A diverticulum is a blind pouch leading off the alimentary tract, lined by mucosa that communicates with the gut lumen. Congenital diverticula contain all 3 layers of the bowel wall; the prototype is the Meckel's diverticulum which occurs in the ileum. Virtually all other diverticula are acquired and either lack or have an attenuated muscularis propria. Diverticula occur anywhere in the gastrointestinal tract but are most common in the colon, especially the sigmoid colon, where over the age of 60, the prevalence approaches 50%.
The pathogenesis is related to increased luminal pressure and focal weakness in the colonic wall. Increased luminal pressure occurs secondary to exaggerated peristaltic movements which in turn is related to decreased stool bulk secondary to decreased dietary fibre. Focal wall weaknesses occur at points where nerves and blood vessels penetrate the inner circular muscle coat alongside the taeniae coli. Most patients are asymptomatic but some manifest with abdominal pain. Inflammatory and obstructive complications can ensue and require surgery.