Ulcerative Colitis

What happens in ulcerative colitis

In UC, the immune system reacts abnormally to bacteria and other triggers in the colon, causing continuous inflammation of the inner lining (mucosa). The inflammation always involves the rectum and extends upward without skipped areas. The inflamed lining bleeds, produces mucus and cannot absorb water properly, causing bloody diarrhea.

The exact cause is unknown. Genes, the gut microbiome, the immune system and environmental factors all contribute.

Types by extent

Symptoms

• diarrhea, often with blood or mucus
• urgency and incontinence
• tenesmus: frequent feeling of needing to pass stool
• cramping lower belly pain, often eased by a bowel movement
• night-time bowel movements
• fatigue and weight loss
• fever in severe flares

Effects outside the gut

• joint pain and arthritis, including ankylosing spondylitis
• eye inflammation (uveitis, episcleritis)
• skin conditions: erythema nodosum and pyoderma gangrenosum
• mouth ulcers
• liver disease: primary sclerosing cholangitis
• anemia from blood loss
• blood clots
• osteoporosis, especially with steroid use

Risk factors

• age 15 to 30, with a second peak at 50 to 70
• family history of IBD
• Ashkenazi Jewish ancestry
• living in industrialized countries
• former smokers have a higher risk than current smokers, but smoking is not recommended
• NSAIDs may trigger flares

Ulcerative colitis vs Crohn's disease

Diagnosis

• colonoscopy with biopsies: confirms the diagnosis and extent
• stool tests: infections such as C. difficile, and fecal calprotectin for inflammation
• blood tests: blood count, iron, inflammatory markers, albumin, liver function
• imaging in severe flares to check for colon dilation

Irritable bowel syndrome does not cause bleeding or inflammation, which helps distinguish it.

Treatment

The goals are to induce remission, maintain it, heal the lining and prevent complications.

Mild to moderate UC

• 5-aminosalicylates (mesalamine) by mouth and/or as rectal suppositories or enemas. Rectal therapy is very effective for proctitis and left-sided disease
• budesonide for flares in some cases

Moderate to severe UC

• corticosteroids for short-term control of flares, not long-term maintenance
• biologics: anti-TNF agents (infliximab, adalimumab, golimumab), vedolizumab, and IL-12/23 or IL-23 inhibitors (ustekinumab, mirikizumab, risankizumab, guselkumab)
• small molecules: JAK inhibitors (tofacitinib, upadacitinib) and S1P receptor modulators (ozanimod, etrasimod)
• thiopurines (azathioprine) in some patients

Acute severe colitis

Hospital admission with IV steroids, fluids and clot prevention. If there is no response in 3 to 5 days, rescue therapy with infliximab or cyclosporine, or surgery.

Surgery

Removal of the colon and rectum (proctocolectomy), usually with an internal pouch made from the small intestine (ileal pouch-anal anastomosis), cures the colon disease. It is used for severe flares, failure of medicines, or cancer or precancerous changes. Some people develop pouchitis afterward.

Diet and lifestyle

No single diet causes or cures UC. During flares, a low-residue diet may ease symptoms. Eating a balanced diet, staying hydrated, managing stress and avoiding NSAIDs help. Work with a dietitian if weight loss or deficiencies occur.

Complications

• toxic megacolon: dangerous dilation of the colon
• perforation and severe bleeding
• colorectal cancer: risk rises after 8 to 10 years with extensive colitis, so regular surveillance colonoscopies are recommended
• osteoporosis, anemia and blood clots

Outlook

Most people with UC have periods of remission and flares. Modern treatments allow many to achieve long-term remission and a normal life expectancy. Regular follow-up, adherence to maintenance medicines and cancer surveillance improve outcomes.

Frequently asked questions

What are the symptoms of ulcerative colitis?

The main symptoms are diarrhea with blood or mucus, urgency, a frequent feeling of needing to pass stool, cramping belly pain, night-time bowel movements, fatigue and weight loss. Some people also have joint, eye, skin or liver problems.

What triggers an ulcerative colitis flare?

Flares can be triggered by stopping maintenance medicines, infections including C. difficile, NSAIDs such as ibuprofen, antibiotics, and possibly stress. Often no clear trigger is found. Taking medicines as prescribed is the best way to prevent flares.

What is the difference between ulcerative colitis and Crohn's disease?

Both are inflammatory bowel diseases. Ulcerative colitis affects only the colon and rectum, in a continuous pattern affecting the lining. Crohn's disease can affect any part of the gut, in patches, through the full thickness of the bowel wall, and can cause fistulas and strictures.

Can ulcerative colitis be cured?

Medicines cannot cure UC, but they can keep it in remission for long periods. Surgery to remove the colon and rectum cures the bowel disease, though it is a major operation reserved for severe or treatment-resistant cases or cancer risk.

Does ulcerative colitis increase cancer risk?

Yes, especially in people with extensive colitis for more than 8 to 10 years or with primary sclerosing cholangitis. Regular surveillance colonoscopy detects precancerous changes early, and good control of inflammation lowers the risk.