Prostate Symptoms and Ultrasound: What a Scan Can Detect

Lower urinary tract symptoms (LUTS) affect approximately 30% of men over 50 and include a range of storage symptoms (frequency, urgency, nocturia) and voiding symptoms (hesitancy, poor flow, incomplete emptying, terminal dribbling). LUTS are most commonly caused by benign prostatic hyperplasia (BPH), but can also result from bladder overactivity, urinary tract infection, bladder stones, or — less commonly — prostate or bladder cancer.

NICE guideline NG123 on LUTS in men recommends that all men presenting with LUTS should have a clinical assessment including a digital rectal examination (DRE), PSA test, urinalysis, and measurement of post-void residual urine. Ultrasound provides the post-void residual measurement and prostate volume assessment that are central to this workup.

The prostate is measured in three dimensions (length, width, and height) and the volume is calculated using the prolate ellipsoid formula (length × width × height × 0.52). A prostate volume above 30 ml is considered enlarged; above 80 ml is associated with significant obstruction and is relevant to treatment planning for surgical intervention.

Benign prostatic hyperplasia (BPH) is the most common cause of LUTS in men over 50. It is a histological diagnosis — the definitive diagnosis requires tissue — but ultrasound-measured prostate volume is used as a surrogate marker in clinical practice. A prostate volume above 30 ml in a man with LUTS is consistent with BPH and guides treatment decisions.

"Prostate volume measured by ultrasound is the key parameter that determines whether medical treatment or surgical intervention is more appropriate for BPH."

5-alpha reductase inhibitors (such as finasteride and dutasteride) are most effective in men with prostate volumes above 40 ml. Alpha-blockers (such as tamsulosin) provide symptom relief regardless of prostate size. For men considering surgical options (TURP, HoLEP, or UroLift), prostate volume is a key factor in procedure selection.

Post-void residual (PVR) urine volume — the amount of urine remaining in the bladder after voiding — is measured by ultrasound immediately after the patient has urinated. A PVR below 50 ml is considered normal; 50–300 ml is equivocal and requires clinical correlation; above 300 ml indicates significant urinary retention requiring urgent urological assessment.

Chronic urinary retention with a high PVR can lead to recurrent urinary tract infections, bladder stones, upper tract dilatation (hydronephrosis), and — in severe cases — renal impairment. Early identification of a high PVR at our Weymouth Street clinic allows prompt referral before these complications develop.

PSA (prostate-specific antigen) is a blood test that measures a protein produced by prostate cells. An elevated PSA can indicate BPH, prostatitis, or prostate cancer, but it is not specific for cancer — approximately 75% of men with an elevated PSA do not have prostate cancer. Ultrasound provides structural information that PSA cannot: gland volume, echogenicity, and the presence of suspicious lesions.

Transabdominal ultrasound of the prostate is a useful screening tool for gland volume and bladder function, but it does not replace transrectal ultrasound (TRUS) or MRI for prostate cancer assessment. If PSA is elevated or a suspicious lesion is identified, referral for multiparametric MRI (mpMRI) is the appropriate next step in line with NICE guideline NG131.

Men with LUTS who have any of the following features require prompt further investigation: haematuria (blood in urine), recurrent urinary tract infections, palpable bladder, neurological symptoms, or a PSA above the age-specific threshold. These features may indicate bladder cancer, prostate cancer, or neurogenic bladder dysfunction rather than simple BPH.

At our HCPC Registered clinic in Central London, our sonographers are trained to identify incidental findings — such as bladder wall irregularity, echogenic lesions within the prostate, or upper tract dilatation — that require urgent onward referral. All findings are documented in the written report provided within 24 hours.