Diverticular Disease: Overview and Risk Factors

Diverticula are herniations, or “outpouchings,” of the colon (large intestine) that occur at weak sites in the colon wall.

The development of diverticula appears to be associated with a low–fiber diet. A lack of fiber renders the stool dry and low in bulk, requiring increased pressure by the colon to propel the stool along. Over time, the increased pressure weakens the colon wall and results in the formation of diverticula. In contrast, high fiber intake results in stool that is softer and easier to pass.

Diverticula can result in several disorders:

• Diverticulosis simply means the presence of diverticula. On its own, diverticulosis generally does not cause symptoms and does not require treatment. However, some people do report mild lower abdominal pain, cramping, bloating, constipation, or diarrhea.
  
• Diverticulitis occurs when the diverticula become infected and inflamed, which occurs in 10 to 20 percent of patients. This is a severe disease that requires hospitalization and may necessitate surgical removal of a portion of the colon. Symptoms include fever, severe lower abdominal pain and tenderness, nausea, and vomiting.
  
• Diverticular bleeding occurs when a nearby blood vessel ruptures into the diverticula. This is the most common cause of lower gastrointestinal bleeding in the elderly. It is usually painless, but patients may notice black, tarry stools (melena) or bleeding from the rectum.

Risk Factors

• Advancing age: Diverticula are present in nearly half of Americans by age 60, and more than two–thirds of Americans over age 80 are affected. In contrast, less than 5 percent of people under age 40 are affected.
• Lifestyle: Industrialized countries have a much higher incidence of diverticular disease than developing nations. Some Western nations have prevalence rates that approach 40 percent of the population, whereas developing countries in Asia and Africa have prevalence well below 1 percent. Further, developing nations that adopt a more Western lifestyle (especially a low–fiber diet) have increased rates of diverticulosis.
• Low dietary fiber intake: Several studies have linked low dietary fiber intake to the development of diverticular disease. Further, diverticular disease is much less common in vegetarians, whose diets tend to be much higher in fiber than those of nonvegetarians.
• Total fat and red meat intake: High intake of total fat and red meat has also been correlated with a higher risk for diverticular disease.
• Sedentary lifestyle