Flexible sigmoidoscopy is performed to view the lower colon. It is done using a sigmoidoscope, which is a flexible tube with a viewing lens and light. This procedure is used to screen or diagnose problems in the lower colon. Endoscopy is a minimally invasive diagnostic medical procedure that is used to assess the interior surfaces of an organ by inserting a tube into the body. The instrument may have a rigid or flexible tube and not only provide an image for visual inspection and photography, but also enable taking biopsies and retrieval of foreign objects. Endoscopy is the vehicle for minimally invasive surgery. The prep is not as extensive as a colonoscopy. It usually only requires a clear liquid diet and an enema.