What is the differential diagnosis for unilateral testicle pain in an adolescent?

Differential Diagnosis for Unilateral Testicular Pain in Adolescents

The three most common causes of acute unilateral testicular pain in adolescents are testicular torsion (a surgical emergency), epididymitis/epididymo-orchitis, and torsion of the testicular appendage, which together account for 85-90% of cases. 1

Primary Differential Diagnoses

1. Testicular Torsion (Surgical Emergency)

• This is the most critical diagnosis to exclude, as testicular viability is compromised if not treated within 6-8 hours of symptom onset. 2
• Testicular torsion has a bimodal age distribution with peaks in neonates and postpubertal boys, making adolescents a high-risk population. 2
• Classic presentation includes sudden onset of severe unilateral scrotal pain, often with nausea and vomiting. 2
• Physical examination typically reveals a negative Prehn sign (pain is NOT relieved when the testicle is elevated), absent cremasteric reflex, and a high-riding testicle. 2
• Important caveat: Testicular torsion can present with minimal or absent severe pain in some cases, which can lead to delayed diagnosis. 3 This atypical presentation should not exclude torsion from the differential.

2. Epididymitis/Epididymo-orchitis

• Most common cause of testicular pain in adults over 25 years, but can occur in adolescents, particularly those who are sexually active. 2
• Characterized by more gradual onset of pain compared to torsion. 2
• Physical examination shows a positive Prehn sign (pain IS relieved with testicular elevation). 1
• Doppler ultrasound demonstrates increased blood flow to the affected testicle, contrasting with the decreased/absent flow seen in torsion. 1
• Consider urinalysis to evaluate for urethritis or urinary tract infection. 2

3. Torsion of Testicular Appendage

• Most common cause of testicular pain in prepubertal boys, but can occur in adolescents. 2, 1
• The pathognomonic "blue dot sign" (visible through scrotal skin) is only present in 21% of cases. 2
• Generally less severe presentation than testicular torsion. 1
• Doppler ultrasound shows normal testicular blood flow, helping differentiate from testicular torsion. 2

Diagnostic Approach Algorithm

Immediate Clinical Assessment

• Determine timing and onset of pain: abrupt onset suggests torsion, while gradual onset suggests epididymitis. 2
• Assess for nausea/vomiting (common with torsion). 2
• Perform physical examination for Prehn sign, cremasteric reflex, and testicular position. 2
• If clinical suspicion for torsion is high based on sudden severe pain and physical findings, proceed directly to immediate urological consultation and surgical exploration without imaging. 2, 4

For Intermediate Clinical Suspicion

• Urgent Duplex Doppler ultrasound of the scrotum is recommended, which should include: 2
  • Grayscale examination to assess testicular homogeneity and identify the "whirlpool sign" of twisted spermatic cord (96% sensitivity). 2
  • Color Doppler assessment of testicular perfusion (96-100% sensitivity for torsion, showing decreased or absent blood flow). 2
  • Power Doppler evaluation. 2
  • Use the contralateral asymptomatic testicle as an internal control. 2

Critical Pitfalls to Avoid

• False-negative Doppler evaluations can occur with partial torsion or spontaneous detorsion. 2 If clinical suspicion remains high despite normal ultrasound, proceed with surgical exploration.
• Do not delay surgical exploration to obtain imaging if clinical presentation strongly suggests torsion. 4 The 6-8 hour window is critical for testicular salvage.
• Bilateral testicular examination is essential, as bilateral torsion, though rare, can occur. 5
• Emergency testing for torsion is indicated when pain onset is sudden, pain is severe, and test results do not support urethritis or urinary tract infection. 2

Less Common Causes to Consider

• Strangulated inguinal hernia. 6
• Traumatic hematoma (if trauma history present). 6
• Testicular tumor. 6
• Testicular fracture (if trauma history present). 6

Management Based on Diagnosis

• Testicular torsion: Immediate urological consultation and prompt surgical exploration with detorsion within 6-8 hours. 2 Surgical outcomes are better when surgery occurs within 12 hours of symptom onset. 2
• Epididymitis: Antibiotics, bed rest, scrotal elevation, and analgesics. 2
• Torsion of testicular appendage: Conservative management with analgesics and observation in most cases. 1