Although uncommon in developing countries, diverticular disease is increasingly prevalent in industrialized nations. Radiographic and autopsy data indicate that the prevalence of diverticulosis increases with age: 5% in patients age <40 years, 30% by age 60, and >70% by age 85.^1,2 One study noted a 26% jump in hospital admissions between 1998 and 2005, particularly in patients less than 45 years of age.³

In most patients, diverticular disease is an incidental finding. The natural history of the disease appears to be quite benign. One study followed 2366 Kaiser Permanente patients hospitalized with acute diverticulitis and treated nonoperatively. Of those, 86% required no further inpatient care for diverticulitis during a 9-year follow-up period. Only 4% had a second recurrence. No patient with a second recurrence required an operation.⁴

Diverticula are small herniations at sites where the vasculature, called vasa recta, penetrates the circular muscle layer of the colon. Although true diverticula involve all layers of the colon wall, most acquired diverticula are considered false diverticula, involving only the mucosal and submucosal layers. Diverticula usually range from 5 to 10 mm, but can extend up to 20 mm in length. Diverticulitis occurs when inflammation develops and in complicated diverticulitis, leading to translocation of bacteria, microperforation, and abscess or phlegmon formation.⁵

There are similar chemical and histologic changes seen in inflammatory bowel disease and irriTable bowel syndrome, but no unifying mechanism has been demonstrated.^5,6 The most common bacterial pathogens isolated are anaerobes, including Bacteroides, Peptostreptococcus, Clostridium, and Fusobacterium as well as gram-negative rods, such as Escherichia coli.

Altered bowel motility leads to high intraluminal colonic pressures and diverticula formation. The role of diet remains unclear. Smoking and obesity increase risk for diverticulitis, and an active lifestyle is said to decrease the risk. Nonsteroidal anti-inflammatory drugs, opioids, and steroids increase the risk of perforation.⁵

In the United States, diverticular disease is almost exclusively a left-sided colon disease, specifically the descending and sigmoid colon. Right-sided disease accounts for only 2% to 5% of cases and is found predominantly in Asian populations.⁷

Classically, diverticulitis presents with left lower quadrant abdominal pain, fever, and leukocytosis. Patients with a redundant sigmoid colon, of Asian descent, or with right-sided disease may complain of right lower quadrant or suprapubic pain. The pain may be intermittent or constant and often associated with a change of bowel habits, either diarrhea or constipation. Other associated symptoms include nausea/vomiting, anorexia, and urinary symptoms. On physical examination, patients may exhibit findings ranging from mild abdominal tenderness to moderate tenderness with a tender palpable mass to peritonitis with rebound and guarding.

In sTable patients with a history of confirmed diverticulitis and a similar acute presentation, no further diagnostic evaluation is necessary unless the patient fails to improve with conservative medical treatment. If a prior diagnosis has not been confirmed or the current episode differs from the past episode, diagnostic imaging is required to exclude other intra-abdominal pathology and to evaluate for complications. The differential diagnosis of diverticulitis is extensive, including gynecologic emergencies, cancer, and inflammatory or infectious colitis (Table 82-1). Laboratory data are rarely diagnostic for diverticulitis, but liver function panels, CBC, renal panel, lipase, and urinalysis may aid in the exclusion of other disorders.

IMAGING

CT is the preferred imaging modality because of its ability to evaluate the severity of disease and the presence of complications. CT with IV and oral contrast has documented sensitivities of 97% and specificities approaching 100%.⁸ CT findings include increased soft tissue density within the pericolic fat, indicating inflammation; presence of diverticula; bowel wall thickening >4 mm; soft tissue masses, representing phlegmon; or pericolic fluid collections, representing abscesses.⁸