home > diseases, conditions and tests a-z list > colonoscopy article

Colonoscopy

Take the Tummy Trouble Quiz Digestive Disease Myths Slideshow Pictures Heartburn? Foods to Eat, Foods to Avoid Slideshow

Medical Author:

Jay W. Marks, MD

Jay W. Marks, MD

Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

View Full Profile

Medical Editor:

Bhupinder Anand, MD

What is colonoscopy?

Colonoscopy is a procedure that enables an examiner (usually a gastroenterologist) to evaluate the inside of the colon (large intestine or large bowel). The colonoscope is a four foot long, flexible tube about the thickness of a finger with a camera and a source of light at its tip. The tip of the colonoscope is inserted into the anus and then is advanced slowly, under visual control, into the rectum and through the colon usually as far as the cecum, which is the first part of the colon.

Why is colonoscopy done?

Colonoscopy may be done for a variety of reasons. Most often it is done to investigate the cause of blood in the stool, abdominal pain, diarrhea, a change in bowel habit, or an abnormality found on colonic X-rays or a computerized tomographic (CT) scan. Individuals with previous history of polyps or colon cancer and certain individuals with a family history of some types of non-colonic cancers or colonic problems that may be associated with colon cancer (such as ulcerative colitis and colonic polyps) may be advised to have periodic colonoscopies because their risks are greater for polyps or colon cancer. How often should one undergo colonoscopy depends on the degree of the risks and the abnormalities found at previous colonoscopies. More recently, it has been recommended that even healthy people at normal risk for colon cancer should undergo colonoscopy at age 50 and every 10 years thereafter, for the purpose of removing colonic polyps before they become cancerous.

What bowel preparation is needed for colonoscopy?

If the procedure is to be complete and accurate, the colon must be completely cleaned, and there are several colonoscopy preparations . Patients are given detailed instructions about the cleansing preparation. In general, this consists of drinking a large volume of a special cleansing solution or several days of a clear liquid diet and laxatives or enemas prior to the examination. These instructions should be followed exactly as prescribed or the procedure may be unsatisfactory, and may have to be repeated, or a less accurate alternative test may be performed in its place.