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Anoscopy, Sigmoidoscopy, and Colonoscopy
Clinicians can now examine the anal canal, rectum, and colon with ease and with little discomfort to the patient. The indications for each procedure depend on the clinical presentation. For example, red blood on toilet paper or blood dripping into the toilet bowl frequently requires anoscopy and sigmoidoscopy but not colonoscopy. Chronic diarrhea or abdominal pain and signs of intermittent obstruction necessitate colonoscopy ( Fig. 79.1 ).
Anoscopic, Sigmoidoscopic, and Colonoscopic Views of Normal Intestinal Structures and Various Lesions.
Use of these techniques for cancer prevention and screening varies throughout the world. Most gastroenterologists agree that colonoscopy is the preferred procedure, whereas occult blood testing and sigmoidoscopy are practiced in many countries as part of colon cancer prevention programs. However, after risk factors (e.g., family history of colon cancer) are identified, colonoscopy is recommended.
Anoscopy
Anatomy and abnormalities of the anal canal are examined through anoscopy. The anoscope is a rigid instrument that may be short (proctoscope) or as long as 10 cm (anoscope). Examination requires little preparation, with the patient in the left lateral decubitus position and the buttocks spread by the examiner's left hand. The instrument is gently inserted into the rectum after digital examination. If digital examination is too difficult to perform because of the patient's marked obesity or severe pain, the procedure may have to be limited and deferred to a time when the patient can be sedated and full sigmoidoscopy or colonoscopy performed. After the anoscope or proctoscope is inserted, the anal ring and distal rectum can be carefully inspected. It may be necessary to place the patient in the knee-chest position to spread the buttocks wide. This is especially true with some obese patients, who may feel discomfort in the rectum.
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