A doctor may order a colonoscopy to help diagnose ulcerative colitis (UC), check for complications of UC, or see whether the condition is progressing.

UC is a type of inflammatory bowel disease that causes inflammation and lesions in the large intestine, including the rectum, colon, or both.

A doctor may also order a colonoscopy to check for signs of colorectal cancer, which affects people with UC at higher rates than people without the condition.

The American College of Gastroenterology recommends that people who have UC that extends beyond the rectum get a colonoscopy to check for signs of colorectal cancer every 1–3 years, beginning 8 years after diagnosis.

The procedure primer below shows what a colonoscopy involves.