Anorectal disorders result from a variety of causes, including infection, structural abnormalities, or systemic disorders. Anoscopy is used to evaluate patients with rectal bleeding, those with perianal or anal complaints, sexual assault victims, and 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 (Fig. 47-1). 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 epithelium thickens and hair follicles and cutaneous appendages appear.
Proximal to the dentate line, the mucosa has 8–14 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. 2 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).
No bowel prep is needed for anoscopic exam. Digital exam should always precede anoscopic exam to assess whether the patient will tolerate passage of the anoscope. 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 the hemorrhoids. Bleeding occasionally occurs after biopsy, and infection is rare.
An Ives slotted anoscope provides the best unobstructed view of the walls of the anal canal. A slotted instrument does not compress mucosa, so small 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 compressed mucosa through the instrument, but they have a smaller working opening, and their use can result in failure to visualize small lesions.
Indications⬆⬇
Initial evaluation of rectal bleeding
Anal or perianal pain
Pruritus ani
Anal discharge
Rectal prolapse
External or internal hemorrhoids
Anal fissures or fistulas
Perianal condyloma
Palpable masses or excessive pain on digital exam
HIV-positive patients with high serum HIV load, history of anal dysplasia, or condylomas
Contraindications⬆⬇
Uncooperative patient
Severe debilitation
Acute myocardial infarction
Acute abdomen (relative contraindication)
Marked anal canal stenosis
Procedure⬆⬇
Place the patient in the left lateral decubitus position with the left side down on the table and 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.
Visually inspect the external anus. Look for a sentinel skin tag in the posterior or anterior midline that that would indicate presence of a fissure.
Start the digital anorectal exam by informing the patient that you will touch the anus. With a gloved finger well lubricated with water-soluble lubricant or 2% lidocaine jelly, apply gentle pressure to the anal verge so that 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 tightening of external sphincter. Sweep the examining finger around the entire distal rectum.
With the obturator in place, lubricate the anoscope with water-soluble lubricant or 2% lidocaine jelly. Ask the patient to take a few gentle deep breaths. Insert anoscope very gently into he anal aperture, gradually overcoming the resistance of the sphincters. Gently advance the instrument until the full length of the anoscope is inserted (Fig. 47-1).
Pitfall: Patients can be placed in the knee-chest position, but this is more uncomfortable for the patient to maintain.
Remove the obturator to examine the mucosa (Fig. 47-2). Observe the appearance of the epithelium, dentate line, and mucosal vasculature, and look for any abnormal findings—e.g., blood, mucus, pus, or hemorrhoids.
Gradually withdraw anoscope, observing 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 3–4 mm of tissue is needed. Control any bleeding with pressure, Monsel's solution, or both.
Pitfall: If fecal matter is encountered, remove it with a large cotton swab.