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Transrectal ultrasound (TRUS)

A transrectal ultrasound (TRUS) is an ultrasound technique that is used to view a man’s prostate and surrounding tissues. The ultrasound transducer (probe) sends sound waves through the wall of the rectum into the prostate gland, which is located directly in front of the rectum. TRUS may also be called prostate sonogram or endorectal ultrasound.

Why a TRUS is done

A TRUS may be done to:

  • determine if the prostate is enlarged
  • diagnose prostate cancer
    • TRUS is done if the doctor suspects cancer because of an increased prostate-specific antigen (PSA) level, abnormalities felt during digital rectal examination (DRE) or certain symptoms are present, such as problems with urination.
  • help guide the doctor when taking biopsy samples of the prostate
  • help diagnose the cause of infertility in a man
  • help guide the doctor during treatments for prostate cancer

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How a TRUS is done

A TRUS is usually done as on outpatient procedure in a doctor’s office, clinic or hospital. The test usually takes 15–30 minutes.

  • Some special preparation is needed before a TRUS.
    • Avoid taking Aspirin and other medications that may thin the blood for 7–10 days before the test.
    • An enema is used 1–4 hours before the procedure to help clean out the colon.
    • The man may be told to urinate to empty his bladder just before the procedure.
  • The man wears a gown during the procedure. He usually lies on his left side with his knees bent toward the chest.
  • A protective cover and lubricant are put on the ultrasound transducer (probe), then it is placed into the rectum.
  • The man may feel pressure or have a sensation of fullness in the rectum when the transducer is in place.
  • The transducer directs high-frequency sound waves at the prostate
  • A computer analyzes the echoes created by the sound waves and displays an image of the prostate gland on a monitor.
  • The image shows how big the prostate is and whether there are any abnormalities.

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Prostate biopsy using TRUS

Doctors can use TRUS to guide a biopsy needle to an abnormal area to collect a sample of cells or tissues. The prostate tissue is then examined under a microscope to determine if cancer is present.

  • The doctor inserts a needle next to the ultrasound probe.
  • The needle is pushed through the wall of the rectum into the prostate.
    • A brief, sharp pain may be felt during this part of the procedure.
    • Local anesthetic may be used numb the biopsy area and reduce discomfort.
  • The doctor uses the needle to collect samples of prostate tissue.
    • Samples are taken from areas that look suspicious on the ultrasound.
    • Other areas of the prostate are also sampled.
    • Typically, 6–12 samples are taken.

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Potential side effects

Side effects can occur with any type of procedure, but not everyone has them or experiences them in the same way. Most side effects of TRUS occur when it is used to collect a prostate biopsy. Side effects are short term and may include:

  • There may be a small amount of bleeding from the rectum for a few days after a prostate biopsy using TRUS.
  • The biopsy sites may be tender or sore for a few days.
  • For a few weeks after a prostate biopsy, a man may notice bright red or dark brown blood in his urine or semen.
  • Antibiotics can reduce the risk of infection. The doctor may prescribe antibiotics before and after a prostate biopsy. It is important that men see their doctor if they develop a fever within a few days of the procedure.
  • In rare cases, a man might have difficulty urinating after a prostate biopsy because of swelling of the prostate. This side effect is usually temporary.

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What the results mean

Abnormal findings may include:

If TRUS shows abnormal areas but no cancer is found in the biopsy sample, a transrectal needle biopsy may need to be repeated. The procedure may be done again in 6–12 months if:

  • the suspicious area of the prostate is still present or growing
  • the PSA level increases
  • precancerous cells were found in the first biopsy

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What happens if a change or abnormality is found

The doctor will decide whether further tests, procedures, follow-up care or additional treatment is needed.

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