What is the most likely diagnosis for a boy presenting with sudden onset testicular pain and swelling, absent cremasteric reflex, and negative transillumination test?

Testicular Torsion

The most likely diagnosis is A. Testicular torsion, and this patient requires immediate urological consultation and surgical exploration within 6-8 hours of symptom onset to prevent permanent testicular loss. 1

Clinical Reasoning

This presentation is classic for testicular torsion based on several key diagnostic features:

Pathognomonic Clinical Findings

• Sudden onset of severe testicular pain in a boy is the hallmark presentation of testicular torsion, distinguishing it from epididymitis which has gradual pain onset 1, 2

• Absent cremasteric reflex is the most accurate clinical sign of testicular torsion and strongly supports this diagnosis 3, 4

• Negative transillumination test excludes hydrocele (option B), which would show light transmission through clear fluid 1

• No fever or trauma history makes epididymitis (option C) less likely, as epididymitis typically presents with more gradual onset and may have systemic symptoms 2, 5

Age-Specific Considerations

• Testicular torsion has a bimodal distribution with peaks in neonates and postpubertal boys, making this age group particularly high-risk 1, 6

• The estimated yearly incidence is 2.9 to 3.8 per 100,000 boys under 18 years 1, 4

Why Other Options Are Incorrect

• Hydrocele (B) would transilluminate positively and presents with painless scrotal swelling, not acute severe pain 1

• Epididymitis (C) typically shows gradual pain onset, positive Prehn sign (pain relief with testicular elevation), and increased blood flow on Doppler ultrasound rather than decreased flow 2, 5

• Varicocele (D) presents as a chronic, painless "bag of worms" sensation in the scrotum, not acute severe pain 1

Critical Time-Sensitive Management

• Surgical exploration must occur within 6-8 hours of symptom onset to prevent permanent ischemic damage and testicular loss 1, 2

• Do not delay surgical consultation for imaging when clinical suspicion is high, as this risks testicular loss 2, 4

• The orchiectomy rate is 42% in boys undergoing surgery for testicular torsion, emphasizing the importance of rapid intervention 4

Common Pitfalls to Avoid

• Do not rely solely on imaging - if clinical suspicion is high based on sudden onset pain and absent cremasteric reflex, proceed directly to surgical exploration 1, 4

• Normal urinalysis does not exclude testicular torsion - this is a common misconception that can delay diagnosis 1

• Doppler ultrasound can give false negatives with partial torsion or spontaneous detorsion, so clinical suspicion should guide management 1, 5