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

Diverticular Disease: Diagnosis and Treatment

Diagnosis

History and physical examination and blood testing are the initial steps. They cannot make the diagnosis, but they may raise suspicion. In particular, the combination of left lower abdominal pain, fever, and elevated white blood cell count suggests diverticulitis.
Abdominal CT scan is the test of choice to diagnose diverticulosis and diverticulitis.
If diverticular bleeding is suspected, a colonoscopy is the test of choice to confirm the diagnosis and identify the site of bleeding.
Colonoscopy with biopsy to rule out colon cancer should be performed after the initial event has subsided.

Treatment

Nutrition is the primary consideration for prevention and treatment. The risk of developing diverticula can be reduced by increasing fiber intake, either through high-fiber foods or fiber supplements, along with other diet changes (see Nutritional Considerations).
Diverticulosis itself does not require treatment.
Diverticulitis generally requires hospitalization, intravenous fluids, and antibiotics.

Patients with diverticulitis have a 40 percent risk of recurrence after the initial episode and an 80 percent risk of recurrence following a second episode. To prevent recurrence, many patients will require surgical removal of the involved section of the colon.
Diverticular bleeding, if severe or recurrent, may require hospitalization, intravenous fluids, blood transfusions, and surgical removal of the involved area of colon.

Diverticular Disease: Nutritional Considerations

Researchers have been studying nutritional steps that can help prevent or treat diverticular disease. The following steps are under study:

High dietary fiber intake: Fiber-poor diets appear to be the primary cause of diverticular disease. Individuals who eat generous amounts of insoluble fiber have 40 percent lower risk of diverticular disease, compared to those consuming little dietary fiber. Good sources of insoluble fiber include wheat bran, legumes, skin of fruit, nuts, and seeds.
A meat-free diet: Not surprisingly, meat-eaters have a much higher incidence of diverticular disease (33 percent) compared with vegetarians (12 percent). Eating a diet low in fiber and high in meat increases the risk for symptomatic diverticular disease more than threefold. Furthermore, in patients who eat the largest amount of meat, the risk for diverticulosis of the right side of the colon may be as high as 25 times greater than patients who eat the least.
An active lifestyle: High levels of physical activity may have a protective effect against diverticular disease. Constipation, which is a known risk factor for diverticulitis, is related to inactivity. While moderate physical activity has little protective effect, more intense activity, such as jogging or running, appears to reduce risk by about 40 percent.