Detection and Diagnosis of Ureteral Stones

Direct Stone Visualization

The American College of Radiology states that gray-scale ultrasound demonstrates sensitivity of only up to 61% for ureteral stone detection, with 100% specificity when stones are seen, and this sensitivity is improved only if there are associated signs of obstruction present 1
The overall sensitivity of ultrasound for stone detection ranges from only 24% to 57% compared to noncontrast CT, with decreased sensitivity for smaller stones 1
Ultrasound has nearly 100% sensitivity for large stones (>5 mm) in the kidney, but accuracy for small stones (<3 mm) is poor, and this does not apply to ureteral stones 2

Ultrasound is up to 100% sensitive and 90% specific for diagnosing ureteral obstruction (hydronephrosis, ureterectasis, and perinephric fluid) in patients with acute flank pain 1
Within the first 2 hours of presentation, secondary signs of obstruction are less sensitive because obstruction findings may not have had time to develop 1

For a 7x4mm distal ureteral stone, noncontrast CT remains the reference standard with 97% sensitivity, far superior to ultrasound 3
Stones >6-7mm have lower spontaneous passage rates, making intervention often recommended 4