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DEAR MAYO CLINIC:

What's the difference between ulcerative colitis and Crohn's disease?

ANSWER:

Ulcerative colitis and Crohn's disease are both forms of inflammatory bowel disease (IBD). It can sometimes be difficult to differentiate between the two conditions. It's important to work with specialists familiar with both ulcerative colitis and Crohn's disease to get the right diagnosis, because treatment that works for one may not be effective for the other.

It can be helpful to think of IBD on a spectrum, with ulcerative colitis at one end and Crohn's disease at the other. Ulcerative colitis usually affects only the innermost lining of the large intestine (colon) and rectum, and occurs continuously from the rectum into the colon. The disease can be limited to just the rectum, the rectum and the left side of the colon or it may affect the entire colon. In contrast, Crohn's disease occurs in patches throughout the digestive tract. Crohn's often spreads deep into the layers of affected bowel wall and may penetrate the entire bowel wall to involve other organs.

Diagnosing ulcerative colitis or Crohn's disease involves a thorough medical evaluation that includes a variety of diagnostic tests. Those tests may include blood tests, a stool sample, colonoscopy or sigmoidoscopy, and an abdominal CT scan or MRI scan.

In some cases, IBD is clearly Crohn's or it's clearly ulcerative colitis. But, if a person has features of both (a condition known as indeterminate colitis), it's critical that an accurate determination be made regarding which end of the spectrum the person is closest to, because successful treatment relies on a correct diagnosis. For example, medications are available that often work well for Crohn's disease, and there are also medicines that can be effective for treating ulcerative colitis. But the different medications don't necessarily work well for both conditions.

In addition, people who have severe cases of ulcerative colitis can often be cured with surgery. Because ulcerative colitis affects only the rectum and colon, surgically removing both can eliminate the disease. Traditionally, the surgery required an ostomy, where the end of the bowel is attached to front of the abdomen and stool is collected in an external device. However, with an experienced surgeon, many patients can now avoid a permanent ostomy. Surgeons can construct a pouch using the small intestine, put it into the pelvis and connect it to the anus. This makes a permanent ostomy unnecessary. Furthermore, in many cases this surgical procedure can be performed using a minimally invasive approach which improves recovery. Following ulcerative colitis surgery, most people can return to their usual activities and don't require any medications.

A surgical cure isn't possible with Crohn's disease, and removing the colon and rectum typically isn't an effective long-term treatment. Crohn's disease affects the entire intestine, and symptoms usually appear in different areas over time. If medication isn't effective or if the symptoms related to a segment of intestine are severe, then surgery may be an option. But it's important to have a surgeon with expertise in treating Crohn's disease. There are a variety of techniques that an experienced surgeon can use to preserve the amount of bowel that remains, and there's considerable planning that needs to happen for subsequent surgeries to be successful.

If you have IBD, the bottom line is that you need a team of specialists working together who can provide an accurate diagnosis and the most effective treatment. That team should include a gastroenterologist -- one who is experienced in and focuses on IBD and its treatment -- and a surgeon with expertise in treating both Crohn's and ulcerative colitis. Using that type of collaborative, multidisciplinary approach is the best way to ensure successful care for these diseases.

Robert Cima, M.D., M.A., Colon & Rectal Surgery, Mayo Clinic, Rochester, Minn.

Medical Edge from Mayo Clinic is an educational resource and doesn't replace regular medical care.

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