Transrectal ultrasoun uses inaudible sound waves produced by a probe inserted into the rectum to create an image of organs in the pelvis. The most common indication for transrectal ultrasound is for the evaluation of the prostate gland in men with elevated prostate specific antigen or prostatic nodules on digital rectal exam. Ultrasound may reveal prostate cancer, benign prostatic hypertrophy, or prostatitis. Ultrasound may also be used to help guide a biopsy of the prostate.