Diverticulitis: Causes, symptoms, and treatments

Diverticulitis occurs when pouches begin to protrude outward from the wall of the colon, becoming infected and inflamed.

However, these pouches can protrude without becoming infected. This is known as diverticulosis, and the pouches are called diverticula. Many individuals have a number of diverticula but feel no ill effects. However, when a pouch becomes infected, it can be very painful.

Around 50 percent of people are thought to have diverticulosis by the age of 50 years. An estimated 10 to 25 percent of people with diverticulosis will go on to develop diverticulitis, although this figure is debated, and some believe it may be as low as 1 percent.

By the age of 80 years, an estimated 65 percent of people have diverticulosis.

A study found that the incidence of diverticulitis among young obese adults is growing. A National Institutes of Health (NIH) report revealed that the cost of digestive diseases is now more than $141 billion a year in the United States.

This MNT Knowledge Center article will look at the causes, symptoms, risk factors, and treatments of diverticulitis and related conditions. We will also discuss the diverticulitis diet.

Fast facts on diverticulitis

Here are some key points about diverticulitis. More detail and supporting information is in the main article.

Diverticulitis is an infected pouch in the colon.

Symptoms of diverticulitis include pain, constipation, and blood in the stool.

One of the main causes of diverticular disease is thought to be a lack of dietary fiber.

Most people can self-treat the condition.

Surgery for diverticulitis may be necessary if the condition is recurring.


Diverticulitis diverticulosis diagram

The symptoms of diverticulosis and diverticulitis are different.

Diverticulosis symptoms

The majority of people with diverticulosis will never experience any symptoms. This is called asymptomatic diverticulosis.

There may be episodes of pain in the lower abdomen. More specifically, usually in the lower left side of the abdomen. The pain often comes when the individual eats or passes stools. There may be some relief after breaking wind.

Other symptoms include:

changing bowel habits

constipation and, less commonly, diarrhea

small amounts of blood in stools

Diverticulitis symptoms

When diverticulitis becomes inflamed, symptoms include:

constant and usually severe pain, usually on the left side of the abdomen although occasionally on the right


more frequent urination

painful urination

nausea and vomiting

bleeding from the rectum


It is unknown why pouches start to protrude outward from the colon. However, a lack of dietary fiber is often thought to be the main cause.

Fiber helps to soften stools, and not consuming enough dietary fiber leads to hard stools. This may cause more pressure or strain on the colon as muscles push the stool down. This pressure is thought to cause the development of diverticula.

Diverticula occur when weak spots in the outside layer of colon muscle give way and the inner layer squeezes through.

Although there is no clear clinical evidence proving a link between dietary fiber and diverticulosis, researchers claim that the circumstantial evidence is convincing. However, the topic is hotly debated.

In parts of the world where dietary fiber intake is large, such as in Africa or South Asia, diverticula disease is fairly uncommon. On the other hand, it is quite common in Western countries where dietary fiber intake is much lower.

However, other reports have debunked the link between increased dietary fiber and diverticulitis prevention, advising that it may actually increase the likelihood of the disease.

Previously, the consumption of nuts, seeds, and corn was thought to be a cause of diverticula development, but a study in 2008 found no link.

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Sometimes, a doctor will recommend that someone with diverticulitis goes on a special diet, to give the digestive system an opportunity to rest.

Initially, only clear liquids are allowed for a few days. These include:

ice chips

fruit juice without pulp


ice pops



tea and coffee without cream

As symptoms ease, a person with diverticulitis can start to include low-fiber foods, including:

canned or cooked fruits and skinned, seedless vegetables

low-fiber cereals

eggs, poultry, and fish

milk, yogurt, and cheese

refined white bread

pasta, white rice, and noodles

Foods to avoid

Gastrointestinal problems often come with a list of foods to avoid. It has been suggested in the past that nuts, popcorn, and seeds can cause symptoms to flare up.

However, as the causes of diverticulitis are not known, the National Institutes of Health advise that there are no particular foods to exclude from the diet that will improve diverticulitis symptoms.

The high-fat, low-fiber diet that characterizes Western eating has been shown to increase the risk of diverticulitis in a recent study. It is best, therefore, not to eat red meat, deep-fried foods, full-fat dairy, and refined grains.

Food should be excluded based on individual experience. If you find that a particular type of food aggravates the effects of diverticulitis, avoid it.

Risk factors

It is not fully understand why diverticulitis occurs. Bacteria in the stool may rapidly multiply and spread and cause the infection. It is thought that a diverticulum might become blocked, possibly by a piece of stool, which then leads to infection.

Risk factors include:

age, as older adults have a higher risk than younger individuals.

being obese


lack of exercise

a diet high in animal fats and low in fiber

some medications, including steroids, opiates, and non-steroidal anti-inflammatories (NSAIDs), such as ibuprofen

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