Why Ulcerative Colitis Causes Diarrhea

Ulcerative colitis is a chronic inflammatory bowel disease that primarily affects the colon and rectum, and one of its most common symptoms is diarrhea. This condition leads to frequent, loose, and watery stools due to several key factors related to inflammation and damage in the digestive tract.

Inflammation and ulcers in the colon lining can result in increased secretion of fluid into the intestines. As the disease progresses, the mucosal layer becomes damaged with erosions and ulcers, which stimulate the glands in the colon to secrete excessive amounts of liquid. This additional fluid overwhelms the colon's ability to absorb it, leading to diarrhea.

Another contributing factor is the impaired absorption function of the colon. The colon normally absorbs water from digested food to form solid stool, but in ulcerative colitis, this process is disrupted. Because the inflamed intestinal lining cannot effectively absorb water, the stool remains loose and watery, worsening the condition of diarrhea.

Lastly, the rectum and anus are often affected by the inflammation as well. This results in heightened sensitivity and a reduced capacity to hold stool, causing an increase in bowel movements. Patients may feel a strong urgency to defecate multiple times a day, even when there is little stool to pass.

In summary, diarrhea in ulcerative colitis is mainly caused by excessive fluid secretion, reduced water absorption in the colon, and increased frequency of bowel movements due to rectal involvement. Understanding these mechanisms can help guide treatment strategies aimed at managing symptoms and improving quality of life.