Prostate Ultrasound Health Article

Definition

A prostate ultrasound is a diagnostic test used to detect potential problems with a man's prostate. An ultrasound test involves very high-frequency sound waves that pass through the body. The pattern of reflected sound waves, or "echoes," shows the outline of the prostate. This test can show whether the prostate is enlarged, and whether an abnormal growth that might be cancer is present.

Purpose

The prostate is a chestnut-shaped organ surrounding the beginning of the urethra in men. It produces a milky fluid that is part of the seminal fluid discharged during ejaculation. Prostate disorders are common in men over 50. In cases of prostate cancer, ultrasound is often crucial, since early detection, when the lesion is localized and curable, can lead to effective therapy.

A doctor may decide to do a prostate ultrasound following a digital rectal examination (DRE) that reveals any prostate abnormalities such as lumps or an enlarged prostate; or following a blood test that reveals abnormal levels of a substance called prostate-specific antigen (PSA), a normal protease produced by the prostate epithelium. Currently, testing for PSA is the best available tumor marker. Abnormal levels of PSA may indicate the presence of cancer. However, the PSA test is non-specific, and PSA can be elevated without the presence of prostate cancer.

The ultrasound procedure involves a special probe inserted into the rectum that sends sound waves to the prostate gland. The waves bounce off the prostate surface and are translated by computer as an image on a screen.

If cancer is suspected, the doctor will want to take a tissue sample (prostate biopsy) to test it to see if it is cancerous. An ultrasound can show the location on the prostate from which the sample should be taken. It can also reveal if the cancer has begun to spread to other locations.

Ultrasound is also used in treatment of prostate cancer. If a doctor decides to treat the cancer with a surgical freezing procedure, ultrasound is used as an aid in the procedure. Doctors are also experimenting with a procedure that uses heat to kill cancerous prostate tissue. During this procedure, called high-intensity focused ultrasound (HIFUS), an ultrasound probe first creates an image of the prostate; then high-energy ultrasound beams target specific areas, generating heat that destroys cancerous tissue.

Ultrasound also can reveal such other types of prostate disease as prostatitis.

Precautions

A prostate ultrasound study is generally not performed on men who have recently had surgery on their lower bowel. This is because the test requires placing an ultrasound probe about the size of a finger into the rectum.

KEY TERMS

Benign prostatic hypertrophy (BPH)—An enlargement of the prostate that is not cancerous. However, BPH may cause problems with urinating or other symptoms.

Doppler—In ultrasound, a technique used to detect and evaluate moving structures that is usually applied to the evaluation of blood flowing in vessels.

Prostate-specific antigen (PSA) test—A blood test to detect PSA, a substance that is often produced by cancers of the prostate.

Urethra—The tube through which urine passes from the bladder and is excreted outside the body.

Description

The prostate ultrasound technique performed is called transrectal ultrasonography. This technique not only allows for visualization of the prostate; it is used to position the needle if a biopsy is performed. During the procedure, the cylinder-shaped ultrasound probe, or transducer, is gently placed in the rectum as the patient lies on his left side with the knees bent. This position allows for more comfort and easier insertion. The probe is rocked back and forth to obtain images of the entire prostate. Pictures of the prostate are produced and measurements are taken. The procedure takes about 15-25 minutes to perform. After the test, the patient's doctor can be notified right away, and usually he or she will have a written report within 36 hours.

During a biopsy, a small needle is inserted very rapidly into the prostate gland. Sample tissue is taken and sent to a pathology lab for preparation. Transrectal ultra-sound-guided core biopsy of the prostate is regarded as the most effective determinant of the grade, volume, and localization of a tumor and of its distribution within the prostate. Usually, six to eight biopsies are taken.

Recently, in an effort to improve prostate cancer diagnosis, physicians have performed experiments with ultrasound contrast-agent enhanced color Doppler imaging. By revealing increased vascularity associated with prostate cancer, the procedure can allow for more targeted biopsies, thus reducing the number of biopsies needed.