What’s the Difference Between Crohn’s Disease and Ulcerative Colitis?

Crohn’s disease (CD) and ulcerative colitis (UC) are the two most common types of inflammatory bowel diseases (IBD). While these conditions produce very similar symptoms and use similar type of therapies, they are not the same. In ulcerative colitis, only the colon is affected; and in particular, only the innermost lining of the colon, the mucosa, becomes inflamed. It also spreads proximally, meaning it starts from the rectum and can spread continuously to the rest of the colon. Crohn’s disease, on the other hand, may affect any part of the GI tract, from the lips to the anus. Unlike UC, it can skip large segments of the bowel before reappearing in others. The areas most affected, however, are the lower part of the small intestine (the ileum) and the large intestine (the colon). Also, in CD, the inflammation doesn’t stop at the mucosa level and may burrow through the full thickness of the bowel wall. In some patients, it is difficult to determine whether their IBD is CD or UC – even after testing.  In up to 10% of case, there are overlapping features of both, a condition called indeterminate colitis (IC). Typical symptoms of IBD include abdominal pain, cramping, diarrhea, rectal bleeding, fecal urgency, and fatigue. These are the result of chronic inflammation of the intestines. In 25-40% of patients, the classic signs and symptoms of IBD may be accompanied by symptoms in the eyes, joints, skin, bones, kidneys, and liver. These non-bowel symptoms are called extraintestinal manifestations (EIMs). Children who develop IBD often have growth problems, without overt signs of an inflamed bowel. Because the gut has only a limited number of ways to show distress, many of the above symptoms are non-specific and could also be related to other gastrointestinal (GI) conditions.  These include but are not limited to: infectious gastroenteritis, traveler’s diarrhea, celiac disease, gallbladder disease, pancreatitis, stomach ulcers, irritable bowel syndrome (IBS), and colorectal cancer. Ruling out other possible diseases is part of the diagnostic work-up. The typical work up will include an initial provider visit with someone in the field of gastroenterology – who is the most qualified health care specialist to diagnose IBD. A physical exam will focus on the GI tract and detailed family/social history will be obtained too.  Specialists commonly use blood and stool tests as part of the diagnostic work-up.  Endoscopy/colonoscopy are procedures that let your provider look into your body. They use instruments called upper endoscopes and colonoscopes. They have a tiny camera attached to a long, thin, flexible tube that allows the GI specialist to see images of the intestines magnified on a monitor. This helps the physician see if inflammation is present, where it is located, assess its severity, and obtain biopsies to hopefully confirm the diagnosis. Endoscopy/colonoscopy are also vital for monitoring therapy – healing of the lining of the intestine is a sign that the medication is working. As is the case with laboratory tests, diagnostic imaging may also play multiple roles in treating and managing IBD. Not only will the radiology scans help to determine if you have CD or UC, but they will also reveal the extent and severity of the inflammatory process and assess complications such as an obstruction, fistula, or abscess. This information will allow your provider to recommend the best course of therapy. For more information on IBD, please visit www.crohnscolitisfoundation.org. Author: You Sung Sang, M.D., FACG, AGAF