Pathophysiology

Colonic diverticula are defects of the large colon, especially the sigmoid, that develop with advancing age. They are saclike herniations of the mucosa through the muscularis propria and are actually pseudodiverticular because they do not contain the muscle layer.

The pathophysiologic changes common to all cases of diverticulosis of the colon are not entirely clear. Herniation of the muscle layer of the colon is the result of two factors: (1) an increased pressure gradient between the colonic lumen and the serosa and (2) areas of relative weakness in the colonic wall.¹

One commonly accepted hypothesis of diverticula formation is that low-fiber diets decrease the amount of intraluminal bulk in the colon, causing muscle hypertrophy as the colon tries to move the fecal matter along.¹ Lack of fecal bulk is thought to produce uncoordinated and irregular colonic peristalsis, which creates sacculations in the colon wall. There is increased pressure within these sacs, which results in diverticular outpouchings. These sacs occur at weak points, or natural breaks, in the muscle layer of the colon where the nutrient vessels, the vasa recta, pass through the muscularis propria into the submucosa. In addition, the colon wall, which is covered by connective tissue, loses its flexibility and tensile strength with age. A weakened bowel wall develops and may predispose an individual to formation of diverticula.

Increasing dietary fiber intake will reduce the incidence of diverticular disease; accordingly, vegetarians have a reduced risk for diverticular disease.¹ Additional risk factors for diverticular disease include consumption of red or processed meats, obesity, and smoking.³

In terms of size and distribution, diverticula range from 1 or 2 mm to giant diverticula. In Western societies, diverticula occur predominantly in the sigmoid colon. In Asians, right-sided diverticula are more common.⁴

Clinical Presentation

Patients with uncomplicated colonic diverticula, or diverticulosis, are often asymptomatic and rarely seek medical attention; approximately 75% of these individuals are never seen with a clinical problem.^1,6 Of the 25% of patients with acute diverticulitis who are seen, 15% will develop significant complications including fistulas, abscesses, and perforations.³ Symptomless diverticula are often noted when the colon is studied for another reason with a barium enema, colonoscopy, computed tomography (CT) scan, or ultrasound examination.

Symptomatic patients may complain of irregular defecation, intermittent abdominal pain, bloating, or excessive flatulence. In general, there is a change in stool caliber, with descriptors that can range from flattened or ribbon-like to hard pellets. Associated complaints include urinary dysfunction, anorexia, nausea, vomiting, and heartburn. Older individuals often relate recurrent bouts of steady or crampy pain (mostly in the left lower quadrant) in combination with constipation or alternating periods of diarrhea and constipation. They may also have abdominal distention that is relieved by the passage of flatus or stool. These symptoms can often mimic irritable bowel syndrome except that they are experienced at an older age. Patients with right-sided pain tend to be younger, and their pain is easily mistaken for appendicitis. Immunocompromised patients may be asymptomatic longer because of ineffective inflammatory response, making them at higher risk for complications.¹

Physical Examination

For patients with uncomplicated symptoms, the findings of the physical examination (including both pelvic and rectal examinations) are usually normal. Fever is possible but may not be present. The other vital signs are often normal except in the presence of a massive diverticular bleed; tachycardia and hypotension are not uncommon. Most often, physical findings reveal mild, left lower quadrant tenderness with a thickened palpable sigmoid and descending colon. Isolated right lower quadrant tenderness also may be related to diverticulitis. Tenderness throughout the abdomen suggests perforation and peritonitis.⁷ Rectal bleeding is infrequent, but painless bright red bleeding or maroon-colored stools suggest a diverticular bleed.⁷

Diagnostics

A complete blood count (CBC) and urinalysis should be obtained. Screening laboratory values should be normal in uncomplicated diverticulosis; leukocytosis may be present in diverticulitis. A stool specimen for occult blood is necessary because uncomplicated diverticulosis is not known to cause occult rectal bleeding. Plain abdominal x-ray films will be normal and are unnecessary, although they are sometimes ordered to exclude the presence of free air in the abdomen. Rigid sigmoidoscopy usually cannot be performed beyond the rectosigmoid junction and for this reason is not particularly useful. The diagnosis of diverticulosis is most often established with a barium enema examination; this method is the best for determination of the extent and severity of the disease. Barium enemas should be avoided in acute diverticulitis because of the risk of extravasation of barium into the peritoneal cavity, causing chemical peritonitis. Chemical peritonitis increases the risk of mortality. A substitution for barium enema would be a water-soluble enema. Although it is often used as a diagnostic tool, colonoscopy is best used to assess the large bowel for a coexisting pathologic condition rather than for an actual diagnosis of diverticular disease.¹

A CT scan of the abdomen and pelvis with contrast enhancement is the preferred imaging study if acute diverticulitis is suspected. However, CT scan is not indicated for all patients but should be considered if peritonitis, a diverticular abscess, or other complication is suspected. Unless pregnancy is ruled out, the recommended imaging modality for women of childbearing age with acute abdominal pain is sonography.^8,9

Differential Diagnosis

The hallmark of symptomatic diverticulosis is colicky abdominal pain in the absence of an inflammatory process. The cause of this pain is not fully understood but possibly is related to spasms in the sigmoid colon or an element of obstruction related to the spasms. This clinical entity must be differentiated from diverticulitis and any disease that causes abnormal intestinal motility.

