Incidence and Epidemiology
In the United States, diverticulosis affects 70% of the population above the age of 80. Fortunately, only 20% of patients with diverticulosis develop symptomatic disease, 1–2% require hospitalization, and <1% will require surgery. Diverticular disease has become the fifth most costly gastrointestinal disorder in the United States. Previously overlooked, the majority of patients with diverticular disease report a lower health-related quality of life and more depression as compared to matched controls, thus adding to health care costs. Formerly, diverticular disease was confined to developed countries; however, with the adoption of westernized diets in underdeveloped countries, diverticulosis is on the rise across the globe. Immigrants to the United States develop diverticular disease at the same rate as U.S. natives. Although the prevalence among females and males is similar, males tend to present at a younger age. The mean age at presentation of the disease is 59 years and is now shifting to affect younger populations.
Anatomy and Pathophysiology
Two types of diverticula occur in the intestine: true and false (or pseudo diverticula). A true diverticulum is a saclike herniation of the entire bowel wall, whereas a pseudo diverticulum involves only a protrusion of the mucosa and submucosa through the muscularis propria of the colon (Fig. 353-1). The type of diverticulum affecting the colon is the pseudodiverticulum. Diverticula commonly affect the left and sigmoid colon; the rectum is always spared. However, in Asian populations, 70% of diverticula are seen in the right colon and cecum as well. Diverticulitis is inflammation of a diverticulum. Previous understanding of the pathogenesis of diverticulosis attributed a low-fiber diet as the sole culprit, and onset of diverticulitis would occur acutely when these diverticula become obstructed. However, evidence now suggests that the pathogenesis is more complex and multifactorial. The diverticula occur 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. 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 in an area of weakness in the colonic wall results in the creation of these diverticula. Consequently, the vasa recti is either compressed or eroded, leading to either perforation or bleeding. Chronic low-grade inflammation is thought to play a key role. Furthermore, better understanding of the gut microbiota suggests that dysbiosis is an important aspect of disease.
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