Colonoscopy, Complications, and Consent
A colonoscopy is a medical procedure that allows your doctor to examine completely the lining of your colon (large intestine) for abnormalities such as polyps, tumors, and inflammatory bowel disease. This is done by inserting a thin flexible tube into the anus and advancing it slowly into the rectum and colon. In most cases, polyps can be removed completely at the time of colonoscopy. A complete colonoscopy may take 15 to 30 minutes or more, but with sedation, you are not aware of the passage of time. Common side effects of colonoscopy are not serious, and serious complications are rare.
Colonoscopy is a safe procedure. The most common complaint is gas or cramps following the procedure. This usually resolves spontaneously within a few minutes to a few hours, following the passage of gas (flatus) in the usual way. If there is pain that is severe, prolonged, or accompanied by a fever, call the doctor immediately to make sure there is not a complication, and for instructions what to do.
Perforation (making a hole in the colon) is a rare but serious complication that occurs in 0.2% to 0.4% of diagnostic colonoscopies [1 in 500, to 1 in 250], and up to 1% after removal of a polyp [1 in 100]. Small perforations may be managed medically, but large perforations, which are rare, will require surgery, possibly including a temporary colostomy ("bag").
Bleeding is rare following a polypectomy, but may occur in 0.7% to 2.5% [7 - 25 per 1000].
Bleeding may occur immediately, or within the next 2 weeks. Most bleeding stops by itself, but occasionally requires transfusion and/or repeat colonoscopy in order to stop the bleeding. Aspirin, coumadin, Plavix or other blood thinners increase the risk and severity of bleeding. You need to discuss any such medications with your doctor, for instructions.
Reactions to medications during colonoscopy are rare, and may include prolonged sedation, respiratory depression, cardiac rhythm disturbances, and soreness at the site of medication injection.
Death is extremely rare, with or without polypectomy, and in one series occurred in 0.006% [five deaths in 83,725 procedures]. However unlikely, legally you need to be advised of this possibilty.
Colonoscopy is an accurate procedure. Given an adequate bowel prep, a complete colonoscopy should be able to find most, if not all of the polyps present. The smaller the polyp, the greater the chance of missing it. Such small polyps are likely to be found at your next screening colonoscopy without significant risk of missing a cancer. CT colography ("virtual colonoscopy") cannot diagnose polyps 5mm in size or less. The American Society for Gastrointestinal Endoscopy and the American College of Gastroenterology have defined a number of "quality indicators" for colonoscopy with respect to its effectiveness in reducing the incidence of colorectal cancer. This depends on adequate visualization of the entire colon, diligence in examining the entire lining of the colon, and patient acceptance of the procedure. Longer withdrawal times, once the colonoscope has been inserted completely to the far end of the colon, have been demonstrated to improve polyp detection rates. Conversely, rapid withdrawal may miss lesions and reduce the effectiveness of colon cancer prevention. Thus, careful examinations at appropriate intervals are necessary to optimize the effectiveness of colonoscopy in reducing the incidence of colorectal cancer.