Colonoscopy Frequently Asked Questions: What You Need to Know

If you're viewing this page, odds are your doctor has suggested that you have a procedure called a Colonoscopy, one of the screening procedures used in the early detection of colorectal cancer when it is most treatable. Current screening guidelines suggest that women and men at average risk for colorectal cancer should have a screening test for colorectal cancer beginning at age 50 (colorectal cancer is rarely found in people under the age of 50).

Several methods can be used for screening—talk to your doctor. However, the FAQ below addresses many of the common questions that people have about colonoscopy:

What is a colonoscopy?

Colonoscopy is a diagnostic procedure that allows the physician to examine the entire large intestine. The procedure can assist in identifying problems with the colon, such as early signs of cancer, inflamed tissue, ulcers, and bleeding. Colonoscopy is also used to screen for colorectal cancer, the second leading cause of cancer-related deaths in the US and the fourth most common cancer in men and women.

Why would a colonoscopy be necessary?

A colonoscopy may be used to examine colon polyps, tumors, ulceration, inflammation, diverticula (pouches), strictures (narrowing), and foreign objects within the colon. It may also be used to find the cause of unexplained chronic diarrhea or gastrointestinal bleeding or to evaluate the colon after cancer treatment.

Colonoscopy may ordered by a doctor when the results of a barium enema and/or sigmoidoscopy show a need for further examination of the colon. There may be other reasons for your doctor to recommend a colonoscopy; talk to yours.

What happens during a colonoscopy?

An endoscope—a long, flexible, lighted tube, also called a colonoscope—is inserted through the rectum into the colon. In addition to allowing visualization of the internal colon, the colonoscope allows the doctor to irrigate, suction, inject air, and access the bowel with surgical instruments. During a colonoscopy, your doctor may remove tissue and/or polyps for further examination and possibly treat any problems that are discovered.

Other related procedures that may be used to assess problems of the colon include abdominal x-ray, computed tomography (CT scan) of the abdomen, abdominal ultrasound, barium enema, and sigmoidoscopy. Please talk to your doctor for additional information.

What are the risks associated with Colonoscopy?

As with any invasive procedure, complications may occur during colonoscopy, including: 

  • Persistent bleeding after biopsy or polyp removal
  • Peritonitis (inflammation of the lining of the abdominal cavity)
  • Perforation of the intestinal wall (rare)
  • Nausea, vomiting, bloating, or rectal irritation caused by the bowel cleanse prep and/or procedure
  • Adverse reaction to the sedative or pain medication

There may be other risks depending upon your specific medical condition. Be sure to discuss any concerns with your doctor before the procedure.

What should I expect before, during and after the procedure?

Your physician will explain the procedure to you and offer you the opportunity to ask any and all questions that you might have about the procedure. The video below offers details that can help you understand what to expect before, during and after colonoscopy.

You can also get additional information by visiting our Health Library and searching "Colonoscopy." Here you'll find many helpful articles including, a colonoscopy animation; information on colonoscopy and men; information on who needs a colonoscopy and why and more.