Flexible sigmoidoscopy is usually performed on an outpatient basis. It is performed with the patient lying on the left side with the legs drawn up. A sheet is placed over the lower body. A finger or digital exam of the anus and rectum is performed. Then the endoscope is gently inserted into the rectum. Air is inflated into the bowel to expand it and allow for careful examination. The patient usually feels a slight discomfort similar to strong gas cramps. The endoscope is then advanced under direct vision and moved around the various bends in the lower bowel.

It is advanced as far as possible without causing undue discomfort. When possible, the exam is continued to 60 cm. Certain conditions, such as diverticulosis, irritable bowel syndrome, or prior pelvic surgery may produce discomfort when the sigmoid colon is entered by the endoscope. The exam is stopped if this occurs. The exam usually takes 5 to 15 minutes. Sedation is not normally required.