Diagnostic accuracy of venous system ultrasound for subtypes of acute kidney injury

Background Management of acute kidney injury (AKI) in the ED can be difficult due to uncertainty regarding the aetiology. This study investigated the diagnostic value of venous system ultrasound for determining the aetiological subtypes of AKI in the ED. Methods This multidisciplinary prospective cohort study was conducted in a single academic ED over the course of a year. Adult patients with AKI were evaluated using the venous excess ultrasound (VExUS) score, which is a four-step ultrasound protocol. The protocol begins with the inferior vena cava (IVC) measurement and examines organ flow patterns, including portal, hepatic and renal veins in the presence of dilated IVC. The AKI subtypes (hypovolaemia, cardiorenal, systemic vasodilatation and renal) were adjudicated by nephrologists and emergency physicians, considering data that became available during the hospitalisation. We determined the diagnostic test characteristics of VExUS for identifying each of the four AKI aetiological subtypes. Results 150 patients with AKI were included in the study. Hypovolaemia was the most frequent finally adjudicated cause of AKI (66%), followed by cardiorenal (18%), systemic vasodilatation (8.7%) and renal (7.3%). In diagnosing the cardiorenal subtype, the area under the curve (AUC) for VExUS grade >0 was 0.819, with 77.8% sensitivity and 80.5% specificity, and the AUC for IVC maximum diameter >20.4 mm was 0.865, with 74.1% sensitivity and 86.2% specificity. For the hypovolaemia subtype, the AUC for VExUS grade ≤0 was 0.711, with 83.8% sensitivity and 56.9% specificity, and the AUC for IVC maximum diameter ≤16.8 mm was 0.736, with 73.7% sensitivity and 68.6% specificity. None of the parameters achieved adequate test characteristics for renal and systemic vasodilatation subtypes. Conclusion The VExUS score has good diagnostic accuracy for cardiorenal AKI and fair accuracy for hypovolaemic AKI but cannot identify renal and systemic vasodilatation subtypes. It should not therefore be used in isolation to determine the cause of AKI in the ED. Trial registration number NCT04948710 .