Ulcerative Colitis vs. Diverticulitis: What’s the Difference?

Medically Reviewed by Sabrina Felson, MD on May 26, 2022
7 min read

If you’ve had stomach pain for a while and see blood when you poop, you might have ulcerative colitis (UC) or diverticulitis. The two conditions are different, but some of their symptoms can be the same because they’re both conditions in the large intestine or colon.

UC is a type of inflammatory bowel disease (IBD) that irritates the lining in your large intestine (also known as the colon). This causes tiny open sores, called ulcers, that produce pus and mucous.

Diverticulitis is a condition that you have when one or more tiny, bulging pouches (called diverticula) form over weak spots in the colon wall, and then tear and become infected or inflamed. Diverticula are usually pea-sized and can form anywhere throughout the colon. But they’re commonly found in the lower-left side of your large intestine called the sigmoid colon.

UC and diverticulitis both start out in the large intestine and share symptoms like belly pain and bloody poop. Both conditions are more likely the older you get, and both can range from mild to severe and vary for each person. But they differ in terms of what causes them and how your doctor might treat them.

UC is a lifelong condition that can lead to life-threatening problems. About a million Americans are affected by it. It can affect people at any age, including those in their 20s and 30s. If you have UC, you also might have weight loss or arthritis.

Diverticulitis, not a lifelong condition, is a complication of “diverticulosis.” It’s the term doctors use when one or more of the small bulging sacs grow on your colon wall. It usually starts in middle age and it’s common in older people. Diverticulitis can happen to you once and never happen again, or it might come and go. About 50% of those over the age of 60 have it, and almost everyone above 80 has it, too. Most are mild cases that don’t cause any symptoms and aren’t reasons to worry. Up to 30% of the people with diverticulosis go on to have diverticulitis. And among them, anywhere between 5%-15% will have symptoms like bloody poop.

UC and diverticulitis have some of the same symptoms, but they also have some that are different.

Shared ones include:

If you have one or more of these symptoms, talk to your doctor. UC symptoms also include:

  • Urgency to poop
  • Trouble pooping despite the urgency
  • Weight loss
  • Fatigue
  • Lack of growth in children

Diverticulitis symptoms also include:

It’s important to note that if you have diverticulitis, you’re more likely to have constipation than diarrhea.

Doctors aren’t sure what causes you to get UC or diverticulitis, but the two conditions have some common risk factors:

  • Age. Your odds for either condition go up as you get older.
  • Race. White people are more likely than those of any other race to have UC or diverticulitis.

UC might be caused by an abnormal immune response in your body. This means that if your immune system is fighting off a virus or bacteria, it may mistakenly attack cells in your digestive tract, too.

Genes might also play a role. If a close relative like your parent or sibling has UC, you’re more likely to have it, too. If you're of Ashkenazi Jewish descent (ancestors came from Eastern or Central Europe), your risk is even higher. Diet and stress don’t cause UC, but they may trigger your symptoms and cause flare-ups.

As for what causes diverticulitis, experts believe bacteria found in your poop might get pushed into the bulging sacs as it passes through the colon. This causes the sacs to become infected or inflamed. Another theory is that your poop, especially if you’re constipated, might put a lot of pressure against the colon walls as it passes through. This can cause tears in the sacs and increase your chances of an infection.

Other risk factors for diverticulitis include:

  • Obesity
  • Smoking
  • Lack of exercise
  • Diet low in fiber and high in animal fat
  • Certain medications (like steroids, opioids, and nonsteroidal anti-inflammatory drugs like ibuprofen)

If you think you have either UC or diverticulitis, talk to your doctor about it. You might be referred to a gastroenterologist, a doctor who specializes in digestive issues, for a correct diagnosis.

Your doctor will first do a detailed medical exam. They’ll ask you about your medical history including things like your diet, your bowel movements, and medications you might be taking.

