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.

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
  • fever
  • 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.


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
  • broth
  • ice pops
  • water
  • gelatin
  • 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
  • smoking
  • 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

Some studies have indicated that genetics may be a factor.


Diagnosing diverticular and diverticular-related diseases can be challenging, and there are a number of tests that might be carried out to ensure correct diagnosis.

There are several illnesses and conditions with similar symptoms, such as irritable bowel syndrome (IBS), so diagnosis of diverticular disease is not easy.

A doctor can rule out other conditions by having some blood tests done. They may also use the following techniques:

Colonoscopy: The doctor has a look inside the colon using a thin tube with a camera at the end called a colonoscope. The colonoscope enters through the rectum. Hours or a day before the procedure begins, people are given a laxative to clear their bowels.

A local anesthetic is given before the procedure starts. This test is not usually done during an acute episode of diverticulitis, but done around 6 weeks after resolution to ensure there are no signs of cancer.

Barium enema X-ray: A tube is inserted into the rectum, and a barium liquid is squirted into the tube and up the rectum. Barium is a liquid that shows up in X-rays. When organs that do not normally show up on an X-ray are coated with barium, they become visible. The procedure is not painful.

Diagnosing diverticulitis

If an individual has a history of diverticular disease, the doctor will be able to diagnose diverticulitis by carrying out a physical examination and asking some questions about symptoms and their medical history.

A blood test is useful because if it reveals a high number of white blood cells, it probably means there is an infection. However, many people without a high number of white blood cells may still have diverticulitis.

People who have no history of diverticular disease will need additional tests. Other conditions can have similar symptoms, such as a hernia or gallstones.

A computer tomography (CT) scan may be used and is often the most helpful. A barium enema X-ray may also be useful. If symptoms are severe, the CT scan may tell whether the infection has spread to another part of the body, or whether there is an abscess.

Individuals can often self-treat if the case is not too severe.

Diverticulosis treatment

Most people can self-treat their diverticular disease if it is mild, mainly with the help of painkillers and by consuming more dietary fiber.

Painkillers such as aspirin or ibuprofen should be avoided as they increase the risk of internal bleeding, and may also upset the stomach. Acetaminophen is recommended for pain relief from diverticular disease.

Eating more dietary fiber, which includes fruits and vegetables, will help resolve the symptoms by softening stool and helping stool patterns become more regular. This may sometimes take a few weeks.

Bulk-forming laxatives may help those who have constipation. It is important to drink plenty of fluids with these medications.

People who experience heavy or constant rectal bleeding should see their doctor.

Diverticulitis treatment

Mild cases of diverticulitis can generally be treated by the individual. However, a doctor may prescribe antibiotics, as well as acetaminophen for the pain.

It is important to complete the whole course of antibiotics, even if symptoms get better.

Some people may experience drowsiness, nausea, diarrhea, and vomiting while they are taking their antibiotics.

For those on the contraceptive pill, it is important to remember that antibiotics can interfere with its effectiveness. This effect on the contraceptive pill continues for about 7 days after stopping the antibiotic, so another form of contraception should overlap with this time.

Hospital treatment may be necessary if any of the following apply:

  • Normal painkillers do not alleviate the pain, or the pain is severe.
  • The individual cannot consume enough liquids to keep hydrated.
  • The person with diverticulitis cannot take oral antibiotics.
  • They have a poor state of health.
  • The doctor suspects complications, often if the immune system is weak.
  • Treatment at home is ineffective after 2 days.

Hospital patients are generally given antibiotics intravenously (IV), as well as fluids if they are dehydrated.


People who have at least two diverticulitis episodes may benefit from surgery. Studies indicate that such patients are significantly more likely to have further episodes and complications if they do not have surgery.

A colon resection removes part of the affected colon and joins the remaining healthy parts together.

Patients who undergo colon resection will have to introduce solid foods into their system gradually. Apart from this, their normal bowel functions will not usually be affected. A small study suggests that chewing gum after colon surgery may accelerate the return of normal bowel function and shorten hospital stays.


Peritonitis: Infection may spread into the lining of the abdomen if one of the infected diverticula bursts. Peritonitis is serious and can sometimes be fatal. It requires immediate antibiotic treatment. Some cases of peritonitis require surgery.

Abscess: This is a pus-filled cavity that requires antibiotics. Sometimes, surgery is required to get the pus out.

Fistula: These are abnormal tunnels, or tubes, that connect two parts of the body, such as the intestine to the abdominal wall or the bladder. A fistula can be formed after infected tissues touch each other and stick together; when the infection is over, a fistula forms. Often, surgery is needed to get rid of a fistula.

Intestinal obstruction: The colon may become partly or totally blocked if infection has caused scarring. If the colon is blocked completely, emergency medical intervention is needed. Total blockage will lead to peritonitis. If the colon is partially blocked, they will need treatment. However, it is not as urgent as total blockage.

Depending on the degree of scarring and the extent of blockage, a colon resection may be needed. Sometimes, a colostomy may be required. A hole is made on the side of the abdomen, and the colon is redirected through the hole and connected to an external colostomy bag.

Once the colon heals, it is rejoined. In rare cases, the doctors may have to create an internal ileoanal pouch.


People who eat a well-balanced diet with plenty of fruit and vegetables have a lower risk of developing diverticulitis.

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