Ulcerative colitis (UC) is a type of inflammatory bowel disease that causes inflammation in the colon, also called the large intestine. The type of UC symptoms you experience may depend on where inflammation is occuring in the colon.
“Ulcerative colitis may have distribution in different portions of the large intestine,” says Sergey Khaitov, MD, surgeon at Mount Sinai Beth Israel.
The entire digestive tract can look like a twisting mess of organs, but the large intestine itself is fairly simple in comparison. Imagine the large intestine like a table with two legs and a top. One leg is the ascending colon, the tabletop is the transverse colon, and the other leg is the descending colon. Another small portion called the sigmoid colon connects the descending colon to the rectum.
Doctors have defined four types of UC based on which of those segments of the colon are inflamed. “By definition, ulcerative colitis starts at the very end of the colon, and can extend farther towards the beginning,” says Todd B. Linden, MD, gastroenterologist.
Ulcerative proctitis causes inflammation in the rectum only, which is located at the very end of the colon. This type affects the smallest amount of the colon.
Proctosigmoiditis causes inflammation in the rectum and the lower segment of the colon (the sigmoid colon). This type of UC is known for causing more digestive distress: bloody stool, diarrhea, cramps, and tenesmus—the constant urge to have a bowel movement (even if your bowels are empty). Tenesmus may lead to straining, cramping, and pain.
Left-sided colitis causes continuous inflammation from the rectum through the ascending colon. The end of the ascending colon—where it bends into the transverse colon—is called the splenic flexure (due to its proximity to the spleen). Left-sided colitis is associated with loss of appetite and weight loss, in addition to the typical UC symptoms.
Pan-ulcerative colitis affects the entire colon. Inflammation is continuous—with no unaffected patches—from the rectum to the start of the colon. This type of UC is associated with a higher risk of complications, especially toxic megacolon, and the need for surgery. Pan-ulcerative colitis may cause pain, diarrhea, and extreme weight loss.
Symptoms may vary depending on which type of UC the individual has, but pan-ulcerative colitis is not necessarily more severe than proctosigmoiditis. “There’s also no correlation between ... the extent of involvement in the colon and how severe it is,” says Dr. Linden. “Some people may have very severe colitis, even though it’s only in a few centimeters [of the colon].”
The type of UC a patient has will determine what kind of treatment plan is most beneficial. The goal of UC treatment is to reach and maintain remission (a period of no symptoms), but the methods of finding remission may not look the same for each individual. Learn more about treatment for UC here.
One thing to remember is that treatment for UC has improved, and people who have it can often enjoy a high quality of life. “Things have improved dramatically, and the vast majority of people will be totally in remission and happy and healthy and unbothered by this for the rest of their life,” says Dr. Linden.
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