TRUS (Transrectal Ultrasound) and Biopsy of the Prostate

If the results of a digital rectal exam, PSA test, or both suggest cancer, transrectal ultrasound is performed to determine the size of the prostate and to identify areas of possible cancer. Ultrasound also is used to direct the needles used for prostate biopsy.

A prostate biopsy typically takes about 15 to 20 minutes and is performed on an outpatient basis. Most doctors use a local anesthetic such as lidocaine (Xylocaine) to reduce discomfort during the procedure.

The ultrasound examination is performed with the man lying on his side. An ultrasound probe (about the size of a finger) is gently inserted 3 to 4 inches into the rectum. The probe emits sound waves that are converted into video images corresponding to the different prostate zones. Small prostate cancers are usually not detectable by ultrasound examination.

Fitted to the ultrasound probe is a biopsy gun with a needle that is fired through the wall of the rectum. The needle extracts small pieces of prostate tissue in less than a second. Ideally, at least 10 to 12 tissue samples ("cores") are taken from the prostate. A pathologist examines the samples under a microscope to determine whether cancer is present. If the prostate biopsy shows no cancer but the physician still suspects that cancer is present because of an abnormality on the digital rectal exam or PSA test, a repeat biopsy may be performed.

Each year, approximately 800,000 men undergo prostate biopsy. About 9 percent will be told they have high-grade prostatic intraepithelial neoplasia (PIN). Formerly called dysplasia or atypical hyperplasia, PIN is believed to be a premalignant lesion. But recent studies suggest that the likelihood of finding cancer on a repeat biopsy is no greater in men with PIN than in men with normal biopsy findings. Therefore, a finding of PIN alone is not a reason to perform a repeat biopsy.

Some prostate biopsies reveal abnormal or atypical cells that suggest the possibility of cancer but are not sufficient to make a diagnosis. In such cases, a repeat biopsy should always be performed because there is a 50 percent chance of finding cancer on that second biopsy.

A prostate biopsy usually causes only minor discomfort. Common side effects include minor rectal bleeding; blood in the stool, urine, or semen; and soreness in the biopsied area. All of these side effects disappear with time.

Additional Diagnostic Tests for Prostate Cancer

If the biopsy results indicate cancer, additional diagnostic tests will need to be conducted to determine the extent of the disease. Other routine diagnostic tests that will be performed include urinalysis and blood tests for anemia. If surgery is contemplated, general health status—particularly cardiovascular and pulmonary function—is assessed to determine whether the man is a suitable candidate for the procedure.

Publication Review By: H. Ballentine Carter, M.D.

Published: 14 Apr 2011

Last Modified: 17 Feb 2015