What is the difference between irritable bowel syndrome and inflammatory bowel disease? How would I know if I have either one of these?

Irritable bowel syndrome (IBS) is a common though uncomfortable disorder of the colon or rectum. While the basic cause of IBS is unknown, researchers have found that the colon muscle in people with IBS contracts more readily than in people without IBS. A number of factors can "trigger" IBS, including certain foods, medicines, and emotional stress. IBS is not a life-threatening condition and does not make a person more likely to develop other colon conditions, such as colitis, Crohn's disease, or colon cancer.

Symptoms of IBS include:

  • Abdominal pains or cramps (usually in the lower half of the abdomen)
  • Excess gas
  • Harder or looser bowel movements than average
  • Diarrhea, constipation, or alternating between the two

Symptoms of IBS DO NOT include bleeding or black stools.

Inflammatory bowel disease (IBD) most often refers to Crohn's disease and ulcerative colitis, but also might be referred to as colitis, enteritis, ileitis, and proctitis. Both Crohn's disease and ulcerative colitis cause inflammation of the bowel.

Crohn's disease is a chronic illness in which the intestine (bowel) becomes inflamed and ulcerated (marked with sores). Crohn's disease typically begins in the lower part of the small intestine (ileum), although it can occur in any part of the large or small intestine, stomach, or esophagus. Crohn's disease affects the entire thickness of the walls of the bowel, explaining why patients with Crohn's disease are prone to developing fistulas and abscesses. In addition, sections of diseased bowel can be interrupted by sections of healthy bowel.

The symptoms of Crohn's disease depend on where the disease occurs in the bowel and its severity. In general, symptoms include:

  • Chronic diarrhea
  • Weight loss
  • Fever
  • Abdominal pain and tenderness (often on the right side of the lower abdomen)
  • Feeling of a mass or fullness in the lower, right abdomen

Ulcerative colitis occurs only in the large intestine and typically follows an unbroken pattern. Ulcerative colitis affects only the large intestine. It does not affect the esophagus, stomach, or small intestine. It affects only the inner layer of the colon (mucosa), and does so in a continuous pattern. The inflammation begins in the rectum and then spreads to other segments of the colon.

The main symptom of ulcerative colitis is diarrhea, which subsequently becomes bloody. Occasionally the symptoms of ulcerative colitis include severe bloody diarrhea, abdominal pain, and fever.

If you suspect you have IBS or IBD, it is important to see your health care provider. Your provider should review your medical history and perform a physical examination. To diagnose IBD, one or more of the following tests might be ordered:

  • Blood tests
  • Stool samples
  • Endoscopic examination of the colon with biopsies
  • CT scanning

Last reviewed by a Cleveland Clinic medical professional on 03/14/2012.

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