Acquired diverticular disease affects approximately 5 to 10 percent of the Western population older than 45 years and approximately 80 percent of persons older than 85 years. Ferzoco and colleagues review the diagnosis and treatment of this gastrointestinal condition.

It is estimated that 20 percent of patients with diverticula will develop symptomatic diverticulitis requiring medical or surgical intervention. Up to 20 percent of these patients will be younger than 50 years. Diverticulitis is thought to be more severe in younger patients, but this may be a result of delayed diagnosis. Recent data have also shown that diverticulitis has a similar incidence in men and women and that up to two thirds of patients younger than 50 years of age will remain disease-free for up to nine years after the initial attack.

Colonic diverticula are related primarily to two factors: increased intraluminal pressure and a weakening of the bowel wall. Patients with known diverticula have been found to have elevated resting colonic pressures. The Western diet, which tends to be low in dietary fiber and high in refined carbohydrates, is also believed to be a contributing factor. Once the pockets of diverticula form between the mesenteric and lateral taeniae coli, particles of undigested food may become inspissated within them. This results in obstruction at the neck of the diverticulum, allowing for increased mucus secretion and overgrowth of normal colonic bacteria, which produces overdistention of the diverticular sacs and microperforations. What follows is clinical disease, which may range from small pericolonic abscesses to fecal peritonitis. Colovesical fistulae formation is the most common complication; colovaginal and colocutaneous fistulae are less common.

The clinical diagnosis of diverticulitis is suggested by abdominal pain that is initially hypogastric but then localizes to the left lower quadrant. Urinary symptoms may occur if the affected colonic segment is close to the bladder. A lower quadrant abdominal or rectal mass may be palpated, but associated rectal bleeding is uncommon and suggests an alternative diagnosis. About 85 percent of cases of acute diverticulitis involve the descending or sigmoid colon; however, right-sided disease may also occur and is reported more frequently in persons of Asian descent. Sigmoid diverticulitis may mimic acute appendicitis if a redundant colon is in the suprapubic region or lower right quadrant.

Previously, diverticular disease was diagnosed using a contrast barium enema. However, because of the possibility of an obstructing fecalith being dislodged by insufflation and causing bowel perforation, computed tomographic (CT) scanning is now the diagnostic procedure of choice. Besides being safe and cost-effective, CT can also be used to assist percutaneous drainage of an abscess. False-negative rates using CT are reported to range from 2 to 21 percent. Ultrasonography has been advocated for the diagnosis and treatment of acute diverticulitis but is more operator-dependent than CT. Abdominal tenderness may prevent adequate use of pressure and produce suboptimal images. Neither ultrasound nor CT can distinguish between an inflammatory and a neoplastic mass.

Treatment of diverticulitis can proceed on an outpatient basis for a patient with a mild first attack who is able to tolerate oral hydration and an antibiotic. Treatment consists of a liquid diet and seven to 10 days of therapy with broad-spectrum antimicrobials such as metronidazole and ciprofloxacin. Patients with more severe illness, or those who cannot tolerate oral hydration or who have pain severe enough to require narcotic analgesia, should be hospitalized. Because feeding increases intracolonic pressure, patients should receive nothing by mouth and should be treated with intravenous triple therapy consisting of ampicillin, gentamicin and metronidazole. Alternative monotherapy includes piperacillin or tazobactam. If narcotics are required for pain control, meperidine is recommended because morphine sulfate causes colonic spasm. If pain, fever and leukocytosis do not resolve within three days, further imaging studies are indicated. If an abscess is uncovered and is more than 5 cm in size, CT-guided drainage and adequate antibiotic coverage should be considered.

Approximately 20 percent of patients with diverticulitis will require surgical intervention. Bowel resection is usually recommended for recurrent episodes of diverticulitis or if fistulae are present. Resection with primary anastomosis is now the procedure of choice unless generalized peritonitis has occurred, in which case a two-stage procedure is usually necessary. Rarely is the older three-stage Hartmann's procedure required. Twenty-seven percent of patients will still have some recurrence of symptoms even after surgery.

The authors believe it is prudent for all patients with diverticulitis, even those who have undergone surgical resection, to be encouraged to maintain a diet high in fiber. In addition, the authors recommend that all patients who recover without surgical intervention undergo colonoscopy to rule out the presence of a neoplasm.