Incidence and Epidemiology
Among Western populations, diverticulosis of the colon affects nearly one-half of individuals older than age 60 years. Fortunately, only 20% of patients with diverticulosis develop symptomatic disease. However, in the United States, diverticular disease results in >200,000 hospitalizations annually, making it the fifth most costly gastrointestinal disorder. The incidence of the disease is on the rise, mainly among young patients. The mean age at presentation of the disease is 59 years. Although the prevalence among females and males is similar, males tend to present at a younger age. Diverticulosis is rare in underdeveloped countries, where diets include more fiber and roughage. However, shortly following migration to the United States, immigrants will develop diverticular disease at the same rate as U.S. natives.
Anatomy and Pathophysiology
Two types of diverticula occur in the intestine: true and false (or pseudodiverticula). A true diverticulum is a saclike herniation of the entire bowel wall, whereas a pseudodiverticulum involves only a protrusion of the mucosa through the muscularis propria of the colon (Fig. 297-1). The type of diverticulum affecting the colon is the pseudodiverticulum. The protrusion occurs at the point where the nutrient artery, or vasa recti, penetrates through the muscularis propria, resulting in a break in the integrity of the colonic wall. Diverticula commonly affect the sigmoid colon; only 5% of persons exhibit pancolonic diverticula. This anatomic restriction may be a result of the relative high-pressure zone within the muscular sigmoid colon. Thus, higher-amplitude contractions combined with constipated, high-fat-content stool within the sigmoid lumen results in the creation of these diverticula. Diverticulitis is inflammation of a diverticulum. The cause is not well understood and is probably multifactorial. The predominant theory is the retention of particulate material within the diverticular sac and the formation of a fecalith. Consequently, the vasa recti is either compressed or eroded, leading to either perforation or bleeding.
Gross and microscopic view of sigmoid diverticular disease. Arrows mark an inflamed diverticulum with the diverticular wall made up only of mucosa.
Presentation, Evaluation, and Management of Diverticular Bleeding
Hemorrhage from a colonic diverticulum is the most common cause of hematochezia in patients >60 years, yet only 20% of patients with diverticulosis will have gastrointestinal bleeding. Patients at increased risk for bleeding tend to be hypertensive, have atherosclerosis, and regularly use nonsteroidal anti-inflammatory agents. Most bleeds are self-limited and stop spontaneously with bowel rest. The lifetime risk of rebleeding is 25%.
Localization of diverticular bleeding should include colonoscopy, which may be both diagnostic and therapeutic in the management of mild to moderate diverticular bleeding. If the patient is stable, massive bleeding is best managed by angiography. Mesenteric angiography can localize the bleeding site and occlude the bleeding vessel successfully with a coil in 80% of cases. The patient can then be followed closely with repetitive colonoscopy, if necessary, looking for evidence of colonic ischemia. Alternatively, a segmental resection of the colon can be undertaken to eliminate the risk of further bleeding. This may be advantageous in patients on chronic blood thinners. However, with newer techniques of highly selective coil embolization, the rate of colonic ischemia is <10% and the risk of acute rebleeding is <25%. Long-term results (40 months) indicate that more than 50% of patients with acute diverticular bleeds have had definitive treatment with highly selective angiography.
As another alternative, a selective infusion of vasopressin can be given to stop the hemorrhage, although this has been associated with significant complications, including myocardial infarction and intestinal ischemia. Furthermore, bleeding recurs in 50% of patients once the infusion is stopped. Localization studies indicate that bleeding as a result of colonic diverticulosis is more often seen from the right colon. For this reason, patients with presumed bleeding from diverticular disease requiring emergent surgery without localization should undergo a total abdominal colectomy. If the patient is unstable or has had a 6-unit bleed within 24 h, current recommendations are that surgery should be performed. In patients without severe comorbidities, surgical resection can be performed with a primary anastomosis. A higher anastomotic leak rate has been reported in patients who received >10 units of blood.
Presentation, Evaluation, and Staging of Diverticulitis
Acute uncomplicated diverticulitis characteristically presents with fever, anorexia, left lower quadrant abdominal pain, and obstipation (Table 297-1). In <25% of cases, patients may present with generalized peritonitis indicating the presence of a diverticular perforation. If a pericolonic abscess has formed, the patient may have abdominal distention and signs of localized peritonitis. Laboratory investigations will demonstrate a leukocytosis. Rarely, a patient may present with an air-fluid level in the left lower quadrant on plain abdominal film. This is a giant diverticulum of the sigmoid colon and is managed with resection to avoid impending perforation.
Table 297-1 Presentation of Diverticular Disease
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Table 297-1 Presentation of Diverticular Disease
|Uncomplicated Diverticular Disease—75%|
|Complicated Diverticular Disease—25%|
The diagnosis of diverticulitis is best made on CT with the following findings: sigmoid diverticula, thickened colonic wall >4 mm, and inflammation within the pericolic fat ± the collection of contrast material or fluid. In 16% of patients, an abdominal abscess may be present. Symptoms of irritable bowel syndrome (IBS) may mimic those of diverticulitis. Therefore, suspected diverticulitis that does not meet CT criteria or is not associated with a leukocytosis or fever is not diverticular disease. Other conditions that can mimic diverticular disease include an ovarian cyst, endometriosis, acute appendicitis, and pelvic inflammatory disease.
Barium enema or colonoscopy should not be performed in the acute setting because of the higher risk of colonic perforation associated with insufflation or insertion of barium-based contrast material under pressure. A sigmoid malignancy can masquerade as diverticular disease. Therefore, a colonoscopy should be performed ˜6 weeks after an attack of diverticular disease.
Complicated diverticular disease...