A 35-year-old male presents to the emergency department with sudden onset severe right flank pain radiating to the groin, associated with nausea and hematuria. Suspecting nephrolithiasis, which imaging modality is the most appropriate initial choice?

Explanation

Non-contrast CT KUB (Kidneys, Ureters, Bladder) is the imaging modality of choice for suspected nephrolithiasis. It has high sensitivity and specificity for detecting stones of all compositions (including radiolucent stones), determining their size and location, and identifying complications like hydronephrosis. While renal ultrasound can detect hydronephrosis and larger stones, it is less sensitive for ureteral stones and smaller stones. KUB X-ray only detects radiopaque stones and has low sensitivity. Intravenous pyelogram (IVP) is an older, more invasive technique with radiation and contrast risks, largely replaced by CT for this indication.