Transrectal Ultrasound

A minimally invasive ultrasound exam to assess prostate health

Transrectal ultrasound, or TRUS, is an imaging technique that uses a small ultrasound probe inserted into the rectum to visualize pelvic organs, most commonly the prostate in men, as well as the seminal vesicles, rectal wall, and surrounding tissues. It’s typically employed when cancer is suspected.

Transrectal ultrasound (TRUS) is an imaging procedure that uses high-energy sound waves to create real-time images of the prostate gland and surrounding structures. The sound waves bounce off tissues, and the echoes are converted into images called sonograms. TRUS is sometimes called a prostate ultrasound, endorectal ultrasound (ERUS), or prostate sonography.

TRUS is most often performed to evaluate the size, shape, and internal structures of the prostate. Because of the probe’s proximity to the prostate, TRUS provides detailed imaging that cannot be achieved with external ultrasound. It is considered a cornerstone tool in urology, particularly for evaluating prostate anatomy, detecting abnormalities, and guiding biopsies.

While it can identify abnormalities, it cannot definitively diagnose cancer. When cancer is suspected, the ultrasound is used to guide a needle biopsy, allowing small samples of prostate tissue to be collected for laboratory analysis. The procedure can be done in a doctor’s office, outpatient clinic, or hospital with light sedation and local anesthesia.

Why is a Transrectal Ultrasound Recommended?

TRUS is used for both cancer-related and non-cancerous conditions. Cancer-related reasons include:

Elevated PSA (prostate-specific antigen)
Abnormal digital rectal exam (DRE), such as a hard nodule
Suspicion of prostate cancer
Guidance for prostate biopsy (most common use)
MRI-targeted or fusion biopsy planning
Monitoring known prostate cancer or guiding treatment
Calculating prostate volume and PSA density

Non-cancerous conditions for recommending TRUS include:

Benign prostatic hyperplasia (BPH) – BPH is very common, affecting about 80% of men by the time they’re 70.1 TRUS helps measure prostate size and guide treatment decisions.
Prostatitis (inflammation/infection) – TRUS can show increased blood flow, edema, or structural changes.
Prostatic abscess – These abrasions appear as fluid-filled cavities, and TRUS can also help guide drainage.
Persistent hematospermia (blood in semen) – TRUS is used to evaluate the prostate and seminal vesicles for structural abnormalities such as cysts, inflammation, ductal obstruction, or rare malignancy.
Male infertility evaluation – TRUS helps assess structures involved in semen production and transport, including the seminal vesicles and ejaculatory ducts. It can identify blockages, cysts, or congenital abnormalities that may impair sperm delivery rather than production.
Lower urinary tract symptoms – Weak stream, urinary retention, or obstruction are often related to prostate enlargement (BPH). TRUS helps measure prostate size, assess how the gland compresses the urethra, and identify features such as median lobe enlargement that can mechanically block urine flow.
Anatomical evaluation before surgery or treatments – TRUS precisely measures prostate size, shape, and spatial relationships to nearby structures, which can be used to guide procedural planning and determine candidacy for specific treatments.
Guidance for procedures – TRUS improves accuracy, minimizes damage to surrounding structures, and allows continuous visualization during treatment. Synchronicity in guiding instruments is achieved in such cases as:
- Aquablation for (BPH), where the ultrasound maps prostate tissue so water-jet ablation can be precisely targeted
- Cryotherapy, in which TRUS ensures freezing probes are accurately placed within the prostate
- HIFU (high-intensity focused ultrasound), where TRUS helps localize and monitor targeted tissue destruction

What Can Patients Expect Before, During, and After the Procedure?

Minimal prep is required prior to the transrectal ultrasound. Beforehand, your physician will review your medical history, medication use, and ask about any allergies (especially to antibiotics and anesthesia). A digital rectal exam is also typically part of the evaluation. If a biopsy is planned, patients will need to stop taking blood thinners, and an enema may be given to clear the rectum.

