Acute testicular pain requires the clinician to rapidly differentiate testicular torsion (a surgical emergency) from other causes. Testicular torsion occurs when the spermatic cord twists, occluding testicular blood supply -- the 6-hour window for surgical detorsion and orchiopexy is critical for testicular salvage (nearly 100% salvage within 6 hours, decreasing to less than 20% after 12 hours). The bell-clapper deformity (horizontal testicular lie from inadequate fixation of the tunica vaginalis to the scrotal wall) predisposes to torsion. Physical examination reveals a high-riding testis with an abnormal transverse lie, absent cremasteric reflex (sensitivity approximately 99% for torsion when absent), and severe tenderness without relief with testicular elevation (negative Prehn sign, though unreliable). Color Doppler ultrasound confirms absent or decreased intratesticular blood flow. The clinician must differentiate from epididymitis (gradual onset, positive Prehn sign, preserved cremasteric reflex, increased flow on Doppler -- treat with ceftriaxone plus doxycycline if STI-related, or fluoroquinolone if enteric organisms suspected), torsion of the appendix testis (blue dot sign, focal superior pole tenderness, self-limited), and incarcerated inguinal hernia. Any suspected torsion requires immediate urological consultation without delay for...