A rectal biopsy is usually part of anoscopy or sigmoidoscopy. First, a digital rectal examination is performed. The doctor inserts a lubricated, gloved finger into the rectum to determine if anything will block the insertion of the anoscope. A lubricated anoscope (or sometimes a rectal speculum or proctoscope) is then inserted, which will cause some pressure. A biopsy can be taken through any of these scopes. The scope is a short tube with a light attached; it enlarges the rectum to allow the doctor to view the entire anal canal. Anesthetic is introduced through the anoscope, then biopsy forceps, a cytology brush, culture swab, or suction catheter is introduced through the anoscope to take a sample. Afterward, the scope is slowly removed.
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