally minor – itching, and occasionally bleeding. Perianal warts are frequently accompanied by warts within the anal canal, and these must be looked for at anoscopy.

Many treatments exist. None has a better than 70% chance of eradicating the disease by a single application. For perianal and anal canal warts, electrocoagulation or laser destruction is preferred. For extensive persistent disease, immunotherapy with an autologous vaccine has been very successful.

Squamous cancer has been seen to arise in condylomata acuminata.

Neisseria gonorrhoeae may produce proctitis. The incubation period of gonococcal proctitis is five to seven days. Gonococcal proctitis is most often asymptomatic; symptoms may include mucopurulent discharge and tenesmus. Proctoscopy reveals a thick, purulent discharge on a background of mild, nonulcerative inflammation of the distal rectum. Gram’s stain is unreliable, but culture of the pus confirms the diagnosis. Serologic testing for syphilis should be carried out. Treatment for homosexual men is ceftriaxone, 250 mg IM once.

Syphilis can affect the anal region. The incubation period ranges from 9 to 90 days. The primary lesion is a chancre, and because it is painful, it may be mistaken for a fissure. However, chancres are off the midline, are often multiple, and have an atypical appearance. Bilateral inguinal lymphadenopathy may be present. The chancre regresses over 6 weeks. Treponema pallidum is demonstrated from the primary lesion by darkfield microscopy. Serologic testing will be positive within a few weeks of the appearance of the chancre. If untreated, the secondary stage of syphilis may involve the anal area 6 to 8 weeks after healing of the chancre. This takes the form of a rash or of condylomata lata – flat, wart-like lesions teeming with Treponema pallidum. Treatment of primary and secondary syphilis is with benzathine penicillin G, 2.4 million units IM once. Sexual contacts should be treated prophylactically.

Herpes simplex 2 may infect the anorectum. The incubation period is 4 to 21 days. Constitutional symptoms are followed by severe anorectal pain. Small vesicles and aphthous ulcers are seen perianally and in the anal canal and lower rectum. Examination may reveal tender inguinal lymphadenopathy. Viral cultures of the vesicular fluid will be positive and rectal biopsy has a characteristic appearance. Spontaneous resolution occurs over several weeks. Recurrences are frequent but less severe. Immunosuppressed patients may develop a severe, destructive process. Treatment is with tub baths and analgesics. Topical acyclovir q8h x 5 days shortens the symptomatic period and the duration of viral shedding. Intravenous acyclovir is used when there is proctitis in addition to anal and perianal disease. In the AIDS patient, acyclovir is used intravenously in the acute phase, followed by oral acyclovir for 6 months.

Chlamydia proctitis with non-LGV (lymphogranuloma venereum) serotypes is almost identical to gonococcal proctitis. However, the LGV serotypes are invasive and produce a severe proctocolitis with pain, tenesmus, discharge and diarrhea. Chlamydia is isolated from the rectum. Treatment is with tetracycline.