Diverticular disease

by Jason Wasserman MD PhD FRCPC
July 24, 2025

Diverticular disease is a common condition in which small pouches called diverticula form in the wall of the colon. These pouches can cause a range of symptoms and complications depending on whether they become inflamed or infected. Diverticular disease includes both diverticulosis, where the pouches are present without inflammation, and diverticulitis, where the pouches become inflamed or infected.

What parts of the digestive tract are affected?

Diverticula can develop anywhere in the colon, but they are most commonly found in the sigmoid colon, the part of the large intestine closest to the rectum. They may also appear in the descending colon on the left side of the abdomen. Less commonly, diverticula may form in the transverse colon, ascending colon, or even in the appendix.

The sigmoid colon is particularly prone to diverticula because of its muscular structure and the high pressure generated when stool is moved through this section. A low-fiber diet and chronic constipation can increase this pressure, making diverticula more likely to form.

What causes diverticular disease?

The exact cause is not completely understood, but several factors are thought to contribute:

  • Low-fiber diet: A lack of dietary fiber can lead to harder stools and constipation, which increases pressure in the colon.

  • Aging: The risk increases with age as the colon wall naturally weakens over time.

  • Chronic straining: Repeated straining during bowel movements may cause the inner lining of the colon to push through weak spots in the muscle wall, forming diverticula.

What are the symptoms?

Many people with diverticular disease, especially those with diverticulosis, have no symptoms at all. When symptoms do occur, they can include:

  • Mild cramping or discomfort in the lower abdomen.

  • Bloating or gas.

  • Constipation or changes in bowel habits.

If the diverticula become inflamed or infected, a condition known as diverticulitis, symptoms can become more severe and may include:

  • Sudden abdominal pain, often on the lower left side.

  • Fever and chills.

  • Nausea or vomiting.

  • Diarrhea or constipation.

  • Loss of appetite.

How is diverticular disease diagnosed?

Doctors typically diagnose diverticular disease using:

  • Medical history and physical exam: Your doctor will ask about symptoms and check your abdomen for tenderness.

  • Imaging tests: A CT scan is commonly used to confirm diverticulitis and check for complications.

  • Colonoscopy: A flexible camera is used to look directly at the inside of the colon. This is helpful for identifying diverticula and ruling out other causes of symptoms.

What does diverticular disease look like under the microscope?

If a tissue sample is taken from the colon and examined under a microscope, pathologists may see the following features:

  • Diverticula: These appear as small outpouchings or sacs that push through the muscle wall of the colon.

  • Diverticulitis: Inflammation around a diverticulum is seen as clusters of immune cells, including neutrophils and lymphocytes, and may include areas of tissue damage or small pockets of infection called microabscesses.

What is diverticulitis?

Diverticulitis is a complication of diverticular disease where one or more diverticula become inflamed or infected. This can cause severe abdominal pain, fever, and changes in bowel function. In most cases, diverticulitis is mild and can be treated with rest, dietary changes, and antibiotics. However, more serious cases may lead to complications and require hospitalization or surgery.

What are the complications of diverticulitis?

Perforation

A perforation is a tear or hole in the wall of a diverticulum. This allows intestinal contents to leak into the abdominal cavity, causing a dangerous infection called peritonitis. Perforation is a medical emergency that usually requires surgery.

Serosal abscess

A serosal abscess is a pocket of pus and inflammatory cells that forms on the outer surface of the colon. It may develop after a perforated or severely inflamed diverticulum. Serosal abscesses are serious and can lead to widespread infection if not treated properly. Treatment may include antibiotics and, in some cases, drainage or surgery.

Questions to ask your doctor

  • Was the inflammation mild or severe?

  • Do I have diverticulosis, diverticulitis, or both?

  • Are there any complications such as a perforation or abscess?

  • Do I need to change my diet or take medications?

  • Will I need another colonoscopy or imaging test?

  • Is surgery recommended or necessary?

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