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The two primary forms of inflammatory bowel disease (IBD), Crohn’s disease and ulcerative colitis, are often lumped together, but some of their characteristics are very different. The two diseases share many symptoms, but are their treatments, both medical and surgical, are not the same. In many cases, a trained gastroenterologist (armed with various test results) can determine whether a case of IBD is either Crohn’s disease or ulcerative colitis. However, there are cases where the diagnosis of one form of IBD over the other is very difficult. At times, a final diagnosis is possible only after an event during the course of the disease or its treatment makes the form of IBD readily apparent.
Patients with IBD may be very confused as to the differences between these diseases. As with any chronic condition, education is an important tool that can be used to become an active (rather than a passive) participant in one’s own treatment plan. The main differences between ulcerative colitis and Crohn’s disease are described below.
Location of inflammation
In Crohn’s disease, the location of the inflammation may occur anywhere along the digestive tract from the mouth to the anus. In ulcerative colitis, the large intestine (colon) is typically the only site that is affected. However, in some people with ulcerative colitis the last section of the small intestine, the ileum, may also show inflammation.
Many symptoms of ulcerative colitis and Crohn’s disease are similar, but there are some subtle differences. ulcerative colitis patients tend to have pain in the lower left part of the abdomen, while Crohn’s disease patients commonly (but not always) experience pain in the lower right abdomen.
With ulcerative colitis, bleeding from the rectum during bowel movements is very common, and bleeding is much less common in patients with Crohn’s disease.
Pattern of inflammation
The pattern that each form of IBD takes in the digestive tract is very distinct. Ulcerative colitis tends to be continuous throughout the inflamed areas. In many cases, ulcerative colitis begins in the rectum or sigmoid colon, and spreads up through the colon as the disease progresses. In Crohn’s disease, the inflammation may occur in patches in 1 or more organs in the digestive system. For instance, a diseased section of colon may appear between two healthy sections.
During a colonoscopy or sigmoidoscopy, the physician can view the actual inside of the colon. In a colon that has Crohn’s disease activity, the colon wall may be thickened and, because of the intermittent pattern of diseased and healthy tissue, may have a “cobblestone” appearance. In ulcerative colitis, the colon wall is thinner and shows continuous inflammation with no patches of healthy tissue in the diseased section.
Granulomas are inflamed cells that become lumped together to form a lesion. Granulomas are present in Crohn’s disease, but not in ulcerative colitis. Therefore, when they are found in tissue samples taken from an inflamed section of the digestive tract, they are a good indicator that Crohn’s disease is the correct diagnosis.
In ulcerative colitis, the mucus lining of the large intestine is ulcerated. These ulcers do not extend beyond this inner lining. In Crohn’s disease, the ulceration is deeper and may extend into all the layers of the bowel wall.
In Crohn’s disease, strictures, fissures, and fistulas are not uncommon complications. These conditions are less frequently found in cases of ulcerative colitis.
One of the more confounding aspects of IBD is its interaction with cigarette smoking or tobacco. Smoking is associated with a worse disease course in Crohn’s disease patients and may increase the risk of relapses and surgery. For some people with ulcerative colitis, smoking has a protective effect, though smoking is NOT recommended due to its significant health risks. Ulcerative colitis is often called a “disease of non-smokers.”
In many cases, the drugs used to treat Crohn’s disease and ulcerative colitis are similar, however there are some medications that are more effective for one form of IBD over the other. The mainstays of treatment for ulcerative colitis include 5-ASA medications and corticosteroids. The 5-ASA drugs are typically not used to treat Crohn’s disease, though corticosteroids are. Some medications are only approved to treat one form of IBD or the other. For instance, Cimzia (certolizumab pegol) is only approved to treat Crohn’s disease, and Colazal (balsalazide disodium) is only approved to treat ulcerative colitis. Other newer drugs, including Humira (adalimumab) and Entyvio (vedolizumab), are approved for both Crohn’s disease and ulcerative colitis.
For patients with Crohn’s disease, surgery to remove diseased sections of bowel may provide some relief from symptoms, but the disease tends to recur. Because the inflammation only occurs in the large intestine in ulcerative colitis, the removal of that organ (called a colectomy) is considered a “cure.” Removing only part of the colon is not usually done with ulcerative colitis patients, as the disease will recur in the portion of the colon that is left.
After a colectomy, an ulcerative colitis patient may have an ileostomy or one of several types of internal pouches created from healthy small intestine. Internal pouches are not typically not created in Crohn’s disease patients who must undergo colectomy, because the Crohn’s disease may occur in the pouch. If the pouch became inflamed it would have to be removed in another surgery.
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