A prostate ultrasound is a painless imaging test that employs sound wave energy to visualize the prostate gland. Your doctor may order this test to help diagnose an enlarged prostate, fertility issues or prostate cancer. Alternatively, the test may be used to stage or evaluate the ongoing treatment of prostate cancer, or to help in the precise placement of a needle for purposes of a biopsy. It may also be employed to assist in the implantation of radiation “seeds” used in treating cancer. Patients are directed to administer an enema while at home approximately two hours before the test. In this type of ultrasound, a small and lubricated transducer is inserted into the rectum where it emits sound waves to visualize the prostate on a computer screen. The entire procedure usually takes just over half an hour.