(Flexible Sigmoidoscopy, Proctosigmoidoscopy, Proctoscopy, Anoscopy)

Procedure Overview

What is a sigmoidoscopy?

A sigmoidoscopy is a diagnostic procedure that allows the physician to examine the lower one-third of the large intestine. Sigmoidoscopy is helpful in identifying the causes of diarrhea, abdominal pain, constipation, abnormal growths, and bleeding. It may also be used to obtain biopsies and to perform procedures such as removal of polyps or hemorrhoids. Sigmoidoscopy is also used to screen for colorectal cancer, the second leading cause of cancer deaths in the US.

A short, flexible, lighted tube, called a sigmoidoscope, is inserted into the intestine through the rectum into the lower part of the large intestine. Air is injected into the intestine through the sigmoidoscope to inflate it for better viewing.

Several procedures may be used to examine different portions of the large intestine. These include a colonoscopy (examination of the entire length of the large intestine), proctoscopy (examination of the anus and rectum), and anoscopy (examination of the anus only).

Although less invasive x-ray procedures, such as a barium enema, may be used to evaluate the large intestine, these procedures cannot provide the direct visualization of the internal intestine necessary to evaluate and diagnose certain conditions.

Other related procedures that may be used to diagnose problems of the large intestine include a barium enema and a colonoscopy. Please see these procedures for additional information.

Anatomy of the colon:

The large intestine, or colon, has four sections:

  • ascending colon - extends upward on the right side of the abdomen

  • transverse colon - extends from the ascending colon across the body to the left side

  • descending colon - extends from the transverse colon downward on the left side

  • sigmoid colon - named because of its S-shape; extends from the descending colon to the rectum

The rectum joins the anus, or the opening where waste matter passes out of the body.

Screening guidelines for colorectal cancer:

Colorectal cancer screening guidelines for early detection from the American Cancer Society recommend that beginning at age 50, both men and women should follow one of the examination schedules below:

  • annual fecal occult blood test (FOBT) or fecal immunochemical test (FIT) and flexible sigmoidoscopy (FSIG) every five years

  • FOBT or FIT every year

  • FSIG every five years

  • double-contrast barium enema every five years

  • colonoscopy every 10 years

Persons with any of the following colorectal cancer risk factors should begin screening procedures at an earlier age and be screened more often:

  • strong family history of colorectal cancer or adenomatous polyps in a first-degree relative, in a parent or sibling before the age of 60 or in two first-degree relatives of any age

  • family with hereditary colorectal cancer syndromes, such as familial adenomatous polyposis (FAP) and hereditary nonpolyposis colon cancer (HNPCC)

  • personal history of colorectal cancer or adenomatous polyps

  • personal history of chronic inflammatory bowel disease

Reasons for the Procedure

A sigmoidoscopy may be used to visualize or diagnose colon polyps, tumors, ulceration, inflammation, hemorrhoids, diverticula (pouches), and strictures (narrowing) in the sigmoid colon. It may also be used to determine the cause of recent changes in bowel habits, lower abdominal pain, itching around the anus, or the passage of blood or mucus in the stool.

There may be other reasons for your physician to recommend a sigmoidoscopy.

Risks of the Procedure

As with any invasive procedure, complications may occur. Complications related to sigmoidoscopy may include, but are not limited to, the following:

  • persistent bleeding after biopsy

  • peritonitis (inflammation of the lining of the abdominal cavity)

  • perforation of the intestinal wall (rare)

Did You Know?

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