Study puts colonoscopy risks into perspective

To hear your doctor recommend a “colonoscopy” can send chills down most peoples’ spines. The procedure, which involves a doctor sending a little camera fixed to the end of a flexible tube through the colon and into the intestines, can make even the strongest folks a bit uncomfortable. Some even fear that the procedure itself can cause harm. One study hopes to put those fears into perspective.

Colonoscopies serve an important purpose – identifying colon polyps even before they are cancerous, in some cases virtually eliminating one’s chances of getting colorectal cancer. Because most cancers of the colon and rectum don’t present symptoms until the later stages, when it is most deadly, doctors recommend patients receive regular colon screenings by colonoscopy beginning at age 50 or earlier if they have a family history or are showing suspicious symptoms.

The procedure is generally safe. One of the biggest concerns expressed by patients is colonoscopic perforation (CP), or bowel perforation caused by equipment used during the colonoscopy exam. While CP is an important part of the benefit-harm calculation of colonoscopy, especially those who do not present symptoms, the risk of CP is rare, occurring in only 1 out of 1,700 procedures.

One study pulled data from more than 10,000 patients undergoing either a colonoscopy or flexible sigmoidoscopy at the Faculty of Medicine Siriraj Hospital in Bangkok, Thailand, between January 2005 and July 2008. It found that over that 3.5-year period only 15 CPs occurred among 10,124 patients who underwent the procedure, or 0.15 percent. Variables such as patient gender, emergency endoscopy, anesthetic method, and the specialty or experience of the endoscopist did not seem to play a role in the outcomes. However, patients over 75 years of age and those who received therapeutic endoscopy were at higher risk of CP.

Older patients also are more likely to suffer from a severe adverse reaction to a type of laxative that is either prescribed to patients or sold over-the-counter to cleanse the bowel prior to a colonoscopy. That type of laxative, known as oral sodium phosphate, or OSP, has been linked to a serious form of kidney injury known as acute phosphate nephropathy. Prescription brands of OSP, such as Visicol and Osmo Prep, now carry a black box warning, and over-the-counter OSP products, such as those made by Fleet, have been pulled from store shelves. While older patients and women are at higher risk from kidney injury from OSPs, younger patients have also experienced kidney problems often weeks or months following use of the OSPs.