Predictive values of haematuria and hydronephrosis in suspected renal colic: An emergency department retrospective audit

OBJECTIVE: To determine the predictive values of haematuria and hydronephrosis in suspected renal colic. METHODS: We undertook a retrospective audit of adult patients who received a computed tomography (CT) of the kidneys, ureter and bladder (CTKUB) for suspected renal colic, presenting to Eastern Health Emergency Departments in Melbourne, Australia, between 1 January 2016 and 30 June 2016. CT hydronephrosis was used as a substitute for ultrasound hydronephrosis. We looked at the association of haematuria and CT proven hydronephrosis with CT proven ureteric and obstructing pelvic calculi. RESULTS: Of 769 adult cases who received a CTKUB for suspected renal colic, 384 were positive (49.9%) and 385 were negative (50.1%). For haematuria and renal colic, sensitivity was 87.3% (83.3-90.7), specificity 33.8% (28.9-39.0), positive predictive value (PPV) 55.7% (53.7-57.8), negative predictive value (NPV) 73.6% (67.1-79.3). For CT hydronephrosis and renal colic, sensitivity was 88.0% (84.2-91.1), specificity 85.0% (80.9-88.5), PPV 85.7% (82.4-88.5), NPV 87.4% (84.0-90.2). Of 110 cases with both negative CT hydronephrosis and negative haematuria, four had ureteric calculi, NPV 96.4% (90.8-98.6). CONCLUSION: This audit suggests that a diagnostic strategy relying on the absence of haematuria or hydronephrosis, or both, to rule out ureteric calculi may result in a small number of stones being missed.