A colonoscopy checks your large intestine, also called the colon, for abnormal growths or other problems. The test is done with a narrow, flexible tube that has a light and camera. The tube is put in through your rectum and into your colon. The test helps your doctor diagnose illnesses and make plans for treatment if needed.

Your doctor may recommend a colonoscopy:
  • To look for early signs of cancer in the colon and rectum. It may be part of a routine screening, which usually starts at age 50.
  • To look for causes of unexplained changes in bowel habits
  • To evaluate symptoms like abdominal pain, rectal bleeding, and weight loss
Your doctor can also remove polyps from your colon during a colonoscopy.


Detailed preparation instructions will be provided upon scheduling your colonoscopy. You need to be on a clear liquid diet for 1 to 3 days before the colonoscopy.

What to expect and why you need a colonoscopy

Sheryl Pfeil, MD, a gastroenterologist at Ohio State, explains colonoscopy, the routine screening test used to detect any issues within the colon. Much like a mammogram, the colonoscopy is an important screening tool that can help keep you in good health.
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