A rectal biopsy is a procedure to remove a small piece of rectal tissue for examination.

A rectal biopsy is usually part of anoscopy or sigmoidoscopy.

A digital rectal exam is done first. Then, a lubricated instrument (anoscope or proctoscope) is placed into the rectum. You will feel some discomfort when this is done.

A biopsy can be taken through any of these instruments.

You may get a laxative, enema, or other preparation before the biopsy so that you can completely empty your bowels.

There will be some discomfort during the procedure, and you may feel an urge to have a bowel movement. Cramping sometimes occurs as the instrument is placed into the rectal area.

A rectal biopsy is used to determine the cause of abnormal growths found during 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. When biopsy tissue is examined under a microscope, no abnormalities should be noted.

This test is one of the more common ways to confirm amyloidosis. It also determines the specific causes of abnormal conditions of the rectum, such as colitis. Other findings could include:

• Abscesses
• Colorectal polyps
• Hemorrhoids
• Infection
• Inflammation
• Tumors

The test may be also performed for:

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

There is some risk of bleeding and tearing. Occasionally, patients have problems with urinary retention and an inability to urinate after rectal biopsy.