Ulcerative colitis (UC) is a type of inflammatory bowel disease (IBD) in which the lining of the large intestine (colon) becomes inflamed.

The colon then develops ulcers (open sores) that produce blood, pus, and mucus.

The small intestine is rarely affected.

The combination of inflammation and ulcers often causes abdominal discomfort, frequent bowel movements, and bloody stools, according to the Crohn’s and Colitis Foundation.

There are several subtypes of ulcerative colitis, which are named according to the part of the colon affected:

  • Ulcerative proctitis, which affects only the rectum
  • Proctosigmoiditis, which affects the rectum and lower segment of the colon (sigmoid colon)
  • Left-sided colitis, which affects the rectum, sigmoid colon, and descending colon up to the sharp bend near the spleen
  • Pan-ulcerative or total colitis, which affects the entire colon, according to the Mayo Clinic.

How Do I Spot the Signs and Symptoms of Ulcerative Colitis?

The most common symptoms of ulcerative colitis are abdominal pain and diarrhea, which often contains blood or pus.

Symptoms of the disease typically develop gradually and come and go.

Periods without active disease — known as remission — may last for months or even years.

Over time, ulcerative colitis can progress to cover more of the colon. This typically leads to more severe disease and greater symptoms.

If left untreated, UC can also lead to a number of complications, including:

  • Malnutrition
  • Perforated colon
  • Osteoporosis
  • Liver disease
  • Colorectal cancer
  • Toxic megacolon

Learn More About Ulcerative Colitis Symptoms

What Are the Causes and Risk Factors of Ulcerative Colitis?

Ulcerative colitis is believed to be caused by an abnormal response by your body’s immune system.

Your immune system is supposed to defend you against harmful invasive bacteria and viruses. But in some people, the immune system mistakenly attacks the body’s own tissue.

In ulcerative colitis, this may happen when the body mistakes food and helpful bacteria for harmful substances. It may also come about when the body doesn't turn off its response to fighting an infection.

Either way, the immune system sends white blood cells to the lining of the colon, where they cause inflammation and ulcers, according to the Crohn’s and Colitis Foundation.

Experts believe that ulcerative colitis develops because of a combination of environmental factors and genetic predisposition.

While a specific cause is unknown, diet and stress may aggravate the condition, according to the Mayo Clinic.
For example, one study published in April 2021 in Frontiers in Immunology found that a high intake of trans fats — found in many processed foods — increases intestinal inflammation.
A high intake of omega-3 fatty acids may lower the risk of the condition, according to a review published in February 2021 in Frontiers in Immunology.

Fatty cold-water fish — such as mackerel, tuna, salmon, sardines, and herring — are rich sources of omega-3 fatty acids.

How Is Ulcerative Colitis Diagnosed?

To diagnose ulcerative colitis, your doctor will first take a complete medical history and rule out other possible causes of your symptoms.

This will be done with a combination of your history of symptoms, lab tests, imaging scans, and a view of the inside of your colon using a flexible tube and camera (colonoscopy or sigmoidoscopy).

How Is Ulcerative Colitis Treated?

Medications are the main treatment for ulcerative colitis. Other treatment options include dietary changes and surgery, if necessary.

Drugs for ulcerative colitis work by reducing inflammation in your colon.

Some drugs are commonly used for maintenance therapy — to help you stay in remission — while others are used to treat disease activity during flares. You’re likely to need a combination of drugs for optimal treatment.

Surgery may be necessary if your body isn’t responding well to drugs, or if you have severe complications that require urgent treatment.

It’s most common to remove the entire rectum and colon if ulcerative colitis requires surgery, but more conservative approaches may also be considered.

Learn More About Treatment for Ulcerative Colitis

What Should You Eat When You Have Ulcerative Colitis

When it comes to food, there’s no known dietary cause of ulcerative colitis, but different foods may aggravate or help limit symptoms of the disease.

You’re more likely to need to change your diet during periods of active disease (flares), when eating soft, bland foods can help limit symptoms like cramping and diarrhea.

During flares, you may also want to avoid or limit high-fiber and high-fat foods, as well as caffeine, alcohol, dairy products, and spicy foods.

If you’re losing nutrients and water in your diet due to diarrhea, you may need to focus on increasing your fluid intake and getting enough calories, protein, vitamins, and minerals from foods or supplements.

Learn More About Diet and Ulcerative Colitis

Research and Statistics: How Many People Have Ulcerative Colitis?

Ulcerative colitis affects as many as 900,000 Americans, according to the Crohn's and Colitis Foundation.
Symptoms of the condition most often start between ages 15 and 30, with most people diagnosed in their mid-thirties. There’s also a peak between the ages of 50 and 70, according to MedlinePlus.

People of European descent have a higher risk of developing ulcerative colitis than do those of African or Hispanic descent.

People of European Jewish descent have an especially high risk.

Ulcerative colitis tends to run in families, affecting men and women equally overall. But older men are more likely to develop it than older women, according to the Crohn’s and Colitis Foundation.

What Other Conditions Are Related to Ulcerative Colitis

Ulcerative colitis is a type of inflammatory bowel disease (IBD), but it's not the same as irritable bowel syndrome (IBS).

Although the disorders share some of the same symptoms, such as abdominal pain and diarrhea, inflammation and ulcers do not occur with IBS.

Another disease often mentioned alongside ulcerative colitis is Crohn’s disease. Ulcerative colitis and Crohn’s are different types of IBDs that affect the digestive tract in different ways.

There are some common symptoms between the two conditions, but the overall pattern of symptoms tends to be different for each.

While diarrhea and rectal bleeding are more common in ulcerative colitis, Crohn’s disease more often causes severe abdominal pain, nausea, weight loss, and vomiting.

Ulcerative colitis is limited to the lining of the large intestine (colon), whereas Crohn’s disease can affect the entire digestive tract — from your mouth to your anus — and isn’t limited to the inner part of the intestines.

Learn More About the Differences Between UC and Crohn’s

Ulcerative Colitis and COVID-19

The coronavirus pandemic has forced everyone to take extra precautions when it comes to health and safety. This is especially true for individuals with a compromised immune system. Although research shows that people living with UC are no more susceptible to catching the virus than the general population, organizations including the American College of Gastroenterology and the Crohn’s and Colitis Foundation have issued a number of new guidelines to help limit the spread of the infection. It’s also recommended that people with ulcerative colitis get the COVID-19 vaccine.

There are also a number of resources available to help people with UC manage these difficult times — from medication assistance to virtual therapy for mental health.

Learn More About Ulcerative Colitis and COVID-19

Additional reporting by Jordan M. Davidson.

Editorial Sources and Fact-Checking

  • What Is Ulcerative Colitis? Crohn’s & Colitis Foundation.
  • Ulcerative Colitis. Mayo Clinic. July 28, 2017.
  • Ulcerative Colitis. MedlinePlus. August 14, 2015.
  • Ananthakrishnan AN, Khalili H, Konijeti GG, et al. Long-Term Intake of Dietary Fat and Risk of Ulcerative Colitis and Crohn's Disease. Gut. May 2014.
  • Toxic Megacolon. Johns Hopkins Medicine.
  • Colombel JF, Sandborn WJ, Ghosh S, et al. Four-Year Maintenance Treatment With Adalimumab in Patients With Moderately to Severely Active Ulcerative Colitis: Data From ULTRA 1, 2, and 3. American Journal of Gastroenterology. August 2014.


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