Introduction: The timely diagnosis and treatment of testicular torsion is essential as a longer duration of symptoms is correlated with testicular necrosis and infertility. Ultrasound imaging assists in separating this diagnosis from other causes of acute scrotal pain. Our objective was to characterize which ultrasound findings predicted surgical intervention. Methods: We performed a retrospective health records review of all patients, ages 0-17 years that presented to the emergency department of the Children’s Hospital of Eastern Ontario over a 5-year period (2009-14) with scrotal pain <24 hours duration who were assessed by an emergency physician (EP) and received a testicular ultrasound by the Diagnostic Imaging Department. Patients’ records and ultrasound reports were reviewed by two reviewers who recorded ultrasound findings, times of EP assessment, ultrasound and surgical intervention in a standardized data extraction form. Sensitivity, specificity and positive and negative predictive values were calculated for the ultrasound findings. Results: 190 patients were analyzed of which 34 had a final diagnosis of testicular torsion (mean age 11.5 years, range 0-17.3). The mean time from EP assessment to ultrasound was 67.6 minutes (95%CI 50.5-84.6) during the daytime (800-2159) and 83.2 minutes (95%CI 36.7-130.4) for overnight presentations (2200-759). The absence of blood flow on colour Doppler ultrasound of the affected testicle was the best predictor of surgical intervention (sensitivity=94.1% [95%CI 80.3%-99.3%], specificity=99.4% [95%CI 96.5%-99.9%], positive likelihood ratio=146.8 [95%CI 20.7-1037.7] and negative likelihood ratio=0.06 [95%CI 0.02-0.23]. Other ultrasound findings that help rule in testicular torsion were the presence of a heterogeneous testicle on the symptomatic side (specificity=91.0% [95%CI 85.4%-95.0%] and the presence of the whirlpool sign (specificity=99.4% [95%CI 96.5%-99.9%]). Conclusion: The absence of blood flow on ultrasound is the best ultrasound finding for predicting surgical management of testicular torsion. Neither a heterogeneous testicle nor whirlpool sign had strong enough sensitivity to warrant their independent use. Future studies, such as those utilizing point of care ultrasound by EPs, should be conducted to study the affect on delays in treatment.