What is the Prehn sign and how is it used to differentiate epididymitis from testicular torsion in a patient with acute scrotal pain?

Prehn Sign in Acute Scrotal Pain

Definition and Clinical Application

Prehn sign is the relief of testicular pain upon elevation of the scrotum, traditionally taught to differentiate epididymitis (positive sign = pain relief) from testicular torsion (negative sign = no pain relief or worsening pain), but recent evidence demonstrates this sign is unreliable and should not be used to rule out testicular torsion. 1

Evidence Against Clinical Utility

The most recent systematic review (2025) examining Prehn sign's diagnostic accuracy found critical limitations that render it clinically unreliable 2:

• In patients with confirmed testicular torsion, Prehn sign was positive (pain relief with elevation) in 10.5% to 100% of cases across different studies, meaning the negativity ranged from 0% to 89.5% 2
• One study found 33% of testicular torsion patients had a positive Prehn sign, with an odds ratio of 5.941 (95% CI 1.432 to 24.658) 2
• The sign is insufficiently sensitive to rule out testicular torsion; however, when negative (no pain relief), it actually increases the likelihood of torsion diagnosis 2

Why Prehn Sign Fails Clinically

The fundamental problem is that testicular torsion can present with a positive Prehn sign in up to 37.5% of cases, making it dangerously misleading 2. This occurs because:

• Reactive hydrocele can develop with torsion, potentially providing temporary relief with elevation 1
• Severe scrotal edema distorts physical examination findings 1
• The degree of torsion affects symptom presentation—partial torsion may have atypical features 1

Reliable Clinical Distinguishing Features

Instead of relying on Prehn sign, use these evidence-based discriminators 1:

Testicular Torsion:

• Abrupt onset of severe scrotal pain 1
• Younger age (bimodal distribution: neonates and postpubertal boys, rare >35 years) 1
• Pain duration typically <24 hours at presentation 3
• Absent cremasteric reflex 4
• High-riding testicle 4
• Normal urinalysis does not exclude torsion 1

Epididymitis:

• Gradual onset of pain 1
• Older age (most common in adults >25 years, mean age 40.7 years) 1, 3
• Longer duration of symptoms (average 4.5 days at presentation) 3
• May have abnormal urinalysis, though normal urinalysis does not exclude epididymitis 1

Definitive Diagnostic Approach

When testicular torsion cannot be clinically excluded, immediate Duplex Doppler ultrasound is indicated, but high clinical suspicion should never delay surgical exploration 1:

• Ultrasound sensitivity ranges from 69-96.8% with specificity 87-100%, meaning false negatives occur in up to 30% of cases 1, 3
• The "whirlpool sign" of twisted spermatic cord has 96% sensitivity and is the most specific finding 1, 4
• Decreased or absent testicular blood flow on color Doppler is the key finding 1
• Power Doppler is particularly useful in prepubertal boys with normally reduced flow 1

Critical Time-Sensitive Management

Surgical exploration must occur within 6-8 hours of symptom onset to prevent permanent testicular loss 1, 5:

• Testicular salvage rate is 81.8% when treated promptly 3
• Any patient <16 years with pain duration <24 hours requires urgent evaluation to exclude torsion 3
• Immediate urological consultation is mandatory when torsion is suspected, regardless of imaging results if clinical suspicion remains high 1

Clinical Bottom Line

Do not use Prehn sign to differentiate testicular torsion from epididymitis—it is unreliable and potentially dangerous. Instead, rely on age, onset pattern, pain duration, and urgent Doppler ultrasound, while maintaining a low threshold for surgical exploration in any patient where torsion cannot be definitively excluded 1, 2.