A 33-year-old male presents to the emergency department with severe pain radiating from his left flank to his groin. The pain is colicky in nature. On exam, the patient appears to be in acute distress. He is tachycardic and diaphoretic and has left costovertebral tenderness. Urinalysis shows greater than 180 RBCs and 3+ blood. What is the best way to make the diagnosis?