Benign Prostatic Hyperplasia (BPH) vs. Prostate Cancer: The Key Role of Transrectal Ultrasound (TRUS)

Dr. Segnini
Jan 5
3 min read

Dr. Segnini Transrectal ultrasound (TRUS) prostate

Untangling Diagnosis in the Prostate Gland

The prostate is a gland that typically enlarges with age. Two main conditions cause this: Benign Prostatic Hyperplasia (BPH) , a very common non-cancerous growth, and Prostate Cancer ( PCa ) , one of the most frequent cancers in men. Both can elevate PSA (Prostate-Specific Antigen) levels and cause similar urinary symptoms. Transrectal ultrasound ( TRUS) is a fundamental tool for visualizing the prostate, guiding biopsies, and providing key information in the differential diagnosis, although it cannot, on its own, provide a definitive histological diagnosis.

Transrectal Ultrasound (TRUS): The Window to the Prostate

TRUS uses a high-frequency transducer inserted into the rectum, allowing for exceptionally detailed visualization of the prostate and seminal vesicles. Its role is multifaceted:

Morphology and Volume: Accurately measures the size and volume of the prostate (crucial for planning treatments for BPH).
Characterization of Findings: Identifies suspicious areas that could correspond to cancer.
Biopsy Guide: This is the most important and common function . It precisely guides the taking of samples (biopsies) from specific areas or systematically.
Follow-up: Monitors changes in known nodules or glandular volume.

Ultrasound Findings: Clues, Not Definitive Diagnoses

It is vital to understand that ultrasound suggests , but does not confirm , cancer. Only a biopsy can provide a definitive diagnosis.

1. Findings Suggestive of Benign Prostatic Hyperplasia (BPH):

BPH primarily affects the transitional zone (the area surrounding the urethra).

Diffuse Increase in Volume: Symmetrical and enlarged prostate, with well-defined and rounded contours .
Benign Nodules: Well-defined areas within the transitional zone, which can be:
- Isoechoic : Of the same shade of gray as normal prostate tissue.
- Hypoechoic : Darker.
- They often present associated calcifications (small bright spots), which are common and generally benign.
Retention Cysts: Small, anechoic (black), round structures without vascularization.
Prostate Stones ( Corpora) Amylacea ): Hyperechoic (bright) foci with posterior acoustic shadowing, typically in the median sulcus or transitional zone.

2. Findings Suspicious of Prostate Cancer ( PCa ):

Most cancers originate in the peripheral zone (the back and side of the gland).

Hypoechoic Nodule : A solid lesion that is darker than the surrounding normal prostatic tissue is the most classic and suspicious finding. However, not all cancers are hypoechoic , and not everything hypoechoic is cancer.
Focal Asymmetry: Loss of normal gland symmetry.
Capsule Disruption: Visualization of a lesion that appears to "blot out" or extend beyond the normal prostatic contour (suggests extracapsular extension ).
Doppler findings : Cancerous areas are often hypervascular , showing increased chaotic blood flow compared to surrounding tissue. This helps select areas for targeted biopsy.
Hyperechoic Lesions : Less frequent, but some cancers (especially those with a ductal pattern) may appear brighter.

The Star Procedure: The TRUS-Guided Prostate Biopsy

This is the standard diagnostic procedure when cancer is suspected (elevated PSA, abnormal digital rectal examination, or suspicious ultrasound finding).

Systematic Biopsy: Ten to twelve samples are taken in a standardized manner from the entire peripheral area, regardless of what is seen on the ultrasound. This is done because many cancers are isoechoic (not visible on ultrasound).
Targeted Biopsy: In addition to systematic biopsies, additional samples are taken specifically from any area that appears suspicious ( hypoechoic nodule , hypervascular area ). Image fusion (TRUS + MRI) has greatly increased the accuracy of this type of biopsy.

Limitations and the Role of Magnetic Resonance Imaging (MRI)

Main limitation of the TRUS: Low sensitivity and specificity for detecting cancer by direct imaging. Many cancers are not visible, and many visible lesions turn out to be benign on biopsy.
The Growing Role of MRI: Multiparametric prostate MRI is far superior for tissue characterization . It detects suspicious lesions with much greater accuracy ( using sequences such as diffusion and dynamic contrast). Today, the best practice is:
1. Multiparametric MRI : To identify and score suspicious lesions (according to the PI-RADS system).
2. Fusion-Guided Biopsy: Fusion of MRI images with TRUS in real time to precisely biopsy suspicious areas identified by MRI. This significantly increases the detection of clinically significant cancers.

Conclusion: A Fundamental Piece in a Diagnostic Puzzle

Transrectal ultrasound is not the perfect tool for "seeing" prostate cancer, but it is indispensable in the diagnostic process . Its true value lies in being the urologist's eyes and hands within the prostate . It provides the essential anatomical guidance for performing systematic biopsies, which, despite their limitations, remain the gold standard, and allows for sampling specific areas of concern. In the modern era, its integration with MRI (fusion biopsy) represents the gold standard for accurate diagnosis, ensuring that the most important cancers are identified, minimizing unnecessary procedures, and optimizing patient management.