Testicular torsion is characterized by the sudden onset of testicular pain associated with abdominal pain, nausea and vomiting. Fever is unusual and urinalysis is often normal. Fever, pyuria, dysuria and urethral discharge are characteristic of epididymitis. Radionuclide scanning and Doppler ultrasound are helpful in establishing the diagnosis. If the diagnosis is uncertain, the patient should be considered to have testicular torsion until it is proved otherwise. Undiagnosed torsion leads to testicular necrosis.