A flexible sigmoidoscopy exam allows a doctor to view the inside of the anus, rectum and lower third of the large intestine in order to screen for colon cancer or to evaluate intestinal symptoms, according to Mayo Clinic. The procedure lasts around 30 minutes and doesn't require sedation.
While there are no dietary or fluid restrictions required before the procedure, the patient should eat lightly prior to the examination, notes MedlinePlus. They are given an enema about an hour before the sigmoidoscopy in order to cleanse the lower colon to make the walls easier to see. Once the colon is clean, the patient lies on his left side with knees drawn up to his chest. The physician slowly passes a flexible tube affixed with a camera at the end into the rectum and gently advances it into the colon. A small amount of air may be used to inflate the colon to give a better view. The doctor examines the tissue, removes any polyps for biopsy and gently removes the instrument.
Complications of a sigmoidoscopy are minimal, according to WebMD. The most serious adverse event is a puncture of the colon which allows intestinal contents to leak into the abdomen, causing infection. The patient should contact his doctor immediately should he develop a fever with shaking chills that is accompanied by abdominal pain. Otherwise, the patient can expect to feel a bit crampy or gassy from the air introduced during the procedure, though this discomfort rapidly resolves.