Understanding Diverticulitis and How Common It Is

Diverticulitis occurs when small, bulging pouches called diverticula that form in the wall of the large intestine become inflamed. These pouches are quite common, especially as people get older. The simple presence of these pouches without any symptoms is called diverticulosis. Most people who have diverticula never experience any problems with them and may not even know they exist unless discovered during an unrelated medical exam^[1].

The condition is remarkably widespread in developed countries. More than 30% of adults in the United States between ages 50 and 59 have diverticulosis, and this number climbs to more than 70% in those older than 80^[3]. However, only a small fraction of people with diverticula will develop diverticulitis. Less than 5% of people with diverticulosis go on to develop the inflamed or infected form of the condition^[3].

When inflammation does occur, it affects approximately 4% of people who have diverticulosis. Once someone has experienced diverticulitis, there is a 20% chance of experiencing it again^[2]. In the United States alone, about 200,000 people are hospitalized for diverticulitis each year, with around 71,000 additional hospitalizations for diverticular bleeding^[3].

Who Is More Likely to Develop Diverticulitis

Age is the most significant factor in developing both diverticulosis and diverticulitis. The older you get, the more likely you are to develop these small pouches in your colon wall. While the condition can occur in younger people, it becomes increasingly common after age 50^[1].

Gender also plays a role, though this changes with age. Among people younger than 50, diverticulitis is more common in men than in women. However, this pattern reverses after age 50, when diverticulitis becomes more common in women^[3].

Race and ethnicity appear to influence both the likelihood and location of the condition. Research suggests that in the United States, diverticulitis is more common in white Americans than in other groups, while diverticular bleeding is more common in Black Americans^[3]. Interestingly, people of Asian descent tend to develop diverticula in a different part of the colon than people of European descent. In Asian populations, diverticula typically form in the first part of the colon (the ascending colon), which is in the upper right area of the abdomen, rather than in the lower left side where they usually appear in Western populations^[2].

What Causes These Pouches to Form

Researchers are not entirely certain what causes diverticula to form in the first place. The leading theory suggests that increased pressure within the colon pushes the inner lining of the intestine out through weak spots in the colon wall, creating these small bulging pouches^[16]. This happens most commonly in the lower part of the colon, called the sigmoid colon, which is the last section before the rectum^[1].

Diet appears to play a significant role in the development of diverticular disease. The condition became much more common in Western countries during the 20th century, and it remains relatively uncommon in African and Asian nations where traditional high-fiber diets are still common^[15]. Studies have shown that vegetarians develop diverticulosis less frequently than people who eat typical Western diets^[15].

The type of fiber may matter as well. Large-scale studies have found that people with higher overall fiber intake, particularly from grains, cereals, and fruits, have a lower incidence of diverticulitis. Interestingly, vegetable intake may not provide the same protective benefit^[15].

Once the pouches have formed, inflammation and infection can develop for several reasons. Diverticula can trap small amounts of stool or bacteria, creating an environment where infection can flourish. Sometimes a tear in the lining of a pouch allows bacteria to enter, or the pouch itself may rupture. It is not always clear whether infection or a tear comes first, but both often involve inflammation that leads to the symptoms of diverticulitis^[2].

Risk Factors That Increase Your Chances

Several lifestyle factors and health conditions increase the risk of developing both diverticulosis and diverticulitis. Diet is one of the most important modifiable risk factors. Diets that are low in fiber and high in red meat have been associated with an increased risk of developing diverticular disease^[4].

Physical inactivity is another significant risk factor. Lack of regular exercise has been linked to a higher likelihood of developing diverticular complications. On the other hand, vigorous physical activity such as jogging, swimming laps, or playing tennis or basketball is associated with a reduced risk of both diverticulitis and diverticular bleeding^[16].

Obesity increases the risk of diverticular disease. Maintaining a healthy weight appears to be protective, while being significantly overweight puts additional stress on the digestive system^[4]. Smoking is another modifiable risk factor that increases the likelihood of developing complications from diverticular disease^[16].

Certain medications may also play a role. Taking nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or aspirin, as well as steroids, has been associated with an increased risk of developing diverticular problems. These medications can irritate the digestive tract and may increase the likelihood of complications^[4].

There may also be genetic factors at work. Studies of families with multiple cases of diverticulitis have identified at least two genes associated with the condition. One gene called TNFSF15 has been shown in multiple studies to be linked with diverticulitis^[15]. This genetic component may explain why some people develop problems while others with similar lifestyles do not.

Recognizing the Symptoms

Most people with diverticulosis have no symptoms at all and are unaware they have the condition. It is usually discovered incidentally during a colonoscopy or imaging test done for another reason^[1]. However, some people with diverticula may experience chronic symptoms such as bloating, cramping or pain in the lower abdomen, constipation, or diarrhea^[4].

When diverticula become inflamed or infected, causing diverticulitis, symptoms are typically much more noticeable and can be quite severe. The most common symptom is pain in the abdomen. For most people of European descent, this pain is located in the lower left side of the abdomen because diverticula most commonly form in the sigmoid colon, which sits in that area^[1]. However, people of Asian descent may experience pain in the upper right area of the abdomen since their diverticula tend to form in a different part of the colon^[2].

