Colitis is inflammation of the colon (large intestine) that causes symptoms like bloody diarrhea, abdominal pain, and urgent bowel movements. It comes in several forms, from chronic autoimmune conditions that require lifelong management to short-lived infections that clear up on their own. Treatment depends entirely on which type you have and how severe it is.
Types of Colitis
The word “colitis” is an umbrella term. The major forms differ in what triggers the inflammation, where it occurs, and how long it lasts.
Ulcerative colitis (UC) is a chronic inflammatory bowel disease where the immune system attacks the lining of the colon. The inflammation always starts in the rectum and spreads upward in a continuous pattern. It only affects the innermost layer of the colon wall, which distinguishes it from Crohn’s disease. UC is a lifelong condition with periods of flare and remission.
Crohn’s disease can inflame any part of the digestive tract, from the mouth to the anus, and the inflammation goes deeper through the intestinal wall. When Crohn’s primarily affects the colon, it’s sometimes called Crohn’s colitis. Unlike UC, it tends to appear in patches with healthy tissue in between.
Microscopic colitis looks normal during a colonoscopy but shows up under a microscope. It has two subtypes: lymphocytic colitis, where immune cells accumulate in the colon lining, and collagenous colitis, which has that same immune cell buildup plus a thickened band of collagen beneath the surface. Microscopic colitis overwhelmingly affects women (about 72% of cases) and typically appears around age 65. Risk factors include certain medications like NSAIDs, proton pump inhibitors, statins, and SSRIs, as well as autoimmune diseases and celiac disease.
Infectious colitis is caused by bacteria, viruses, or parasites. Salmonella and E. coli are among the most common bacterial culprits. This type usually resolves once the infection is treated or clears on its own.
Ischemic colitis happens when blood flow to part of the colon is temporarily reduced, often in older adults with cardiovascular disease. It typically causes sudden cramping and bloody stool, and most cases resolve without surgery.
Common Symptoms
The hallmark symptoms of colitis are diarrhea (often bloody), abdominal cramping, and an urgent need to use the bathroom. Many people with active colitis wake up at night with diarrhea, which distinguishes it from conditions like irritable bowel syndrome. Unintended weight loss is common during flares.
Chronic forms like ulcerative colitis can also cause problems outside the gut. Joint pain, skin rashes, mouth sores, and eye inflammation all occur. Liver complications, including a condition called primary sclerosing cholangitis, are possible with long-standing disease. These “extra-intestinal” symptoms sometimes appear before the bowel symptoms do.
How Colitis Is Diagnosed
Colonoscopy with tissue biopsy is the gold standard. A doctor threads a flexible camera through the colon to look for visible inflammation, including redness, swelling, loss of the normal blood vessel pattern, and ulcers. In ulcerative colitis, there’s a sharp line where inflamed tissue meets healthy tissue. During the procedure, small tissue samples are taken and examined under a microscope, which is essential for confirming the diagnosis and distinguishing between types. For microscopic colitis, biopsy is the only way to make the diagnosis since the colon looks normal to the naked eye.
If the colon is too inflamed for a full colonoscopy, a flexible sigmoidoscopy (which examines just the lower portion) may be done instead. Blood tests check for anemia and markers of inflammation. Stool samples can detect white blood cells or proteins that signal inflammation and help rule out infections. CT scans or MRI may be used to check for complications like abscesses or perforations.
Treating Mild to Moderate Disease
For mild to moderate ulcerative colitis, the first-line treatment is a class of anti-inflammatory drugs called 5-ASAs (mesalamine is the most common). These can be taken as oral pills, rectal enemas, or suppositories depending on where the inflammation is located. For disease limited to the rectum, a 1-gram daily rectal dose is typically recommended. For more extensive disease, oral doses of at least 2 grams daily are standard. Combining oral and rectal 5-ASA works better than either alone for left-sided disease.
If 5-ASA therapy isn’t enough, a specific type of steroid called budesonide MMX can be added. It’s designed to release medication directly in the colon while minimizing the side effects of traditional steroids. When that still isn’t sufficient, standard oral steroids are used to get flares under control. Steroids are strictly short-term tools for bringing down inflammation. They’re not used for maintenance because of serious side effects with prolonged use, including bone loss and increased infection risk.
Treating Moderate to Severe Disease
When colitis doesn’t respond to first-line therapies, stronger medications that target the immune system come into play. The American Gastroenterological Association recommends several options for moderate to severe UC, including biologic drugs and small molecule therapies.
For patients who haven’t tried biologics before, infliximab or vedolizumab are generally preferred over other options for getting the disease into remission. These are given by IV infusion or injection at scheduled intervals. Other biologics like adalimumab, golimumab, and ustekinumab are also options. A newer class of oral medications called JAK inhibitors, including tofacitinib and upadacitinib, offer an alternative to injections and infusions.
Clinical trial data shows that about 39% of UC patients on these advanced therapies maintain remission, compared to roughly 18% on placebo. Those numbers may sound modest, but they represent people staying symptom-free over months to years. The goal isn’t just controlling symptoms but achieving “mucosal healing,” meaning the inflammation visibly resolves on repeat colonoscopy.
When Surgery Is Needed
Surgery becomes necessary when medications can no longer control the disease or when dangerous complications develop. Emergency surgery is required for a perforated colon, life-threatening bleeding, or toxic megacolon (a rare condition where the colon rapidly dilates and can rupture). Urgent surgery may be needed for severe flares that don’t respond to intensive medical treatment in the hospital.
Elective surgery is considered for people with persistent symptoms despite trying multiple medications, those with precancerous changes found on biopsy, or those with long-standing disease and elevated cancer risk. The most common procedure is removing the entire colon and rectum, then creating an internal pouch from the small intestine that connects to the anus. This “J-pouch” surgery eliminates ulcerative colitis permanently (since there’s no colon left to be inflamed) while allowing relatively normal bowel function. Other options include creating a permanent external pouch (ileostomy) or, less commonly, removing the colon but leaving the rectum in place.
Diet During Flares and Remission
There’s no single diet proven to treat colitis, and the Crohn’s & Colitis Foundation specifically warns against following restrictive diets without professional guidance. Self-imposed food restrictions can lead to nutrient deficiencies, unintended weight loss, malnutrition, and even disordered eating, all of which can worsen disease outcomes.
If you’re in remission but still have digestive symptoms, working with a dietitian who specializes in inflammatory bowel disease is the most productive step. They may suggest a low-FODMAP diet to identify specific trigger foods. During active flares, many people find that softer, lower-fiber foods are easier to tolerate, but this varies widely from person to person.
Long-Term Cancer Screening
Chronic colitis increases the risk of colorectal cancer, particularly in ulcerative colitis and Crohn’s disease affecting the colon. Screening colonoscopy is recommended 8 to 10 years after symptoms first appeared. After that initial screen, surveillance colonoscopies should happen every 1 to 3 years depending on findings. Once the disease has been present for 20 years, the interval tightens to every 1 to 2 years. Patients with primary sclerosing cholangitis, a liver condition linked to UC, need yearly surveillance colonoscopies because their cancer risk is higher. People whose colitis is limited to the very lowest part of the colon (proctosigmoiditis) don’t face significantly elevated cancer risk and can follow standard screening guidelines for the general population.