Anorectal disorders result from a variety of causes, including infection, structural abnormalities, or systemic disorders. Anoscopy, a common procedure used to diagnose these conditions, is performed in ambulatory and emergency department settings. It is used to evaluate patients with rectal bleeding, those with perianal or anal complaints, sexual assault victims, and human immunodeficiency virus (HIV)-positive patients. It is also commonly performed in association with colonoscopy or flexible sigmoidoscopy.
The anorectum is the anatomic structure in which the endodermal intestine unites with the ectodermal anal canal and skin (see Figure 1). The dentate line (or pectinate line) marks the junction of these structures. The mucosa of the anal canal consists of stratified squamous epithelium without hair follicles or sweat glands. The most distal part of the anal canal (at the external opening) is the anal verge, where the epithelium thickens and hair follicles and cutaneous appendages appear. Proximal to the dentate line, the mucosa has 8 to 14 convoluted, longitudinal folds called the columns of Morgagni, with their associated crypts. At the base of some of these crypts is a small anal gland that secretes mucus to lubricate the anal canal. Two sleeves of circular muscles, the internal and external sphincters, surround the distal rectum and anal canal. Infection of these crypts and glands may result in cryptitis, fissures, abscesses, and fistulas (i.e., anal sepsis).
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(1) The anatomy of the anal canal. |
No bowel preparation is needed for an anoscopic examination. A digital examination should always precede an anoscopic examination to assess whether the patient will tolerate passage of an anoscope. The presence of an assistant is often helpful. A gloved assistant can separate the buttocks to allow better access and visibility of the perianal area. Inspection alone can reveal the presence of some fissures, fistulas, perianal dermatitis, masses, thrombosed external hemorrhoids, condyloma, and other growths.
Patients may perceive anoscopy as extremely embarrassing and uncomfortable. Objectively and honestly discuss the procedure with the patient while obtaining consent. Anoscopy generally has few complications; possibilities include minor lacerations, abrasions, or tearing of hemorrhoids. Bleeding occasionally occurs after biopsy, and infection is rare.
The Ives slotted anoscope provides the best unobstructed view of the walls of the anal canal. The slotted instrument does not compress the mucosa, so small
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lesions and hemorrhoids are more easily seen and treated. Because of its larger opening, it is the preferred instrument for treating hemorrhoids. The anoscope and obturator can be autoclaved. Disposable plastic anoscopes allow visualization of the compressed mucosa through the instrument, but they have a smaller working opening, and their use can result in failure to visualize small lesions.
INDICATIONS
CONTRAINDICATIONS
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PROCEDURE
The anatomy of the anal canal is demonstrated.
Place the patient in the left lateral decubitus position with the left side down on the table and the head toward the left as the examiner faces the patient. Slightly flex the patient's hips and knees, and draw the buttocks slightly off the edge of the table toward the examiner.
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(2) Place the patient in the left lateral decubitus position with the left side down on the table and the head toward the left as the examiner faces the patient. |
PITFALL: Patients can be placed in a knee-chest position, but this is more uncomfortable for the patient to maintain.
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Visually inspect the external anus. Look for inflammation or other dermatologic conditions. Gently everting the buttocks usually everts the anus enough to visualize anal skin tags, perianal abscesses, thrombosed external hemorrhoids, and anal fissures. Look for a sentinel skin tag in the posterior or anterior midline that that would indicate the presence of a fissure.
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(3) Visually inspect the external anus. |
Start a digital anorectal examination by informing the patient that you will touch the anus. With a gloved finger well lubricated with a water-soluble lubricant or 2% lidocaine jelly, apply gentle pressure to the anal verge so that the examining finger enters the anal canal. Anal fissures manifest as palpable defects or indurations, usually in the posterior midline. Assess the prostate gland in male patients. Assess anal sphincter function by asking the patient to “squeeze down” as if to try to stop a bowel movement and by feeling for the tightening of the external sphincter. Sweep the examining finger around the entire distal rectum.
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(4) Perform a digital anorectal examination. |
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An Ives slotted anoscope is used with the obturator in place for insertion into the anal canal (Figure 5A) and withdrawn for viewing (Figure 5B).
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(5) Ives slotted anoscope. |
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With the obturator in place, lubricate the anoscope with a water-soluble lubricant or 2% lidocaine jelly. Ask the patient to gently take a few deep breaths. Insert the anoscope very gently into the anal aperture, gradually overcoming the resistance of the sphincters. Gently advance the instrument until the full length of the anoscope is inserted.
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(6) With the obturator in place, lubricate the anoscope with a water-soluble lubricant, have the patient take a few deep breaths, and insert the anoscope very gently into the anal aperture. |
Remove the obturator to examine the mucosa. Observe the appearance of the epithelium, the dentate line, the mucosal vasculature, and for any abnormal findings such as blood, mucus, pus, or hemorrhoids. Gradually withdraw the anoscope, observing the anal canal as it is extracted. Then rotate the anoscope 120 degrees, and repeat the process. Repeat the procedure until the entire circumference of the anal canal is examined. A variety of long-handled biopsy instruments can be used to take a biopsy specimen. Keep the biopsy superficial; only 3 or 4 mm of tissue are needed. Control any bleeding with pressure or Monsel's solution, or both.
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(7) Remove the obturator to examine the mucosa. |
PITFALL: If fecal matter is encountered, remove it with a large cotton swab.
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CODING INFORMATION
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INSTRUMENT AND MATERIALS ORDERING
The Ives slotted anoscope ($160) is available from Redfield Corporation, 336 West Passaic Street, Rochelle Park, NJ (phone: 800-678-4472;http://www.redfieldcorp.com). A suggested anesthesia tray that can be used for this procedure is described in Appendix G.
BIBLIOGRAPHY
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