Antibiotics are commonly given a few days before and after a biopsy procedure, since the biopsy needle passes through the rectal wall, which is naturally colonized with bacteria. This can introduce bacteria into the prostate or bloodstream, increasing the risk of complications like urinary tract infection, prostatitis, or, in rare cases, sepsis. Prophylactic antibiotics have been shown to significantly lower these post-procedure infectious complications.

During the procedure, patients will lie on their left side with their knees bent. A lubricated probe approximately the same size as the circumference of a U.S. penny is inserted into the rectum, and the sensation most patients report is a pressure similar to needing a bowel movement. The prostate is then scanned on multiple planes to assess size, shape, symmetry, and abnormalities. Advanced imaging may also be used to investigate blood flow (Doppler), tissue stiffness (elastography), or vascular patterns (contrast ultrasound).

If a biopsy is being performed, local anesthesia in the form of a nerve block plus rectal gel is used. A spring-loaded needle takes multiple samples (“cores”), and each core only takes a split second. The TRUS guides the needle placement.

The ultrasound alone may take about 10 to 15 minutes, and with biopsy, the procedure may take 20 to 30 minutes. Patients are typically clear to go home afterward and resume normal activities, unless a biopsy was performed, in which case downtime could be 2 to 7 days to allow the prostate to heal and minimize bleeding risks.

Common temporary effects, especially after a biopsy, can include blood in urine, stool, or semen; mild soreness or discomfort; and fatigue. Less common risks include infection or urinary retention.

What Do the Results Mean?

TRUS evaluates prostate size and volume, shape and symmetry, and echogenicity (how the tissue reflects sound). In doing that, possible imaging findings include BPH, prostatitis, abscess, and suspicious lesions. TRUS cannot reliably distinguish cancer from benign tissue, and up to 40% of cancers may not appear clearly abnormal.¹ This is why multiple modalities are employed to evaluate potential malignancy.

If a biopsy is performed, the tissue is analysed by a pathologist and the results take a few days to a week. Indeterminate findings may need a repeat biopsy or MRI. If cancer is detected, it will be graded using a Gleason score. This is a system used to grade prostate cancer aggressiveness based on how abnormal cancer cells look under a microscope, with higher scores indicating faster-growing, more aggressive cancer.

With normal results, patients just need to keep up with regular check-ups and screenings. If cancer is confirmed, the next step will be a discussion with your urologist about potential therapies, including active surveillance, surgery, radiation, NanoKnife, and other therapies or combinations of therapies.

TRUS is often just one step in a larger diagnostic pathway, not the final answer. At Georgia Urology, we treat the full spectrum of men’s urologic conditions. Whether you’re dealing with prostate issues, erectile dysfunction, urinary incontinence, or any other urologic condition, our experts are here to provide the highest quality of care. We stay abreast of the research coming down the pipeline so our patients are in the know about every option available to them.

Contact our team at Georgia Urology to schedule an appointment. Whatever you do, don’t let something treatable now become a bigger problem down the road.

FAQs

Is TRUS painful?

Usually not. Most patients report pressure that is uncomfortable. Biopsy adds brief, sharp sensations.

Can TRUS diagnose prostate cancer by itself?

No. It helps guide a biopsy, but cannot confirm the presence of cancer.

Why not just use MRI instead?

MRI is better at detecting suspicious areas, but TRUS is more accessible and is still widely used for performing real-time biopsies.

Why are antibiotics needed?

For infection prevention, because the probe and needle pass near bacteria in the rectum.

How many samples are taken in a biopsy?

Typically about 12, sometimes more, depending on prostate size or suspicion.

Will it affect sexual function?

TRUS alone: no. Biopsy: temporary erectile dysfunction can occur in some patients and usually resolves within one to three months, though there are instances in which it may take up to six months to fully return to baseline.1

Resources:

Jones, S., & Carter, K. R. (2025, December 9). Transrectal Ultrasonography and Image-Guided Biopsies of the Prostate. PubMed; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK570569/.

This page was reviewed by Ronald Anglade, MD

Dr. Anglade is a native of New York. He received his undergraduate degree from Brown University, Providence, RI. He then returned to New York and received his medical degree from the State University of New York Health Science Center at Brooklyn (Downstate Medical Center).

Schedule an Appointment