Colonic diverticula are herniations of mucosa through the bowel musculature. They are seen most often in the sigmoid and descending colon, with a prevalence of up to 65% over the age of 80 in European populations, but they are uncommon in African and Asian countries, where the prevalence is 0.2%. A lifelong diet deficient in dietary fibre is associated with their development, but it is not known why some diverticula become symptomatic. A rise in intradiverticular pressure may play a role in perforation. Diverticula are usually discovered incidentally, but symptoms which are attributable to diverticular disease include colicky abdominal pain and bloating, often accompanied by a change in bowel habit with the passage of broken, pellety stools after considerable straining. All patients with such presentation should be investigated to exclude rectal or sigmoid carcinoma. Treatment is with reassurance that there is no serious underlying disease, a high-fibre diet, and—for patients with pain—antispasmodics such as mebeverine. Elective resection is indicated in the few patients who have repeated severe attacks....