Validation of emergency physician ultrasound in diagnosing hydronephrosis in ureteric colic

Patients presenting to the ED with obstructive nephropathies benefit from early detection of hydronephrosis. Out of hours radiological imaging is expensive and disruptive to arrange. Emergency physician ultrasound (EPU) could allow rapid diagnosis and disposition. If accurate it might avert the need for formal radiological imaging, exclude an obstruction and improve patient flow through the ED.

This was a prospective study of a convenience sample of all adult non-pregnant patients with presumed ureteric colic attending the ED with prior ethics committee approval. An emergency physician or registrar performed a focused ultrasound scan and were blinded to the patient's other management. A computerized tomography scan was also performed for all patients while in the ED or within 24 h of the EPU. The accuracy of EPU detection of hydronephrosis was determined; using computerized tomography scans reported by a senior radiologist as the 'gold-standard'.

Sixty-three patients with suspected ureteric colic were enrolled of whom 57 completed both EPU and computerized tomography imaging. Forty-nine had confirmed nephrolithiasis by computerized tomography with 39 having evidence of hydronephrosis. Overall prevalence of hydronephrosis was 68% (95% confidence interval [CI] 56-79%); compared with computerized tomography, EPU had a sensitivity of 80% (95% CI 65-89%); specificity of 83% (95% CI 61-94%); positive predictive value of 91% (95% CI 75-98%) and negative predictive value of 65% (95% CI 43-83%). The overall accuracy was 81% (95% CI 69-89%).

Although the accuracy of detection of hydronephrosis after focused training in EPU is encouraging, further experience and training might improve the accuracy of EPU and allow its use as a screening tool.