Colonic diverticulosis increases with age, ranging from a prevalence of 5% in those under age 40 to over 50% by age 60 years in Western societies. Most are asymptomatic, discovered incidentally at endoscopy or on barium enema. Complications occur in less than 5%, including gastrointestinal bleeding and diverticulitis.
Colonic diverticula (eFigure 15–30) may vary in size from a few millimeters to several centimeters and in number from one to several dozen. Almost all patients with diverticulosis have involvement in the sigmoid and descending colon; however, only 15% have proximal colonic disease.
Three colonic diverticula. (Used, with permission, from R. McClean.)
For over 40 years, it has been believed that diverticulosis arises after many years of a diet deficient in fiber. It is hypothesized that undistended, contracted segments of colon have higher intraluminal pressures. Over time, the contracted colonic musculature, working against greater pressures to move small, hard stools, develops hypertrophy, thickening, rigidity, and fibrosis. Diverticula may develop more commonly in the sigmoid because intraluminal pressures are highest in this region. Recent epidemiologic studies challenge this theory, finding no association between the prevalence of asymptomatic diverticulosis and low dietary fiber intake or constipation. Thus, the etiology of diverticulosis is uncertain. The extent to which abnormal motility and hereditary factors contribute to diverticular disease is unknown. Patients with abnormal connective tissue are also disposed to development of diverticulosis, including Ehlers-Danlos syndrome, Marfan syndrome, and systemic sclerosis.
1. UNCOMPLICATED DIVERTICULOSIS
More than 90% of patients with diverticulosis have uncomplicated disease and no specific symptoms. In most, diverticulosis is an incidental finding detected during colonoscopic examination or barium enema examination. Some patients have nonspecific complaints of chronic constipation, abdominal pain, or fluctuating bowel habits. It is unclear whether these symptoms are due to alterations in the colonic motility, visceral hypersensitivity, gut microbiota, or low-grade inflammation. Physical examination is usually normal but may reveal mild left lower quadrant tenderness with a thickened, palpable sigmoid and descending colon. Screening laboratory studies should be normal in uncomplicated diverticulosis.
There is no reason to perform imaging studies for the purpose of diagnosing asymptomatic, uncomplicated disease. Diverticula are well seen on barium enema, colonoscopy, and CT imaging. Involved segments of colon may also be narrowed and deformed.
Patients in whom diverticulosis is discovered should be encouraged to increase dietary fiber either through diet (fruits, vegetables, whole grains) or fiber supplements (psyllium, methylcellulose), which is associated with a lower risk of diverticulitis in prospective cohort studies. Studies suggest that the risk of diverticulitis may be further reduced with exercise and avoidance of red meats and NSAIDs.
et al. Intake of dietary fiber, fruits, and vegetables and risk of diverticulitis. Am J Gastroenterol. 2019;114:1531.