Sigmoidoscopy Overview: Uses, Procedure, Risks

A sigmoidoscopy is a way for a doctor to examine the last one third of the large intestine, which includes the rectum and sigmoid colon. A flexible viewing tube with a lens and light source on the end, called a sigmoidoscope, is inserted through the anus and into the rectum. Looking through the eyepiece at the other end of the scope, the doctor can see the inside of the colon.

In this test, the doctor can check for cancer, abnormal growths (polyps) and ulcers. Most of the time, a sigmoidoscopy is done in a doctor's office, usually a gastroenterologist or a colorectal surgeon. There may or may not be a preparation, depending on the preference of the doctor and the reason for the test. It can be uncomfortable because there is no sedation, but most physicians keep the test very quick in order to cut down on patient discomfort. If there is a prep and sedation is used, the test might take longer.

Beginning at age 50, a sigmoidoscopy may be recommended every 3 to 5 years to screen for colorectal cancer. In people who are at a higher risk for colorectal cancer due to inflammatory bowel disease (IBD), especially ulcerative colitis, family history of colorectal cancer, or familial polyposis, screening may be recommended starting at age 35.

A sigmoidoscopy may also be used as a follow-up procedure after a digital rectal exam is abnormal, or after a positive fecal occult blood test. It can also help identify the source of some types of rectal bleeding or other problems in the lower digestive tract. A biopsy may be taken during the procedure, if the doctor deems it necessary. If an abnormality is found in a sigmoidoscopy, a colonoscopy may be recommended.

In order for the doctor to get a clear view of the intestinal wall, the colon must be fairly empty. The doctor will give you specific instructions on how to prepare for the test, which may include laxatives or enemas. On the day of the test, your diet should consist mainly of liquids, rather than solid food.

You may be asked to wear a hospital gown or to remove your clothes from the waist down. An assistant may record temperature, pulse, blood pressure, and respiratory rate. You will be instructed to lie on your left side on the exam table, with one or both knees raised to your chest. The doctor will insert the sigmoidoscope into your rectum and pump air through the sigmoidoscope if necessary for a clearer view. A biopsy may be taken using a device on the end of the sigmoidoscope. A biopsy is a piece of tissue that can be sent to a lab for further analysis under a microscope.

Injury to the bowel is a rare complication of this procedure. The risks are so low that they're not worth postponing or canceling the test.

If a biopsy was taken, your doctor should have the results in a few days. A normal diet and schedule can be resumed immediately after the test.

Call your doctor immediately if you experience:

• Rectal bleeding
• Feeling faint
• Short of breath
• Palpitations

Call your doctor if you experience:

• nausea
• vomiting
• cramps
• abdominal pain
• fever
• chills
• severe headache
• muscle aches

A Word From Verywell

A sigmoidoscopy is limited to screening only the lower one third of the bowel. For a complete screening for colorectal cancer, a colonoscope is necessary to screen for cancer or polyps higher in the bowel.