Diverticula of the large bowel are outpouchings of the mucosa and submucosal layers of the bowel wall which protrude via deficits in the muscularis layers. The accumulation of multiple diverticula gives rise to diverticular disease, or diverticulosis. When these pouches become inflamed or infected, it gives rise to diverticulitis.
Among diverticulosis patients, approximately 10-25% develop diverticulitis, or inflammation of the diverticula. An additional 5-15% of patients develop diverticular bleeding, which results when an adjacent blood vessel ruptures into a diverticulum. In adults, diverticular bleeding is the most common cause of brisk rectal bleeding. While the majority of diverticula in the Western world occurs in the sigmoid colon, the majority of diverticular bleeds occur in the right side of the colon, possibly due to thinner mucosal wall and wider domed diverticula in that colonic portion.
The prevalence of diverticulosis has increased both in the Western hemisphere and in countries that have adopted a more Western lifestyle. The prevalence is 5-45% in Western countries and 3-25% in Asia. While the sigmoid and distal colon is involved in 70-98% of patients in Western countries, the right side of the colon is the main site of involvement in Asia. Diverticular disease has been traditionally viewed as a disease affecting elderly patients, but acute admissions of middle-aged and younger patients have become more common.
Diverticulosis is usually asymptomatic, although patients may give a history of mild lower abdominal pain, cramping, bloating, constipation, and/or diarrhea. Diverticulitis presents with fever, severe lower abdominal pain and tenderness, nausea, and vomiting. Diverticular bleeding may present as guaiac-positive stools, iron-deficiency anemia, or frank hematochezia. Potentially life-threatening complicated disease such as abscess, perforation, or major hemorrhage can occur.
As described below, high-fiber diets have been associated with decreased rates of symptomatic diverticular disease, while diets high in meat and fat are associated with increased incidence. It is hypothesized that a lack of fiber renders the stool dry and low in bulk, which increases transit time and the segmental pressure required to propel the stool through the colon. Over time, this increased pressure is thought to result in the formation or progression of diverticula. In contrast, high fiber intake results in stool that is of adequate bulk and consistency, which allows for easy passage.
Advancing age. Diverticula are present in nearly half of Americans by age 60, and more than 2/3 of Americans over age 80 are affected. In contrast, less than 5% of people under age 40 are affected. However, between 1998 and 2005, there was an observed 82% increase in admission rates for diverticulitis in patients ages 18-44.
Affluence. Industrialized countries have a much higher prevalence of diverticular disease than developing nations. Some Western nations have prevalence rates that approach 40%, whereas developing countries in Asia and Africa have prevalence well below 1%. Adoption of a Western lifestyle is associated with increased rates of diverticulosis in countries with previously low prevalence.
Inadequate dietary fiber intake. Large prospective studies have linked a low fiber intake to the development of symptomatic and complicated diverticular disease (see Nutritional Considerations below)., Those who consume a vegetarian diet with high fiber intake (≥ 40 g/day) appear to have a decreased prevalence of diverticulosis. It is not clear, however, that fiber reduces the occurrence of asymptomatic diverticular disease.,
The “fibre hypothesis”—that a fiber-deficient diet contributes to unfavorable changes in stool bulk and content, bacterial flora, total transit time, and intraluminal pressures, leading to diverticulosis and other disease—has subsequently been validated by dozens of groups and remains incredibly relevant in the 21st century. Consumption of insoluble fiber (legumes, fruit skins, whole wheat, etc) may be particularly protective, reducing the risk of symptomatic diverticular disease by 40%.
Red meat intake. Red meat consumption has been correlated with a higher risk for diverticular disease, independent of fiber intake., The Health Professional Follow-Up Study demonstrated that as little as 1 serving of meat per week is associated with increased risk, with men in the highest quintile for meat consumption at 58% increased risk of acute diverticulitis.
Sedentary lifestyle. Regular physical activity of at least moderate intensity, such as running, reduces risk for diverticulitis or diverticular bleeding by about 40%., Constipation is a possible risk factor for diverticulitis and is related to inactivity.
Obesity. In a large prospective cohort study, among men ages 40-75, elevated body mass index, waist-to-hip ratio, and waist circumference were all significantly associated with diverticulitis or a diverticular bleed.
Asymptomatic diverticulosis is often incidentally identified on colonoscopy, abdominal CT scan, or barium enema.
If diverticular bleeding is suspected, a colonoscopy may identify the site of bleeding and confirm the presence of diverticula. Upper gastrointestinal endoscopy should also be considered to rule out upper gastrointestinal bleeding. If the source of bleeding cannot be identified, then a tagged red blood cell scan plus angiography may help isolate the problematic vessel. Diverticular bleeding usually occurs in the absence of diverticulitis.
The triad of left lower abdominal pain, fever, and leukocytosis suggests diverticulitis. Asian patients may have right-sided lower abdominal pain. Abdominal CT scan is the diagnostic test of choice.
Colonoscopy and barium enema may increase the risk of colonic perforation and are contraindicated in acute diverticulitis. However, after the acute phase has subsided (at least 6 weeks out), colonoscopy with biopsy of any suspicious areas should be performed. Follow-up colonoscopy may not be necessary in select patients who have had recent colon cancer screening via colonoscopy.
