Colonic diverticula. Endoscope view of three diverticula (pouches, upper centre) in the wall of the sigmoid colon, the part of the large intestine which joins to the rectum. Diverticula are small pouches in the lining of the colon. Their format- ion is thought to be linked to a low-fibre diet and they are very common in the elderly. Usually they cause no symptoms, although some may cause abdominal cramps and constipation or diarrhoea.