What it is (overview)

A Prostate Transrectal Ultrasound (TRUS)—also called a transrectal ultrasound of the prostate—is a type of diagnostic imaging test that uses sound waves to create real-time pictures of the prostate gland. Because the prostate sits directly in front of the rectum, the ultrasound probe is gently placed into the rectum (similar in position to a rectal examination) to get clear, detailed images.

This test helps your clinician assess the size, shape, and structure of the prostate. It can also identify areas that look different from surrounding tissue and can be used for biopsy guidance—meaning it helps accurately guide a needle to take small tissue samples when prostate cancer is suspected.

What it measures / evaluates typically includes:

• Prostate size (volume), which can be helpful when assessing prostate enlargement (BPH) and planning treatment.
• Abnormal-appearing areas such as nodules, asymmetry, calcifications, cysts, or areas that may need closer evaluation.
• Changes over time if you are being monitored for known urology issues.
• Targeting for prostate biopsy (often TRUS-guided biopsy) to sample suspicious regions.

What the results mean in plain language: A TRUS report may describe the prostate’s volume, whether it looks enlarged, and whether there are any areas that appear suspicious or abnormal. Importantly, an ultrasound image alone usually cannot confirm or rule out cancer. If suspicious features are seen—or if your PSA levels or exam findings are concerning—your clinician may recommend a biopsy or additional tests (such as an MRI) to clarify the cause.

When & why it's usually done

A prostate transrectal ultrasound is commonly ordered by a urology specialist or primary care clinician when there are symptoms, exam findings, or lab results suggesting a prostate problem. It is also frequently performed specifically for prostate biopsy guidance.

Your doctor may recommend a transrectal ultrasound if you have:

• Elevated or rising PSA (prostate-specific antigen) blood test results.
• An abnormal digital rectal exam (DRE), such as a lump, firmness, or asymmetry.
• Symptoms of prostate enlargement (BPH), including slow urine flow, difficulty starting urination, frequent urination (especially at night), urgency, or incomplete emptying.
• Unexplained blood in the urine or blood in semen.
• Persistent pelvic/perineal discomfort or suspected prostatitis (inflammation/infection), depending on your overall evaluation.
• Need for accurate measurement of prostate size to help guide treatment choices (for example, selecting medications or planning procedures).

It may also be done due to risk factors for prostate cancer or prostate disease, such as increasing age, a strong family history of prostate cancer, or certain ancestry-related risk patterns. TRUS is a practical, widely available test in men’s health care because it provides real-time images and can be performed in an outpatient setting.

Common diseases related to it

• Benign prostatic hyperplasia (BPH) (non-cancerous prostate enlargement)
• Prostate cancer
• Prostatitis (acute or chronic inflammation/infection)
• Prostate nodules or suspicious lesions found on rectal examination
• Prostatic cysts
• Prostatic calcifications (stones/calcium deposits)
• Lower urinary tract obstruction related to prostate enlargement

Health goals where it may help

• Early detection and evaluation of prostate cancer when PSA or exam findings are concerning
• Guiding a prostate biopsy to improve sampling accuracy of suspicious areas
• Monitoring prostate enlargement (BPH) and supporting treatment planning
• Improving urinary health by clarifying prostate-related causes of urinary symptoms
• Supporting men’s health screening decisions in discussion with a clinician (PSA, DRE, and imaging when appropriate)
• Tracking prostate changes over time for ongoing urology follow-up