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Renal ultrasound accurately identifies hydronephrosis but it is less sensitive than computerized tomography for the detection of ureterolithiasis. We investigated whether the presence of hydronephrosis on ultrasound was associated with a ureteral stone in patients who underwent both ultrasound and computerized tomography during the evaluation of acute renal colic.We retrospectively reviewed the records of patients from 3 institutions who were evaluated for acute renal colic by both ultrasound and computerized tomography between 2012 and 2015. Patients were included in analysis if ultrasound and computerized tomography were performed on the same day. The presence of ureterolithiasis, stone location and hydronephrosis was reviewed and compared between imaging modalities.Ureteral stones were present in 85 of 144 patients. Ultrasound identified hydronephrosis in 89.8% of patients and a ureteral stone in 25.9%. Computerized tomography identified hydronephrosis in 91.8% of patients and a ureteral stone in 98.8%. In 75.0% of cases the presence or absence of hydronephrosis on ultrasound correctly predicted the presence or absence of a ureteral stone on computerized tomography. Hydronephrosis on ultrasound had a positive predictive value of 0.77 for the presence of a ureteral stone and a negative predictive value of 0.71 for the absence of a ureteral stone.Hydronephrosis on ultrasound did not accurately predict the presence or absence of a ureteral stone on computerized tomography in 25.0% of the patients in this study. Ultrasound is an important tool for evaluating hydronephrosis associated with renal colic but patients may benefit from other studies to confirm the presence or absence of ureteral stones.