During a residency, a Senior Doctor will teach a Resident how to perform a rectal exam. This procedure is a diagnostic tool used to detect cancer in the prostate. It involves inserting a thin tube with a balloon on the end into the rectum. The catheter has pressure sensors placed below it. As the tube is pulled back through the anal canal, the pressure sensors will measure how hard the muscles are. This test does not require any anesthesia and takes 30 minutes..