Scrotal Ultrasound 

Infections & Inflammations in the Scrotum

"Scrotal ultrasound is one of those examinations where minutes matter, patterns decide management, and Doppler can save a testis. From sudden scrotal pain at 2 a.m. to chronic nodular swellings that mimic tumors, ultrasound is the frontline tool that separates emergencies from reassurance"

1. Acute Scrotum – When the Alarm Bells Ring “Sudden pain, swelling, redness? Ultrasound to the rescue!” What is Acute Scrotum? Acute scrotum refers to sudden onset scrotal pain with or without swelling, requiring urgent evaluation. The goal of ultrasound is simple:

Is this surgical… or medical?

• Testicular torsion – surgical emergency
• Epididymo-orchitis – medical treatment
• Infarction or abscess – complication of infection
• Trauma – hematoma or rupture
• Tumor – usually painless but critical to detect
• Fournier’s gangrene – life-threatening infection

1. Grayscale (B-mode): Size, echotexture, collections
2. Color Doppler: Vascularity – the real decision maker
3. Spectral Doppler: RI, flow direction, resistance

• Testicular Inferno: Marked hyperemia → orchitis
• Whirlpool sign: Twisted spermatic cord → torsion
• To-and-fro flow: Compromised perfusion
• Dirty shadowing: Gas → Fournier’s gangrene
• Segmental avascular hypoechoic area: Infarct or abscess

• Hypervascularity with low resistance: Acute inflammation
• Absent intratesticular flow: Torsion or complete infarction
• High-resistance flow (RI > 0.8): Impending infarction
• Flow reversal / to-and-fro: Severe venous congestion

• Normal testis: RI ~0.6–0.7
• Inflammation: Low RI, high velocity
• Vascular compromise: High RI, low velocity
• Necrosis: Absent or oscillating flow
  3. Epididymo-Orchitis – The Stepwise Progression Infection doesn’t jump straight to the testis.
  It climbs step by step. Pathophysiological Journey Vasitis → Funiculitis → Epididymitis → Epididymo-orchitis Early Sonographic Features
  • Bulky, hypoechoic epididymis
  • Mildly enlarged heterogeneous testis
  • Marked hyperemia (Testicular Inferno)
  • Reactive hydrocele
  Complicated Epididymo-Orchitis
  • Segmental infarction: Wedge-shaped, avascular area
  • Global infarction: Enlarged testis, no flow
  • Abscess: Avascular center + rim hyperemia
  • Pyocele: Septated infected hydrocele
  Mnemonic for Orchitis Complications – “FIRMS”
  • Fibrosis
  • Infarction
  • Rupture (rare)
  • Microabscess / Abscess
  • Secondary tumor unmasking
    4. Torsion vs Epididymo-Orchitis – The Classic Battle

    Feature	Torsion	Epididymo-orchitis
    Pain	Sudden, severe	Gradual
    UTI history	No	Common
    Cremasteric reflex	Absent	Present
    Prehn’s sign	Negative	Positive
    Cord	Twisted, avascular	Thick, hyperemic
    Doppler	Absent / high RI	Hyperemia
    Testis lie	Horizontal	Normal

    🚩 Whirlpool sign = Torsion
    🔥 Inferno = Infection
    
  5. The Detorsion Trap Sometimes torsion self-corrects before imaging. What You See:
  • Patient pain-free on arrival
  • Testis mildly enlarged
  • Increased Doppler flow (rebound hyperemia)
  ⚠️ This is NOT orchitis.
  🧠 Clue: Sudden pain + sudden relief = detorsion.
  6. Infarction – Segmental vs Global Segmental Testicular Infarction
  • Wedge-shaped hypoechoic area
  • No internal vascularity
  • Surrounding reactive flow
  • Testis otherwise normal
  Key tip:

  Orchitis affects diffusely.
  Infarction respects a wedge.

  Global Testicular Infarction
  • Entire testis enlarged, hypoechoic
  • No color flow
  • Very high RI (>0.9) before complete shutdown
  Causes:
  • Missed torsion
  • Severe orchitis
  • Venous thrombosis
  7. Abscess, Pyocele & Fournier’s Gangrene Testicular / Epididymal Abscess
  • Hypoechoic or cystic lesion
  • Avascular center
  • Hyperemic rim
  Pyocele
  • Septated echogenic fluid
  • Internal debris
  • Often post-abscess or severe infection
  Fournier’s Gangrene – Don’t Miss It
  • Subcutaneous gas → dirty shadowing
  • Thickened scrotal wall
  • Testis often spared (separate blood supply)
  Ultrasound is excellent for early diagnosis, CT for extent.
  

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