DIAGNOSTIC ACCURACY OF ULTRASOUND IN DETECTING URETERIC STONES USING NON-ENHANCED COMPUTED TOMOGRAPHY AS THE GOLD STANDARD

Abstract

Background: Ureteric stones are a common urological emergency. While non-enhanced computed tomography (CT) is the gold standard, its use is limited by ionizing radiation, cost, and availability. Ultrasound presents a safer, more accessible alternative, though its diagnostic accuracy, particularly in local settings, requires further validation.

Objective: To determine the diagnostic accuracy of ultrasound in detecting ureteric stones in adults, using non-enhanced CT as the gold standard.

Methods: This cross-sectional validation study was conducted at the Radiology Department of Combined Military Hospital Abbottabad over six months. A total of 207 consecutive patients presenting with symptoms suggestive of ureteric colic were enrolled. All participants underwent both ultrasonography (using a color Doppler machine) and non-enhanced CT (using a 64-slice scanner). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall accuracy of ultrasound were calculated against CT findings.

Results: Out of 207 patients, 205 were confirmed to have ureteric stones on CT. Ultrasound correctly identified 185 of these as positive (true positives) but missed 20 (false negatives). Ultrasound correctly ruled out the disease in 2 patients (true negatives) but gave a false positive result for 0 patients. The calculated sensitivity of ultrasound was 90.2%, specificity was 100%, PPV was 100%, NPV was 9.1%, and overall diagnostic accuracy was 90.3%.

Conclusion: Ultrasound demonstrates high specificity and positive predictive value for diagnosing ureteric stones. However, its relatively lower sensitivity and notably low negative predictive value mean a negative ultrasound scan cannot reliably rule out a ureteric stone. Therefore, in cases of high clinical suspicion with a negative ultrasound, CT remains an essential diagnostic tool.