The colonoscopy is indicated for patients with a history of constipation, diarrhea, persistent rectal bleeding, or lower abdominal pain when results from proctosigmoidoscopy and a barium enema test prove negative or inconclusive. After the application of lubricant to the patient's anus and the tip of the colonoscope, the examiner inserts the colonoscope anally and advances it through the large intestine. Specimens may be obtained with biopsy forceps or a cytology brush.
Blood vessels are visible beneath the intestinal mucosa, which glistens from mucous secretions.
The colonoscopy may reveal the site of lower GI bleeding, diverticula, polyps, stricture, tumor, or the site of suspected ulcerative colitis or Crohn's disease.