What Are the Chances of Complications from Colonoscopy?

 The endoscopic examination of your colon -- the colonoscopy -- is a safe and effective tool intended to diagnose and catch colon cancer early. Like any invasive procedure, it is not without risks. Don't let these risks help you to avoid this screening exam. The colonoscopy is used to find and remove any polyps before they have a chance to grow and potentially cause problems in your bowel. If you have a specific fear of the exam, which people do, talk to your doctor about that concern so he or she can help allay it.


Likewise, although about a third of the people who undergo the test do report some sort of minor gastrointestinal complaint after -- such as gas and bloating -- life threatening complications are rare according to the American Society for Gastrointestinal Endoscopy. As you will take note below, the majority of the most extreme complications only occur in a fraction of the tests completed. 

Bowel Perforation

Simply, a perforation is a hole that can be made by the endoscopy equipment. Bowel perforations are rare, occurring less than one percent of the time. One large study even reported a lower instance of 0.01% cases of perforation. The initial symptoms of a perforation include abdominal pain and swelling. If a perforation is suspected, your doctor will likely order an x-ray or computed tomography (CT) scan to confirm it. Surgery may be indicated to repair the tear in your colon. 

Reaction to Sedation

Although it is possible to have a colonoscopy without sedation, the preferred method is with a form of conscious sedation administered through an intravenous line into a small vein in your hand or forearm.

You will not be "knocked out" as you are during general anesthesia, but most people do report sleeping through the test unfazed. Your risk of a reaction increases if you are elderly or have a history of cardiac or lung disease. Most commonly reported are a decrease in blood pressure, oxygen saturation levels (how well you are breathing), decreased respiratory rate, or changes in heart rhythm and rate.

You are closely monitored by a registered nurse throughout the procedure, and occurrence of a reaction is only reported in 0.9 percent of the cases reviewed. 


Two things can slightly increase your risk of bleeding after a colonoscopy and that includes the use of blood thinners and the removal of any polyps during the procedure. Despite those factors, the overall risk of hemorrhaging is still very minimal at 0.1 to 0.6 percent reported. To decrease your risk, you should be cleared by your cardiologist and allowed permission to stop your blood thinners for a time prior to the exam. Minor bleeding after the procedure is not uncommon, especially if you have had a large polyp removed. Minor bleeding should be self-limiting. In the worst case scenario, excessive bleeding might require blood transfusions or surgical intervention. 


The cause for post procedure infection remains largely unclear. As with any gastrointestinal bug or virus, it is very difficult to actually determine if the colonoscopy procedure was the culprit, or if there was something present prior.

The rate of infections possibly linked to a colonoscopy remains low,  at 0.4 percent, but there is a wide fluctuation in the studies. However, the instance of occurrence is so rare that the American Heart Association nor the American Society for Gastrointestinal Endoscopy encourage taking antibiotics before or after the procedure.

Miscellaneous Complications

There are other, extremely rare complications reported in the studies, but the instance is so microscopic that they don't bear thought when you are trying to weigh the risks against the benefits of a colonoscopy. 


American Cancer Society. (n.d.). Colorectal Cancer Screening Tests. Accessed online June 29, 2015.

American Society for Gastrointestinal Endoscopy. (2011). Guideline: Complications of Endoscopy. Accessed online June 28, 2015.

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