Diverticulosis of the colorectum predominantly occurs on the left side of the colon or the rectum. It consists of multiple pouches or diverticulae, which in essence are herniation of the colorectal mucosa through weakness in the muscular wall of the bowel. The aetiology is high luminal pressure coupled with excessive peristalsis, as a result of low fiber diet of modern society.

Diverticulosis is extremely common in the west but curiously is not very common among Chinese. The disease manifests as GI bleeding, inflammation or GI obstruction.