The challenge is not so much in making the diagnosis as it is in distinguishing patients who have symptomatic diverticular disease from those who have diverticula plus other lesions that may be responsible for the symptoms. Irritable bowel syndrome and colorectal cancer should be considered in the differential diagnosis. In patients with localized right-sided abdominal pain, appendicitis must be considered.¹

Fiber is essential to reduce the risk of constipation. In the United States, adults consume approximately 11 to 23 g of fiber per day, half of the 27 to 40 g of daily fiber recommended by the World Health Organization and less than the 20 to 35 g proposed by the American Dietetic Association.² Increased fiber intake can be achieved through the consumption of whole grains and cereals, fruits, vegetables, and legumes. These foods should be introduced gradually during a period of weeks to months to avoid excessive bloating and flatulence. Bran, a concentrated form of fiber, can be used as an adjunct to fiber consumption but should not be a replacement for other high-fiber foods. Some patients may need 2 g of bran three times a day to provide the bulk; it should be soaked or mixed in media such as hot cereal, applesauce, juice, or milk.² Fiber can also be given through commercially available high-fiber supplements or bulk formers such as psyllium hydrophilic mucilloid, methylcellulose, and calcium polycarbophil. These products work similarly to bran and must be taken with several glasses of fluid to be effective. They produce a softer, more frequent stool.¹⁰

Current literature does not support the elimination of certain dietary foodstuffs in the management of diverticulosis. Diets high in dietary fiber and low in saturated fat, along with the avoidance of red meat, have minimal evidence in reducing the risk of diverticulosis. They do have promising support in clinical trials to lower the risks of colon cancer.^11,12

Anticholinergic and antispasmodic agents have been used without substantiated evidence of their effectiveness. They may be used to relieve spasms. Care should be taken to avoid constipation.

Surgical resection for pain relief, in the absence of documented inflammatory complications, is associated with a high rate of symptom recurrence and is therefore not recommended.¹

Life Span Considerations

Diverticular disease is usually observed in adults older than 40 years, and incidence increases with age. Younger adults, however, can develop diverticular disease and associated complications such as diverticulitis and diverticular bleeding.¹

Complications

The most common complication of diverticular disease is acute diverticulitis. Hemorrhage from diverticula is also a common complication, occurring in 5% to 15% of patients; 3% to 5% of cases are severe. Hemorrhage is more common from the right colon. Other complications that are less common include abscess, bowel perforation, peritonitis, strictures, fistulas, and small bowel obstructions.³

Indications for Referral or Hospitalization

Uncomplicated diverticular disease can be managed in the primary care setting. Questionable radiographic findings on any barium studies necessitate referral to a gastroenterologist for further evaluation. Patients with suspected diverticular abscess or rectal bleeding need further evaluation, and a referral or consultation is indicated for lower endoscopy.

Although the health care provider assumes responsibility for patient education, a referral to a dietitian may be beneficial for patients with recurrent, painful disease.

Patient and Family Education and Health Promotion

The patient’s diet and symptoms should be reviewed at every session for prevention and health promotion. All patients need to be instructed about a nutritionally well-balanced diet that includes whole-grain breads and cereals and fresh fruits and vegetables to attain the benefits of both types of fiber. The goal of 30 to 35 g of fiber per day requires the consumption of five fruits and vegetables (15 g), four high-fiber starches (8 g), and one high-fiber cereal (7 g).

It is important that patients be advised to increase their fiber intake gradually to prevent flatulence and abdominal discomfort. Patients can often tolerate 5- to 10-g increments every few weeks on the basis of symptoms. Bloating or flatulence resulting from bran intake usually resolves with continued use. If patients are taking pharmaceutical fiber supplements, it is especially important that they increase their fluid intake to at least eight 8-ounce glasses of fluid per day. Maintenance of ideal body weight, daily exercise, reduced consumption of red and processed meats, and avoidance of tobacco and alcohol and the routine use of nonsteroidal anti-inflammatory drugs also reduce the risks of development of diverticula.^13–15