How Is Ultrasound Used for Prostate Cancer?

Reviewed by: HU Medical Review Board | Last reviewed: October 2017 | Last updated: June 2020

A transrectal ultrasound, also known as TRUS, is an imaging technique used to help diagnose prostate cancer and other potential problems within the prostate. TRUS can be used on its own, or to guide needles taking tissue samples from the prostate during a biopsy.

What is TRUS used for?

TRUS can also be used to guide other treatments including brachytherapy (internal radiation) and cryotherapy.1 There are minimal, if any, risks involved in having TRUS on its own. Images are generated in real-time during TRUS, and can be used to investigate nodules (or bumps) found during a digital rectal exam, as well as to investigate the prostate gland further after a high PSA (prostate-specific antigen) test result.2,3

TRUS can also evaluate the size of the prostate gland, and the state of nearby organs to diagnose other non-cancerous conditions, such as benign prostatic hyperplasia (BPH), that may contribute to prostate cancer-related symptoms such as difficulty urinating. TRUS has been around for decades, dating back to the 1970’s and 1980’s. Today, however, TRUS used in combination with prostate biopsy is the most commonly accepted means of detecting prostate cancer.4

How does TRUS work?

Ultrasounds, including transrectal ultrasounds, rely on high frequency sound waves. These sound waves are emitted from a transducer, or a probe, and bounce off of structures within the body. The probe is connected to a computer that will generate real time images of bodily structures based on how the sound waves behave. Because the images are generated in real time, it’s possible to see blood flow and other details that X-rays would not show. The images are in black and white and can indicate abnormal growths within the prostate. Additionally, TRUS can be used to guide the needles used to collect prostate tissue samples during a prostate biopsy.2,3

The TRUS procedure

TRUS is often performed in your doctor’s office or another outpatient clinic, and when used on its own, may take only 10 minutes. TRUS on its own requires no anesthesia, but you may be numbed before the probe is inserted. The probe will be lubricated and inserted into your anus. You may have to take an enema or liquid, oral medication before the procedure to empty your bowels. During TRUS, and immediately afterward, you may feel some discomfort, but the process should not be painful at all. You can typically leave your doctors office right after the scan and can return to your normal activities immediately.

When TRUS is being used during a biopsy, anesthesia is used and the entire process may take longer. You may also need to be monitored immediately post-biopsy, and there is a risk of developing pain, bleeding or infection. Your doctor will tell you ahead of time if your TRUS will be used to guide a prostate biopsy, and what kinds of precautions are needed. Regardless of whether or not you have a biopsy at the same time as your TRUS, your doctor will let you know when to expect your results. If you do not hear from your doctor within the time frame they have given you, you can contact them to ask for an update, especially if you are experiencing anxiety while waiting for the results.2,3

Pros and Cons of TRUS

The cons of TRUS on its own are almost non-existent. The images may not be as sensitive or specific as desired at times. However, the real-time property of these images is a very important, and advantageous, aspect of TRUS. Minimal discomfort can accompany TRUS, with further risks possibly occurring when the scan is used with a prostate biopsy.

There are many benefits of TRUS, including the ability to have a real-time scan that also does not cause the individual being scanned to be exposed to radiation. This means TRUS can be repeated as often as necessary, without carrying the radiation-related risks of other imaging techniques like X-rays and MRIs. TRUS can also give a clearer picture of the prostate gland and its surrounding soft tissues and organs than with X-rays. There is very little, if any, preparation required before the scan, and you can leave right after. As mentioned earlier, TRUS can also be used to guide other treatment options such as brachytherapy (internal radiation) and cryotherapy. Additionally, TRUS can be used to determine why specific symptoms, such as difficulty urinating, are occurring in individuals who don’t have cancer.1,3

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