What Causes Diverticulitis?

Medically reviewed by Jay N. Yepuri, MD

Diverticulitis is a digestive condition that occurs when small pouches along the walls of your intestine become infected or inflamed. These pouches (diverticula) develop over time when weak spots in the intestinal walls push outward, forming little pouches or sacs. The formation of diverticula is called diverticulosis, which is common in older adults.

By age 60, about half of all adults have diverticulosis. Researchers aren’t sure exactly what causes diverticulosis, but certain factors, including genetics, age, lifestyle habits, and underlying health conditions, likely play a role.

Most people with diverticulosis do not have symptoms, and many are unaware they have it because it usually doesn’t cause problems. But if one of the pouches tears and becomes inflamed or infected (diverticulitis), symptoms like abdominal pain and cramping can come on suddenly, often worsening over several days.

Fewer than 5% of people with diverticulosis will develop diverticulitis. Once you’ve had diverticulitis, there’s a 13% chance you may develop it again. Understanding the possible causes and risk factors for diverticulitis may help reduce your risk of developing the condition.

Theories

When you have diverticulosis, tiny tears can develop in the pouches (diverticula) lining the intestines. The diverticula can become inflamed or infected when this happens, leading to diverticulitis. What causes these tears and diverticulitis is unclear, but researchers have a few theories.

Trapped Stool or Bacteria

One theory suggests that diverticulitis develops when bacteria or stool become trapped within the diverticula (small pouches) that form along the intestinal wall. The diverticula provide an ideal environment for bacteria to thrive, which can lead to a bacterial infection and symptoms of leading diverticulitis (e.g., abdominal pain, cramping, fever).

Microbiome Changes

Your gut microbiome is a community of trillions of microorganisms, including bacteria, viruses, and fungi, that live in your intestines. When your gut microbiome is balanced, these microorganisms work together to support your digestive system and overall health. Disruptions in the balance of your gut microbiome can occur due to dietary changes or antibiotic use, which may lead to changes in digestive health and cause diverticulitis.

Chronic Inflammation

Inflammation is the body’s natural response to injury or infection. In the short term, inflammation is beneficial, helping your body fight off germs and heal from injuries. When your immune system continues to produce inflammatory cells and chemicals long after the injury has healed or germs have been fought off, it can lead to chronic inflammation and increase your risk of health problems.

Some research suggests that diverticulitis may develop due to chronic inflammation in the colon (large intestine). Factors like diet and underlying autoimmune conditions are linked to chronic inflammation and may contribute to the development of diverticulitis.

Is Diverticulitis Hereditary?

Research from 2019 and 2020 shows that diverticulosis and diverticulitis (diverticular disease) are hereditary. This means having a close family member like a parent or sibling with diverticular disease may increase your risk of developing the condition.

In twin and family studies, researchers discovered specific genes associated with diverticular disease: ARHGAP15, COLQ, and FAM155A. These genes play a role in your body’s immune and inflammatory response. Variants in the FAM155A gene are linked to an increased risk of diverticulitis.

Researchers estimate that around 40-50% of the risk for diverticular disease is genetic. Having a genetic predisposition for diverticulitis does not mean you will develop it. Genetic, lifestyle, and environmental factors combined likely contribute to its development.

Who Gets Diverticulitis?

About 5% of people with diverticulosis will develop diverticulitis. Diverticulitis is most common in adults over 60, and the risk increases with age. Other factors associated with an increased risk of diverticulitis include:

• Sex: In people younger than 50, diverticulitis is more common in people assigned male at birth. In people 50 and older, it is more common in people assigned female at birth.

• Ethnicity: Diverticulitis is more common in White Americans than Black or Latinx Americans.

Risk Factors

Certain lifestyle and environmental factors are associated with an increased risk of diverticulitis.

Low-Fiber Diet

A diet low in fiber, high in red meat, and lacking in fruits and vegetables can increase your risk of diverticulitis. Fiber helps stool move smoothly through the intestines. Without enough fiber, poop can become hard and difficult to pass, putting extra pressure on the intestines, which may cause diverticula to form. People who eat a high-fiber diet are 41% less likely to develop diverticulitis than those with low fiber intake.

Related: Is Your Stool Healthy? Check Out the Bristol Stool Chart

Smoking

Smoking cigarettes increases the risk of diverticulitis. Smoking contributes to inflammation, which may impact intestinal health. Research shows that nicotine in cigarettes reduces the tone and activity of muscles in the intestines, which may contribute to smokers’ increased risk of diverticulitis. 

Related: What You Need to Know About Quitting Smoking

Obesity

Diverticulitis is more common in people with obesity (BMI of 30.0 or higher). Extra body weight can lead to chronic, body-wide inflammation and gut microbiome changes, which may help explain why obesity increases the risk of diverticulitis.

Medications

Several medications, including nonsteroidal anti-inflammatory drugs (NSAIDs), opioids, and corticosteroids, increase the risk of diverticulitis. These drugs increase the chances of perforations in the bowel, causing diverticular bleeding.

Lack of Exercise

Lack of physical activity increases the risk of diverticulitis. Regular exercise may lower the risk of diverticulitis by 25%.

Other Health Conditions

Studies show that high blood pressure (hypertension) and immunodeficiency disorders such as kidney disease are associated with a higher risk of diverticulitis.

Geography

Diverticulitis is more common in Western countries, where low-fiber, high-sugar diets are more common. Parts of the world where fiber-rich diets are commonplace have lower rates of diverticulitis.

A Quick Review

Diverticulitis is a digestive condition that develops when the small pouches (diverticula) that form along the intestinal walls become infected or inflamed. Though researchers have not identified the exact cause of diverticulitis, studies suggest a combination of genetic, lifestyle, and environmental factors likely play a role. 

Rates of diverticulitis are higher in Western countries where more low-fiber, high-sugar diets are common. Aging, lack of physical activity, prolonged use of certain medications (e.g., NSAIDs, opioids), and smoking are associated with an increased risk of diverticulitis. 

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