My older sister recently underwent emergency surgery to remove portions of her small intestine and her colon. She has been diagnosed with Crohn's disease. About three years ago, I was diagnosed with irritable bowel syndrome. I have just learned to live with the diarrhea because I do not like the Imodium AD the doctor told me to take. Is it possible that I have been misdiagnosed? Should I be checked for Crohn's disease?

K.

Crohn's disease is a chronic inflammatory disease affecting the small and large intestine. Patients suffer from chronic diarrhea (sometimes with rectal bleeding), abdominal pain, weight loss and fevers. The diagnosis is often made when a colonoscopy is done to evaluate these symptoms. In other cases, a barium exam of the small intestine is ordered to investigate these complaints, and the diagnosis is made based on that. Finally, some people may suddenly be stricken by one the complications of Crohn's, such as obstruction of the intestine, and the diagnosis is made when the patient is taken to the operating room. Although the cause of Crohn's is still unknown, we do know that there is a higher incidence of this disease in families of affected patients.

Irritable bowel syndrome (IBS) is a common diagnosis made based on a certain constellation of symptoms, including cramping abdominal pain, abdominal bloating, increased mucus in the stool, and alternating diarrhea and constipation. This diagnosis should be made only after tests are performed to rule out other diseases. IBS is not progressive, meaning it does not become more severe or complicated with time. It is treated with medications to relieve whatever symptoms a particular patient happens to suffer -- for example, the Imodium AD recommended for your diarrhea. The exact cause of IBS is not known. However, it probably relates to abnormal muscle contractions in the colon, along with a heightened sensitivity to pain in the intestines of certain patients.

In evaluating someone with symptoms such as yours, it is very important to rule out a progressive disorder, such as Crohn's, before making the diagnosis of IBS. Factors that may point to diseases other than IBS include significant weight loss, blood in the stool, vomiting, fever and diarrhea that wakes the patient up at night.

That said, IBS is a very common disease. You should follow up with your doctor and discuss your concerns with him. If any questions remain regarding your diagnosis or the tests that were performed before arriving at the diagnosis, then a referral to a gastroenterologist may be in order.