Ulcerative colitis: a plain-English guide

What is ulcerative colitis?

Ulcerative colitis is a type of inflammatory bowel disease (IBD) that causes long-term inflammation and ulcers (sores) in the lining of the large intestine (colon) and rectum. Unlike Crohn's disease, UC affects only the colon and always starts in the rectum, often spreading upward.

UC is a chronic condition, meaning it lasts a long time. It typically involves periods of active symptoms (called flares) and periods with little or no symptoms (called remission). Most people with UC can manage their condition effectively with the right treatment.

Who gets ulcerative colitis?

UC can affect anyone, but it most commonly develops in people between ages 15 and 30. It affects men and women roughly equally. In the United States, an estimated 600,000 to 900,000 people live with UC. Family history of IBD is a risk factor, but most people with UC have no affected relatives.

Types of ulcerative colitis

Doctors classify UC by how much of the colon is affected:

• Ulcerative proctitis: Inflammation limited to the rectum. Usually causes milder symptoms.
• Left-sided colitis: Inflammation extends from the rectum up the left side of the colon.
• Pancolitis (extensive colitis): Inflammation affects the entire colon. Symptoms tend to be more severe.

How is UC different from Crohn's disease?

Both UC and Crohn's are forms of IBD, but they differ in important ways. UC affects only the colon and its lining, while Crohn's can affect any part of the digestive tract from mouth to anus — and all layers of the bowel wall. The treatment approaches can also differ.

How is ulcerative colitis diagnosed?

There is no single test for UC. Your doctor will likely use a combination of:

• Blood tests (to check for inflammation or anemia)
• Stool tests (to rule out infections)
• Colonoscopy or sigmoidoscopy (to view the colon lining and take biopsies)
• Imaging (CT or MRI in some cases)

When to contact a doctor

Contact your healthcare provider if you have persistent diarrhea, blood in stool, significant abdominal pain, unexplained weight loss, or fatigue that affects daily life. Early diagnosis and treatment can help prevent complications.