Ultrasound of the prostate

Topographic and zonal anatomy

The prostate gland surrounds the proximal urethra. It is located caudally (inferior) to the urinary bladder and ventrally (anterior) to the rectum. On the posterosuperior surface between the bladder and the rectum lie the seminal vesicles (seminal vesicles). The ejaculatory ducts pass through the thickness of the gland and open into the prostatic urethra at the level of the seminal colliculus (verumontanum). The neurovascular bundles responsible for erectile function run along the posterolateral margins.

In the craniocaudal direction (from top to bottom), the organ is conventionally divided into three levels:

1. Base (base) — the cranial portion.
2. Mid-prostate (mid-prostate).
3. Apex (apex) — the caudal portion.

The internal structure is represented by three glandular zones: the peripheral, transitional, and central zones.

TRUS in inflammatory conditions

Ultrasound examination is not a routine method for uncomplicated inflammation; however, it is mandatory when initial prostatitis treatment fails, in order to rule out abscess formation.

Acute prostatitis on ultrasound is characterized by:

• Symmetrical decrease in echogenicity in the periurethral region.
• Increased vascularity (blood flow) in the periprostatic adipose tissue.
• Multiple hypoechoic areas, predominantly localized in the peripheral zone.
• Smoothing and loss of definition of the capsular margins.

Prostatic abscess (as a late complication) in the early stages appears as a heterogeneous or completely anechoic formation with small internal echoes. As it progresses, its margins become irregular. Without treatment, the abscess can disrupt the capsule or spontaneously rupture into the urethra, rectum, or surrounding tissue. TRUS also serves as a guidance method during abscess drainage.

Ultrasound guidance and biopsy in suspected cancer

Prostate cancer (PCa) is one of the most common oncological diseases in men. High-risk signs include abnormalities on digital rectal examination and an elevated prostate-specific antigen (PSA) level. However, PSA has low specificity: 70–80% of patients with a level above 4.0 ng/mL are found to have benign prostatic hyperplasia (BPH) or inflammation rather than cancer.

When PCa is suspected, the patient is indicated for a TRUS-guided biopsy. The method allows for multiplanar angled access and real-time monitoring of needle movement.

Limitations of standard TRUS biopsy:

• The method is highly dependent on the operator's skill (operator-dependent).
• High risk of sampling errors due to tumor heterogeneity and multifocality.
• Traditional "blind" sampling of 10–12 cores may miss an aggressive high-risk tumor (underdiagnosis) or, conversely, detect indolent cancer that does not require treatment (overdiagnosis).

To overcome these shortcomings, fusion imaging technologies are used. The physician overlays pre-acquired MRI scans onto the real-time ultrasound image, allowing precise needle insertion into a focus that is invisible on conventional ultrasound.

Class and exam questions

What else to study on this topic

• Magnetic resonance imaging in PCa staging
• Specific MRI sequences for prostate evaluation
• Limitations of PSA screening and the problem of PCa overdiagnosis
• Molecular markers: prostate health index and 4Kscore
• Application of CT in assessing extracapsular spread of an abscess

Other topics in the section "Diagnostic Radiology of the Abdominal Organs"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.