Diverticular Disease of the Colon

Diverticula are sac-like protrusions of the mucosa and submucosa that bulge through weak spots in the muscularis propria. They form when intraluminal pressure rises due to straining, chronic constipation, or low-fiber diets, forcing the mucosal layer outward through structurally vulnerable points where blood vessels penetrate the circular muscle layer.

The sigmoid colon has a relatively small diameter, which according to the Law of Laplace creates greater intraluminal pressure and increased tension on the colonic wall. This anatomical vulnerability, combined with segmental contractions that further raise pressure, makes the sigmoid colon the most common site for diverticula formation.

Diverticulosis is the presence of sac-like pouches in the colon, often asymptomatic and incidentally detected. Diverticulitis occurs when these pouches become inflamed or infected, typically presenting with left lower abdominal pain, fever, nausea, vomiting, and tenderness when stool becomes trapped and bacterial overgrowth develops.

Over time, the circular muscle layer thickens and the taeniae coli shorten, accompanied by increased collagen and elastin deposition. These changes stiffen the colon, impair motility, increase segmentation, and raise local pressure further, creating a cycle that promotes formation of additional diverticula.

Diverticulitis complications include micro- or macroperforation causing abscesses or peritonitis, and fistulas creating abnormal connections between the colon and bladder, leading to pneumaturia. Fibrosis may cause bowel obstruction, and vessel erosion can result in bleeding. These complications resemble clinical manifestations and complications seen in other gastrointestinal inflammatory conditions.

Diverticula form at weak points where blood vessels, specifically the vasa recta, penetrate the circular muscle layer to supply the mucosa. These entry points are structurally vulnerable and prone to herniation when intraluminal pressure builds up, allowing only the mucosa and submucosa to bulge through the muscular layer.

A low-fiber diet decreases stool bulk, reducing the volume that stimulates normal colonic contractions. This leads to increased straining during bowel movements and chronic constipation, both of which raise intraluminal pressure and force the mucosa outward through weak points in the bowel wall.