The pain can vary in how it develops and feels. Sometimes it comes on suddenly and is intense from the start. Other times it may be mild at first and gradually worsen over several days. The pain may feel sharp and penetrating, or it might have a burning quality. Regardless of how it starts, the pain is usually moderate to severe and can be pinpointed to a specific spot^[2].

Beyond abdominal pain, people with diverticulitis often experience fever, which indicates that infection is present. Nausea and vomiting are also common, along with changes in bowel habits. Some people develop constipation, while others experience diarrhea^[2]. The abdomen may become distended or swollen, and you might be able to feel areas of tenderness when pressing gently on the belly^[2].

Some people may notice blood or mucus in their stool. Diverticular bleeding can occur when a small blood vessel in a pouch ruptures. This bleeding can range from minor to severe and life-threatening^[3]. Other symptoms can include lack of appetite and general feelings of being unwell^[6].

Preventing Diverticulitis

While there is no guaranteed way to prevent diverticulosis from developing, especially as you age, there are several lifestyle changes that can reduce the risk of developing diverticulitis if you already have diverticula. These same strategies can help prevent flare-ups if you have already experienced diverticulitis^[5].

Eating a healthy, balanced diet that includes plenty of fiber is one of the most important preventive measures. A diet rich in whole grains, fruits, and vegetables provides the fiber needed to keep stools soft and reduce pressure in the colon. Good sources of fiber include bran, whole-wheat pasta, apples, pears, raspberries, beans, sweet potatoes, and avocados^[17]. If you are not used to eating much fiber, it is important to increase your intake gradually and drink plenty of water. Adding too much fiber too quickly can cause gas and bloating that might actually irritate the gut^[5].

Staying physically active is another key prevention strategy. Regular exercise helps strengthen the muscles of the intestines, making it easier to pass stool comfortably and regularly. If you have not been active recently, start with a regular walk and work your way up to 30 minutes of activity most days. Gradually add more intensity and variety, including both cardiovascular exercise and resistance training^[5].

Maintaining a healthy weight is important. Obesity is associated with diverticular complications, so keeping weight in a healthy range through diet and exercise can be protective^[16]. If you smoke, quitting is crucial. Smoking increases the risk of developing diverticular disease and its complications^[5].

Avoiding certain medications when possible may also help. NSAIDs such as ibuprofen can cause stomach problems and may increase the risk of perforation in the bowel. If you need pain relief, consider alternatives like acetaminophen (paracetamol). Similarly, opioid painkillers such as codeine can cause constipation, which may worsen diverticular problems^[5].

Drinking plenty of water throughout the day helps keep stools soft and regular. This reduces the pressure within the colon and makes bowel movements more comfortable. When you feel the urge to have a bowel movement, do not delay or try to hold it in. Allowing stool to remain in the colon longer than necessary can contribute to constipation and increase pressure on diverticula^[21].

How the Body Changes with Diverticulitis

Understanding what happens in the body during diverticulitis helps explain both the symptoms and the potential complications. The large intestine normally has a smooth inner wall. When diverticula form, the inner lining of the intestine pushes through weak spots in the muscular wall, creating small pouches that bulge outward. These pouches are typically found in the lower part of the colon, though their location can vary by ethnicity^[1].

When one or more of these pouches becomes inflamed, the body responds with increased blood flow to the area. This is part of the immune system response, which delivers disease-fighting cells and fluids to combat infection or injury. This increased activity causes swelling, redness, and pain in the affected area^[1].

Inflammation in diverticula often involves both a tear in the lining of the pouch and bacterial infection. The tear may occur first, allowing bacteria that normally live in the colon to invade the tissue, or bacteria may multiply within a pouch first, causing enough pressure and damage to create a tear. Either way, the result is inflammation that can range from mild to severe^[2].

In uncomplicated diverticulitis, the inflammation remains localized to the affected pouch and surrounding tissue. The immune system fights the infection, and with rest and possibly antibiotics, the inflammation resolves. The tissue heals, and normal function returns^[2].

However, in complicated diverticulitis, the inflammation causes additional problems. Severe inflammation may cause a diverticulum to rupture completely, spilling intestinal contents into the abdominal cavity. This can lead to peritonitis, a serious infection of the lining of the abdominal cavity^[4].

Sometimes pus accumulates in a pocket called an abscess. This painful collection of infected fluid forms near the inflamed diverticulum and may require drainage. Chronic or repeated inflammation can cause scar tissue to form, which may narrow the colon and create a stricture that makes it difficult for stool to pass. In severe cases, this can lead to a partial or complete blockage called an obstruction^[4].

Another possible complication is a fistula, which is an abnormal tunnel that forms between the colon and another organ or structure. This might connect the colon to the bladder, vagina, or another part of the intestines. Fistulas allow bacteria and intestinal contents to reach places they should not be, causing additional infections and problems^[4].

Diverticular bleeding occurs through a different mechanism. A small blood vessel in the wall of a diverticulum can rupture, sometimes without any inflammation present. This bleeding can be minor and stop on its own, or it can be severe enough to require emergency treatment and blood transfusions^[16].

Chronic inflammation from repeated episodes of diverticulitis can lead to permanent changes in the colon. Scar tissue may accumulate, the colon wall may thicken, and the normal muscular contractions that move stool along may become less effective. This is why some people develop chronic diverticulitis with ongoing symptoms even between acute flare-ups^[2].