I've been told I have irritable bowel syndrome. I get a recurrent pain in my lower right side about every six months. During these attacks, I sometimes run a low fever -- about 99.6 to 100 -- but test results show no sign of appendicitis. Retrocecal appendix runs in my family, along with Crohn's disease. Could my problem possibly be Crohn's? Would it be prudent to get a second opinion on the diagnosis of irritable bowel syndrome?

R.

Irritable bowel syndrome (IBS) is a common cause of abdominal complaints such as pain, cramping, diarrhea and constipation. Often the symptoms are related to stress and may worsen with eating and improve with defecation. It is unclear what causes this constellation of symptoms. Some speculate that one factor may be a colon or small intestine that is extremely sensitive to various stimuli, such as distention. Although IBS is common, there is no diagnostic test for it. A doctor can make a diagnosis of IBS only after ruling out other diseases with various tests.

IBS is a disease that does not progress, but it may have periods in which it worsens or improves. Some patients find relief with fiber supplements, antispasmodic medications, antidepressants or antianxiety medications.

Symptoms that are not usual in IBS include nausea, vomiting, fever, unintentional weight loss, loss of appetite, pain that wakes the patient up at night, or nighttime diarrhea that causes the patient to soil the bed. Your intermittent bouts of pain and fever are not typical of IBS. Although appendicitis can cause this, it is unusual that it would recur months later. Retrocecal appendix is not a problem in itself. It just means that the appendix is located under the colon on the right side, which means the pain associated with appendicitis may be in the right upper abdomen instead of the usual location in the lower abdomen.

However, your complaints could be consistent with Crohn's disease. Crohn's is an inflammatory disease of the colon and small intestine that most commonly involves the ileum (last part of the small intestine) and cecum (first part of the colon). These structures are located in the right lower abdomen. Crohn's typically begins with several months of intermittent pain, often with fevers, diarrhea and weight loss. The disease also has a familial predilection, so your family history is significant.

Another possible source of your symptoms could be an infection of the bowel, which may be localized to one area. Diverticulitis, an inflammation of small pouches in the colon, can also produce your symptoms. These pouches are more common in older patients -- you did not state your age. Finally, if you are female, your symptoms might be gynecologic rather than gastrointestinal.

Various tests can help a doctor determine whether you have any of these conditions. A CT scan of the abdomen and pelvis is often done to look for appendicitis or diverticulitis and may also pick up signs of Crohn's. A barium study of the small intestine and/or colon can also detect changes caused by Crohn's. A colonoscopy would confirm the diagnosis and can also find signs of colonic infection, if present.

I wonder what tests were done in evaluating your pain. If your diagnosis of IBS was made without excluding other diseases, such as the ones mentioned, you would benefit from a second opinion.