Incidence and Epidemiology
In the United States, diverticulosis affects 60% of the population aged >60 and up to 30% of individuals with diverticular disease will experience recurrent symptoms. Diverticular disease has become the fifth most costly gastrointestinal disorder in the United States and is the leading indication for elective colon resection. The incidence of diverticular disease is on the rise. Fortunately, only 20% of patients with diverticulosis develop diverticular disease and 4% require hospitalization. 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 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. 321-1). The type of diverticulum most commonly affecting the colon is the pseudo diverticulum. 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. Yamanda et al. found right-side colonic diverticulosis in 22% of Japanese patients undergoing colonoscopy. 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 in neuronal degeneration leading to dysmotility and high intraluminal pressure. As a consequence, pockets or outpouchings develop in the colonic wall where it is weakest. Furthermore, better understanding of the gut microbiota suggests that dysbiosis is an important aspect of disease.
Gross and microscopic view ...