Which imaging modality is often first-line for suspected nephrolithiasis in adults?

• A. Non-contrast CT abdomen/pelvis
• B. Ultrasound kidney
• C. MRI abdomen
• D. Plain abdominal X-ray

Answer: (A)

Non-contrast CT of the abdomen and pelvis is the preferred first-line imaging for suspected nephrolithiasis in adults because it quickly and accurately detects stones of all types and locations without the need for contrast. It also shows the size and exact location of the stone and reveals any resulting obstruction through hydronephrosis, helping to guide urgent management decisions. In addition, CT can identify alternative causes of flank pain that might mimic stones, all in one test.

Ultrasound, while safer regarding radiation and useful in pregnancy or when minimizing radiation is essential, is less reliable for detecting small or distal ureteral stones. MRI is not typically used for stone detection due to poor sensitivity for calcifications. Plain abdominal X-ray misses many stones (especially radiolucent ones) and cannot reliably assess obstruction or provide comprehensive anatomical information.