A transrectal ultrasound of the prostate typically involves a sono-exam in which an ultrasound probe is inserted into the rectum of the patient in order to observe and evaluate the prostrate.  The probe essentially sends and receives sound waves through the rectum into the prostate gland.  This procedure is performed on a regular basis for men who have felt lumps in the area of the prostate, who may have an enlarged prostrate, or to detect for prostate diseases and abnormalities.