Testicular torsion occurs when the spermatic cord twists, cutting off arterial blood supply to the testis. It is a urologic emergency — salvage rates approach 100% within 6 hours of onset but fall sharply beyond that. Doppler ultrasound is the primary imaging modality: absent or markedly reduced blood flow to the affected testis compared to the contralateral side is the key finding. The testis may appear enlarged and heterogeneous. Color, power, and spectral Doppler are all used to evaluate testicular perfusion. Sonographers must recognize this pattern and communicate findings urgently.