Clinical meaning
Diverticular disease encompasses two related conditions: diverticulosis (the presence of diverticula) and diverticulitis (inflammation or infection of diverticula). Diverticula are small pouch-like herniations of the colonic mucosa and submucosa through weakened areas of the muscular layer, typically at points where blood vessels (vasa recta) penetrate the circular muscle. This creates false diverticula containing only mucosa and submucosa, unlike true diverticula that contain all bowel wall layers. The pathogenesis of diverticulosis involves two key factors: structural weakness in the colonic wall and increased intraluminal pressure. Low dietary fibre leads to reduced stool bulk, which requires the colon to generate higher segmental pressures to propel smaller stool volumes. These elevated pressures act on structurally weakened points in the colonic wall (where vasa recta penetrate), causing mucosal herniation. Age-related changes in collagen composition and elasticity further weaken the bowel wall, explaining why diverticulosis prevalence increases from less than 10% at age 40 to over 60% by age 80. Diverticulosis is predominantly left-sided (95% involve the sigmoid colon) in Western populations due to the sigmoid colon's smaller diameter (Laplace law: pressure is inversely related...