Ulcerative colitis (UC) is a chronic inflammatory bowel disease that causes continuous inflammation and ulceration of the colon’s inner lining. Symptoms typically wax and wane, with flares of bloody diarrhea, urgency, and abdominal cramping. UC is distinct from Crohn’s disease, which can affect any part of the gastrointestinal tract.
Causes are multifactorial, involving immune dysregulation in genetically susceptible people interacting with environmental triggers and the gut microbiome. Risk is higher with family history, certain ethnic backgrounds, and in regions with westernized lifestyles. Onset is most common between ages 15 and 30, with a smaller peak later in life; both sexes are affected. Smoking history differs from Crohn’s disease—former smokers have an increased risk of UC compared with current smokers—though smoking is not recommended as a treatment. (NIDDK)
Clinical presentation ranges from mild rectal bleeding and urgency to severe, frequent bloody stools with systemic signs such as fever, anemia, and weight loss. Extraintestinal manifestations may involve the joints, skin, eyes, and liver (including primary sclerosing cholangitis). Disease extent is categorized as proctitis (rectum), left-sided colitis (up to the splenic flexure), or extensive/pancolitis, which influences symptoms and management. A complete list of signs includes abdominal pain or cramping, frequent diarrhea often with blood or pus, urgent need to have a bowel movement, rectal bleeding, weight loss, fatigue, fever, reduced appetite, dehydration, and anemia. (Cleveland Clinic)
Diagnosis integrates history, labs, stool studies to exclude infection, and endoscopy with biopsy. Colonoscopy or flexible sigmoidoscopy shows continuous, superficial inflammation with mucosal friability and ulceration; biopsies confirm features of chronic colitis. Blood tests assess anemia and inflammation; fecal calprotectin helps gauge intestinal inflammation and monitor response. Imaging may be used to evaluate complications but is not the primary diagnostic tool. (Mayo Clinic)
Treatment is individualized to disease extent and severity, with the twin goals of inducing remission and maintaining it while healing the mucosa. For mild to moderate disease, 5-aminosalicylates (oral and/or rectal mesalamine) are first-line, particularly for proctitis and left-sided colitis. Corticosteroids—topical, oral, or short courses of systemic therapy—treat flares but are not used for maintenance due to side effects. For steroid-dependent or moderate to severe disease, options include immunomodulators (thiopurines) and advanced therapies such as tumor necrosis factor (TNF) inhibitors, anti-integrin agents, interleukin-12/23 or 23 inhibitors, and Janus kinase (JAK) inhibitors; selection depends on prior response, comorbidities, and risk profile.
Supportive care is integral. Iron, vitamin D, and other deficiencies are corrected; antidiarrheals are used cautiously; and vaccines are updated prior to or during immunosuppressive therapy as indicated. Nutrition emphasizes balanced intake and hydration; no single “UC diet” suits everyone, but some find symptom relief by avoiding trigger foods during flares. Mental health support and stress reduction can improve quality of life alongside medical therapy.
Complications include severe bleeding, toxic megacolon, perforation, and increased risk of colorectal cancer with longstanding, extensive colitis—particularly in the presence of primary sclerosing cholangitis. Regular colonoscopic surveillance is recommended after several years of disease, with intervals tailored to individual risk factors and prior findings; detection and removal of dysplasia reduce cancer risk. Hospitalization is sometimes required for acute severe colitis, treated with intensive medical therapy and close monitoring.
Surgery is curative for colitis because the disease is confined to the colon and rectum. Indications include medically refractory disease, dysplasia or cancer, and life-threatening complications. Procedures range from total proctocolectomy with end ileostomy to restorative proctocolectomy with ileal pouch–anal anastomosis (IPAA). Advances in medical therapy have reduced the need for surgery for many, but timely referral remains important when goals of care are not met or complications arise.
Prognosis has improved with modern treat-to-target strategies that aim for symptomatic remission and objective mucosal healing. Many individuals maintain work, school, and family roles with appropriate therapy and monitoring. Regular follow-up with an IBD-experienced clinician, adherence to treatment, vaccination and infection-prevention measures, and colon cancer surveillance are central to long-term outcomes.
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