This is a disease process that predominantly affects people over the age of 70 years and is more common in developed countries. It is thought to be due to a relative lack of fibre or residue in the diet in middle age. As a consequence of this, the large intestine or colon may have to “squeeze” harder to move (peristalsis) the low volume stool towards the exit or rectum. Over many years the “high pressure” generated may lead to out-pouchings or pockets (diverticula) forming outside the wall of the colon, especially on the lower left side in the sigmoid colon. Many people with colonic diverticulosis are unaware of the condition. It may however lead to constipation, pain or bleeding or occasionally, the diverticulae may get infected (diverticulitis). Diverticulitis usually responds to treatment with antibiotics but sometimes it may be so severe that an abscess (collection of pus) forms or even a hole develops (perforation); these last 2 complications may require urgent surgery. It is important to confirm the diagnosis of colonic diverticulosis as its symptoms may mimic colonic cancer or colitis.