Johns Hopkins Health Alert
Irritable Bowel Syndrome and the Risk of Colon Cancer
Recently a reader of our Health After 50 newsletter asked us: “My doctor recently diagnosed me with irritable bowel syndrome. Do I have a greater risk of developing colon cancer?” Here’s what we know …
The short answer to this question is “no.” People with irritable bowel syndrome (IBS) suffer from chronic diarrhea, chronic constipation -- or both, and abdominal pain. Before diagnosing irritable bowel syndrome, doctors may perform a colonoscopy to rule out colon cancer and conditions such as ulcerative colitis and Crohn's disease, which cause inflammation of the colon. People with Crohn's disease and ulcerative colitis do have a slightly higher chance of developing colon cancer, but that's not the case for people with IBS.
In a recent study published in the American Journal of Gastroenterology, researchers compared colonoscopy results of 466 participants with irritable bowel syndrome symptoms with those of 451 participants without irritable bowel syndrome. Results showed that people with suspected irritable bowel syndrome were actually less likely to be diagnosed with adenomas -- benign but abnormal colon growths that, if not removed, can lead to cancer. In fact, the adenoma rate was 26.1 percent for people without irritable bowel syndrome versus just 7.7 percent for people with suspected irritable bowel syndrome. (People with irritable bowel syndrome don't necessarily have a lower risk of developing cancer. The irritable bowel syndrome group was younger and some people in the non- irritable bowel syndrome group were at a higher risk for cancer owing to previous adenomas.)
Cancer notwithstanding, people with irritable bowel syndrome and chronic diarrhea should ask their doctor about microsopic colitis—an inflammation of the lining of the colon caused by the buildup of either collagen or white blood cells. The chief symptom of microscopic colitis is chronic diarrhea. Because inflammation associated with microscopic colitis is not recognizable during routine colonoscopy, it's not uncommon for it to be misdiagnosed as IBS with chronic diarrhea. The only way to diagnose microscopic colitis, which is treated differently than IBS, is to view samples of colon tissue under a microscope. The American College of Gastroenterology therefore stresses that during colonoscopy everyone suspected of having IBS with chronic diarrhea should receive a series of biopsies.
Posted in Digestive Health on November 8, 2010
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