Common tests to diagnose UC and diverticulitis include:

  • Blood tests. This is done to check for infections
  • Stool sample test. This checks for bacteria or parasites that might cause your stomach pain, cramps, or diarrhea
  • Colonoscopy. The doctor will use a thin, flexible tube with a camera on the tip to explore your entire colon. They may take small tissue samples to test.
  • Flexible sigmoidoscopy. This is similar to a colonoscopy, except your doctor will only explore your rectum and s-shaped sigmoid colon – both of which are located at the lower end of your colon. This is usually done if you have severe inflammation.
  • Barium enema. This test is also called lower gastrointestinal tract radiography. In this test, your doctor injects a liquid containing barium into your butt. The barium coats your entire colon and makes it easier to see clearly under an X-ray scan.
  • CT scan. This test allows your doctor to scan your abdomen and pelvic area and spot inflamed areas in your colon. The scan can detect the irritated or inflamed pouches for diverticulitis and confirm the condition.

In both conditions, treatments usually involve medications or, sometimes, surgery. In severe cases, your doctor may recommend a combination of the two to bring your symptoms under control. Certain over-the-counter medications may ease some of your pain-related symptoms. These include:

  • Anti-diarrheal medications
  • Pain relievers
  • Antispasmodics to ease cramps and bloating
  • Iron supplements, especially if you’re bleeding

UC treatments may include:

Anti-inflammatory drugs. This is usually the first line of treatment. This can include drugs like 5-aminosalicylates and corticosteroids. Some newer drugs like sulfasalazine and 5-ASAs (like mesalamine), which are called “steroid-sparing,” can be safely taken long-term. Your doctor may not want you to take steroids long-term because of their side effects.

Immunosuppressant drugs. This helps to reduce inflammation in your colon and cut down the immune response that might attack your digestive cells.

Biologics. This targets the proteins made by your immune system.

Surgery. About 30% of people who have UC need surgery. It’s sometimes the only cure, especially if medications don’t ease your symptoms or they become too difficult to manage. Your doctor may consider a surgery called proctocolectomy.

In this procedure, your entire colon and rectum are removed. Most surgeries also involve a procedure in which your doctor will attach a pouch at the end of the small intestine or outside your body to pass poop directly into it.

Diverticulitis treatments may include:

Antibiotics. If your case is mild, your doctor may prescribe oral antibiotics to bring the symptoms under control. If you have multiple bouts of diverticulitis episodes, you’ll need to go to the hospital for intravenous (IV) antibiotics and fluids. At this point, your doctor may consider surgery as an option, too.

Surgery. Your doctor may recommend you have surgery for diverticulitis because of issues in your colon such as:

  • Abscess (a type of walled-off infection)
  • Obstruction
  • Tears that cause pus or poop to leak into your stomach cavity
  • Tunnel-like opening in the colon that connects with other organs (fistula)
  • Continuous bleeding (if your diverticulitis is recurring)

In some cases, you may need a colostomy bag after surgery. It’s a pouch that’s attached outside of your body to pass poop into if your colon needs time to heal. Once your colon is healthy, your doctor might remove the colostomy bag.

UC is a lifelong condition, and your symptoms may come and go. About 30% of people with UC have severe symptoms, and flare-ups might happen more frequently. While medications often help, surgery may also be needed.

In contrast, most cases of diverticulitis, even though it’s also considered a lifelong condition, clear up with a 7- to 10-day course of antibiotics and plenty of rest. If you have severe symptoms, talk to your doctor about other treatment options.

Managing your diet and stress and making time for regular physical exercise are key to lowering your risks for both conditions. However, because some of the symptoms are specific, there are steps you can take to avoid your condition flaring up or getting worse.

To prevent diverticulitis, you should:

  • Eat more fiber. This helps your poop move better in your digestive tract and reduces any pressure on the colon walls
  • Drink lots of water, this prevents constipation.

If you’re not sure what to eat, talk to your doctor.

To lower your odds for UC or manage flare-ups, you should:

  • Get plenty of sleep. This can ease emotional stress and keep your immune system in check.
  • Avoid using too many nonsteroidal anti-inflammatory drugs (NSAIDs). For pain relief and fever, switch to alternatives like acetaminophen (Tylenol).
  • Be careful when you take antibiotics. These drugs can trigger UC flare-ups. Let your doctor know if it does.