Nutrition is the primary consideration for prevention and treatment of diverticulosis. Increasing fiber intake, either through high-fiber foods or psyllium-based fiber supplements, along with other diet changes, may reduce the risk of developing diverticula (see Nutritional Considerations below).
Uncomplicated diverticulitis is treated with bowel rest (no oral intake of food, drink, or medications) and antibiotics.
Patients with acute left-sided diverticula have a 20-40% risk of recurrent bouts. According to the Practice Parameters of the American Society of Colon and Rectal Surgeons (2014), increasing evidence supports waiting for more than 2 episodes before surgical intervention, as there is no increase in complications or colostomy rate after 4 episodes compared with 1 (of sigmoid diverticulitis). However, surgery may be considered for even a single episode of diverticulitis in patients who are immunocompromised, are ≤ 40 years of age, or have right-sided diverticula.
Right-sided diverticulitis and subsequent recurrences are much less common than left-sided disease in Western populations, and medical management and intervention options are based on individual presentation. Options can range from routine medical therapy to diverticulectomy to right hemicolectomy, based on degree of inflammation and patient health status.
Diverticulitis that is complicated by fistula formation, colonic perforation, or bowel obstruction or that fails to respond to medical therapy is treated emergently with individualized surgical intervention.
Most cases of diverticular bleeding resolve spontaneously. However, in severe or recurrent cases, patients may require immediate fluid resuscitation and blood transfusion, along with endoscopic, angiographic, or surgical intervention of the involved area of the colon.
Diverticular disease is associated with a fiber-poor diet, i.e., a diet low in fruits, vegetables, whole grains, and legumes but high in animal products and/or refined foods.
Some practitioners have suggested avoiding nuts, seeds, popcorn, corn, and other high-residue foods on the theory that they may lodge within a diverticulum or abrade the mucosa and cause inflammation or bleeding. This idea has had little objective support. In the Health Professionals Follow-Up Study including 47,228 men aged 40-75 years, nut and popcorn consumption was inversely associated with the risk of diverticulitis. That is, nut and popcorn consumption is associated with reduced risk.
The following factors have been associated with a reduced risk of diverticular disease in epidemiologic studies:
A high-fiber diet. Fiber-poor diets may play a role in diverticular formation. Fiber may protect against colonic perforation by increasing stool bulk and water content, resulting in a decreased fecal transit time and reduction of colonic segmentation pressures. Moreover, fiber beneficially alters the gut microbiome and reduces inflammation.
Individuals eating generous amounts of insoluble fiber (e.g., wheat bran, legumes, fruit skin, nuts, seeds) have roughly a 40% lower risk of symptomatic diverticular disease, compared with those consuming little dietary fiber. Data from the Million Women Study support the high-fiber hypothesis and found that fiber from fruits and grains is especially protective.
Determining the exact role of fiber in diverticulosis development and treatment requires more research, but recommending a high-fiber diet remains prudent.
A vegan diet. The prevalence of diverticular disease in British vegetarians in the late 1970s was reported to be approximately one-third that of meat eaters. The more recent European Prospective Investigation into Cancer and Nutrition (EPIC) prospective study showed that vegans have a 72% reduced risk of diverticular disease, compared with meat eaters. High dietary fiber intake was again shown to be an independent factor, reducing the relative risk of diverticular disease by 41%.
Avoiding meat. Fiber intake and meat intake are not entirely independent variables; like all animal products, meat contains no fiber. However, meat consumption has stood out as a risk factor for diverticular disease. Eating a diet low in fiber and high in meat is associated with a 3-fold increased risk for symptomatic diverticular disease.
In persons eating the largest amount of meat, the risk for right-sided diverticulosis in particular is roughly 25 times that of persons eating the least. Men in the Health Professionals Follow-Up Study in the highest quintile of meat consumption were 58% more likely to develop diverticulitis. As little as 1 serving of meat per week increased risk in this cohort. Unprocessed meat, such as steak, had the highest risk, possibly due to higher cooking temperatures or from larger pieces reaching the large intestine undigested.
In contrast, people following vegetarian diets typically consume more fiber, but their lower risk of diverticular disease is partly independent of fiber intake, suggesting the possibility of other mechanisms by which plant-based foods reduce risk.
Attainment or maintenance of a healthy weight. Prospective cohort studies have found a linear increase in risk for diverticulitis for body mass indexes greater than 25., A cross-sectional study with 126 white males found those with a waist circumference greater than 45 in were 8.1 times more likely to have diverticulosis than those with a waist circumference less than 38 in.
During symptomatic episodes, avoiding solid foods and staying hydrated on a liquid diet or intravenous fluids in combination with antibiotics is helpful.
See Basic Diet Orders chapter.
What to Tell the Family
Diverticula are outpouchings of the lining of the gut caused by multiple factors, but these can progress to a clinical disease state if chronically increased colonic pressure is present. Symptomatic disease seems to be a result of a low-fiber diet. Family members can help by serving plenty of high-fiber vegetables, fruits, beans, and whole grains at home and eating these foods themselves. Diet changes are much more likely to be permanent when the whole family joins in.
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