Colonoscopy is a procedure used to see inside the colon and rectum. Colonoscopy can detect inflamed tissue, ulcers, and abnormal growths. The procedure is used to look for early signs of colorectal cancer and can help doctors diagnose unexplained changes in bowel habits, abdominal pain, bleeding from the anus, and weight loss.

Colonoscopy is performed by inserting a device called a colonoscope into the anus and advanced through the entire colon. The procedure generally takes between 20 minutes and one hour.


Reasons For Colonoscopy

The most common reasons for colonoscopy are to evaluate the following:

  • As a screening exam for colon cancer
  • Rectal bleeding
  • A change in bowel habits, like persistent diarrhea
  • Iron deficiency anemia (a decrease in blood count due to loss of iron)
  • A family history of colon cancer
  • As a follow-up test in people with colon polyps or colon cancer
  • Chronic, unexplained abdominal or rectal pain
  • An abnormal X-ray exam, like a barium enema or CT scan

What To Expect

During colonoscopy, you will lie on your left side on an examination table. In most cases, a light sedative, and possibly pain medication, will be given to help keep you relaxed. Deeper sedation may be required in some cases. The doctor and medical staff monitor vital signs and attempt to make you as comfortable as possible.

The doctor inserts a long, flexible, lighted tube called a colonoscope, or scope, into your anus and slowly guides it through your rectum and into your colon. The scope inflates the large intestine with carbon dioxide gas to give the doctor a better view. A small camera mounted on the scope transmits a video image from inside your large intestine to a computer screen, allowing the doctor to carefully examine the intestinal lining. The doctor may ask you to move periodically so the scope can be adjusted for better viewing.

Once the scope has reached the opening to your small intestine, it is slowly withdrawn and the lining of your large intestine is carefully examined again. Bleeding and puncture of the large intestine are possible but uncommon complications of colonoscopy.

A doctor can remove growths, called polyps, during colonoscopy and later test them in a laboratory for signs of cancer. Polyps are common in adults and are usually harmless. However, most colorectal cancer begins as a polyp, so removing polyps early is an effective way to prevent cancer.

The doctor can also take samples from abnormal-looking tissues during colonoscopy. The procedure, called a biopsy, allows the doctor to later look at the tissue with a microscope for signs of disease.

The doctor removes polyps and takes biopsy tissue using tiny tools passed through the scope. If bleeding occurs, the doctor can usually stop it with an electrical probe or special medications passed through the scope. Tissue removal and the treatments to stop bleeding are usually painless.

What Happens Afterwards?

Colonoscopy usually takes 30 to 60 minutes. Cramping or bloating may occur during the first hour after the procedure. The sedative takes time to completely wear off. You may need to remain at the facility for 1 to 2 hours after the procedure. Full recovery is expected by the next day. Discharge instructions should be carefully read and followed.


The colonoscopy can be used to detect:

  • Colon Polyps
  • Crohn’s Disease
  • Colon Cancer
  • Diverticulosis
  • Irritable Bowel Syndrome

Reprinted and modified from The National Digestive Diseases Information Clearinghouse