Male Pelvic Imaging

Male Pelvic Anatomy & Modalities - Pixel Perfect Pelvis

• Key Structures & Zones:
  • Prostate: Peripheral (PZ - commonest cancer site), Central (CZ), Transitional (TZ - BPH site).
  • Seminal Vesicles (SVs), Vas Deferens, Ejaculatory Ducts.
  • Bladder, Urethra, Rectum.
• Primary Imaging Modalities:
  • USG: TRUS for prostate (biopsy, volume); TAUS for bladder.
  • MRI: Best soft tissue. Multiplanar.
    • Prostate: T2WI (zonal anatomy), DWI (malignancy), DCE (vascularity). PI-RADS (1-5).
    • Local staging: prostate, rectal, bladder cancers.
  • CT: Trauma, bony pelvis, calcifications, gross nodal/distant mets.
  • Fluoroscopy: RGU/VCUG for urethral strictures, VUR.

⭐ On T2-MRI, prostate cancer in PZ often appears as a low signal intensity focus.

Prostate Gland Imaging - Gland Central Station

• Modalities:
  • Transrectal Ultrasound (TRUS): Biopsy guidance, initial assessment.
  • Multiparametric MRI (mpMRI): Gold standard for detection, staging, and active surveillance of prostate cancer. Sequences: T2W, DWI, DCE.
  • CT: Limited for primary tumor; useful for nodal/metastatic disease.
• Zonal Anatomy (T2W MRI):
  • Peripheral Zone (PZ): ~70% cancers. High T2 signal.
  • Transition Zone (TZ): BPH origin. Heterogeneous T2 signal.
  • Central Zone (CZ): Low T2 signal.
  • Anterior Fibromuscular Stroma (AFMS): Very low T2 signal.
• Prostate Cancer on mpMRI:
  • PZ: T2 hypointense, restricted diffusion (low ADC), early enhancement.
  • TZ: More challenging; ill-defined, homogenous, T2 hypointense, lenticular.
• PI-RADS (Prostate Imaging Reporting and Data System):
  • Standardized reporting for cancer risk (Score 1-5).
  • Dominant sequence: PZ (DWI), TZ (T2W).

⭐ Most prostate cancers (~70-80%) arise in the Peripheral Zone (PZ).

Testicular & Scrotal Imaging - Testicular Tales

• Ultrasound (USG): Primary modality. High-frequency linear probe (7.5-12 MHz).
  • Normal Testis: Homogeneous, mid-grey. Size: 3-5 cm (L). Volume: ~20 ml.
  • Color Doppler: Crucial for vascularity.
• Key Conditions:
  • Testicular Torsion:
    • Acute pain.
    • USG: Enlarged, hypoechoic testis. ↓/absent Doppler flow. Whirlpool sign of cord.
    • ⚠️ Surgical emergency: salvage ↓ after 6 hrs.
  • Epididymo-orchitis:
    • Pain, fever.
    • USG: Enlarged epididymis &/or testis. ↑ Doppler flow. Reactive hydrocele.
  • Varicocele:
    • Dilated pampiniform veins (>2-3 mm), ↑ with Valsalva. Usually left.
  • Hydrocele:
    • Anechoic fluid in tunica vaginalis.
  • Testicular Tumors:
    • Seminoma: Hypoechoic, homogeneous.
    • NSGCT: Heterogeneous.
    • Markers: AFP, β-hCG.

⭐ "Bell-clapper" deformity, where the tunica vaginalis has an abnormally high attachment to the spermatic cord, is a major predisposing factor for testicular torsion.

Penile & Urethral Pathologies - Pointing Out Problems

• Penile Pathologies:
  • Peyronie's Disease: Fibrous plaques (tunica albuginea) → penile curvature. USG: calcified plaques.
  • Priapism: Erection >4 hrs. Doppler USG: Ischemic (low flow) vs. Non-ischemic (high flow).
  • Penile Fracture: Tunica albuginea rupture. "Eggplant deformity". USG/MRI. RGU if urethral injury suspected.
  • Penile Cancer (SCC): MRI for local staging, inguinal node assessment.
• Urethral Pathologies:
  • Urethral Strictures: Fibrotic narrowing. RGU/VCUG (MCU) for diagnosis, location, length.
  • Urethral Trauma:
    • Anterior: Straddle injury. RGU.
    • Posterior: Pelvic fracture. 📌 "High-riding prostate".
  • Urethral Diverticula: Outpouching. VCUG/RGU, MRI.
  • Urethral Cancer (SCC): Rare. RGU, MRI for staging.

⭐ Posterior urethral injury (pelvic fracture): "High-riding prostate" on imaging due to hematoma. RGU often deferred or performed with caution after initial stabilization (e.g., suprapubic catheter).

High‑Yield Points - ⚡ Biggest Takeaways

• MRI is gold standard for prostate cancer staging (TNM) and local recurrence detection.
• TRUS is key for prostate biopsy guidance and evaluating male infertility (e.g., ejaculatory duct obstruction).
• Testicular torsion: Color Doppler US shows absent testicular blood flow - a surgical emergency.
• Varicocele: Ultrasound with Valsalva identifies dilated pampiniform plexus veins (>2-3mm).
• Zinner syndrome: Triad of seminal vesicle cyst, ejaculatory duct obstruction, ipsilateral renal agenesis.
• RGU/MCU are crucial for evaluating urethral injuries, especially post-trauma.