Sigmoidoscopy is the minimally invasive medical examination of the large intestine through the rectum. There are two types of sigmoidoscopy: flexible sigmoidoscopy, which uses a flexible endoscope, and rigid sigmoidoscopy, which uses a rigid device. Flexible sigmoidoscopy is today generally the preferred procedure. Similar to colonoscopy, sigmoidoscopy is a very effective diagnostic tool. Sigmoidoscopy examines up to the sigmoid, the most distant part of the colon; colonoscopy examines the whole large bowel.