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There is a small chance for problems from a colonoscopy. The scope or a small tool may tear the lining of the colon or cause bleeding.

After the test

After the test, call your doctor immediately if you:

  • Have heavy rectal bleeding.
  • Have severe belly pain.
  • Develop a fever.
  • Are very dizzy.
  • Are vomiting.
  • Have a swollen and firm belly.


Colonoscopy is a test that allows your doctor to look at the inner lining of your large intestine (rectum and colon). If a sample of tissue (biopsy) was collected during the colonoscopy, it will be sent to a lab for tests.

  • Samples of colon tissue are usually sent to a pathology lab, where they are looked at under a microscope for diseases.
  • Other samples of colon tissue may be sent to a microbiology lab to see whether an infection is present.

Your doctor may be able to tell you the results immediately after the procedure. Other test results are ready in 2 to 4 days. Test results for certain infections may be ready in several weeks.


The lining of the colon looks smooth and pink, with a lot of normal folds. No growths, pouches, bleeding, or inflammation are present.


Some abnormal findings of colonoscopy include hemorrhoids (the most common cause of blood in the stool), polyps , cancer , one or more sores (ulcers), pouches in the wall of the colon (diverticulosis), or inflammation. A red, swollen lining of the colon (colitis) may be caused by infection or inflammatory bowel disease (IBD).

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

  • Having a barium enema within a week before the test. Barium can block your doctor's view of the colon.
  • Not doing a good colon prep before the test. If you still have stool (feces) in the colon, your doctor may cancel the test and you will have to reschedule and do the colon prep again.
  • Having a colon that has many turns, past surgery on the colon, or a lot of pain during the test.
  • Taking iron supplements. This may make your stool turn black and make it hard to clean out the colon. Do not take iron supplements for several days before a colonoscopy.
  • Drinking red or purple fluids, such as grape juice or fruit punch.
  • Eating red or purple foods, such as grape ice pops or cherry gelatin.
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WebMD Medical Reference from Healthwise

Last Updated: November 14, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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