What is Prehn sign?

Prehn's Sign: Clinical Utility in Acute Scrotal Pain

Prehn's sign refers to the relief of scrotal pain when the scrotum is elevated (lifted), which is typically positive in epididymitis and negative in testicular torsion. 1

Definition and Clinical Significance

Prehn's sign is a physical examination finding used to help differentiate between causes of acute scrotal pain:

• Positive Prehn's sign: Pain is relieved when the scrotum is elevated over the symphysis pubis

  • Typically seen in epididymitis
  • Suggests inflammatory etiology 1

• Negative Prehn's sign: Pain persists or worsens with scrotal elevation

  • Suggests testicular torsion
  • Indicates possible surgical emergency 1, 2

Diagnostic Value

The diagnostic utility of Prehn's sign has important limitations:

• Low sensitivity: Recent evidence shows Prehn's sign can be positive in 10.5-100% of confirmed testicular torsion cases, making it unreliable for ruling out torsion 2
• Limited specificity: A positive Prehn's sign increases the likelihood of epididymitis but cannot definitively rule out torsion 3
• Clinical context: Must be interpreted alongside other findings, not as a standalone test 1

Integration with Other Clinical Findings

When evaluating acute scrotal pain, Prehn's sign should be considered with:

1. Onset characteristics:

   • Sudden, severe pain suggests torsion
   • Gradual onset suggests epididymitis 1

2. Associated symptoms:

   • Fever, dysuria, and burning pain favor epididymitis
   • Absence of urinary symptoms favors torsion 3

3. Laboratory findings:

   • Elevated WBC count and CRP suggest infection/epididymitis
   • Normal laboratory values don't exclude torsion 3

Imaging Correlation

Prehn's sign should never delay appropriate imaging:

• Ultrasound with Doppler is the first-line imaging modality for acute scrotal pain 1
• Absent or decreased blood flow suggests torsion
• Increased blood flow suggests epididymitis 1

Important Caveats

• False reassurance risk: A positive Prehn's sign does not definitively rule out testicular torsion 2
• Time sensitivity: Testicular salvage rates decrease significantly after 6-8 hours of torsion 1
• Age consideration: Torsion has a bimodal distribution (neonates and postpubertal boys) but can occur at any age 1

Clinical Bottom Line

While Prehn's sign can provide helpful clinical information in the evaluation of acute scrotal pain, it should never be used in isolation to rule out testicular torsion. When torsion cannot be confidently excluded based on the complete clinical picture and imaging, surgical exploration remains mandatory to preserve testicular viability and function.