A rectal biopsy is a procedure in which a small piece of rectal (anal) tissue is removed for diagnostic examination.

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.

You will need to defecate before the procedure and a laxative, enema, or other preparation may be administered.

There will be some pressure during the procedure, and you may feel an urge to defecate. A small amount of cramping sometimes occurs as the anoscope is inserted, but there should be little pain.

A rectal biopsy is used to determine the cause of abnormal growths found on anoscopy, sigmoidoscopy, or other tests. It can also be used to confirm the diagnosis of amyloidosis.

The anus and rectum appear normal in size, color, and shape. There should be no evidence of bleeding, polyps, hemorrhoids, or other abnormalities. On microscopic examination of biopsy tissue, no abnormalities should be noted.

This test is one of the more common means to confirm amyloidosis. It also determines the specific causes of abnormal conditions of the rectum, such as colitis. Other findings could include colorectal polyps, abscesses, inflammation, infection, hemorrhoids, or tumors.

Additional conditions under which the test may be performed include the following:

• Hirschsprung's disease
• Ulcerative colitis
• Crohn's disease

There is some risk of bleeding, pain, and perforation. Occasionally, patients have problems with urinary retention after rectal biopsy.