Diagnostic accuracy of point-of-care ultrasonography for obstructive cause in patients with acute kidney injury: a prospective diagnosis cohort.

The aim of this study was to evaluate the test characteristics of point-of-care ultrasound (POCUS) in the diagnosis of obstructive acute kidney injury (AKI) in patients presenting with AKI to the Emergency Department (ED). This is a prospective diagnostic accuracy study that took place between July 6th, 2021 and July 6th, 2023 in the ED of an academic hospital. Adult patients visiting the ED and presenting with AKI were eligible for inclusion. Exclusion criteria were: pregnancy, dialysis-dependence, and kidney transplant. The index test was urinary tract POCUS (including kidneys and bladder assessment). The reference standard was obstructive origin of AKI using a two expert panel adjudication. One hundred and twenty-nine patients were included, with 22 (17%) obstructive AKI. For the diagnosis of obstructive AKI, POCUS had a sensitivity = 91% (95% CI = [71-99]), a specificity = 88% (95% CI = [80-93]), a PPV = 61% (95% CI = [42-77]), a NPV = 98% (95% CI = [93-100]), a LR +  = 7.58 (95% CI = [4.42-12.67]) and a LR - = 0.1 (95% CI = [0.03-0.36]). Our study suggests that POCUS has good sensitivity and specificity for the diagnosis of an obstructive origin in presenting to the ED with AKI. Given a NPV of 98%, POCUS has great potential as a tool to rule out obstructive AKI, while its PPV of 61% suggests that positive POCUS likely requires confirmation with radiology-performed ultrasound. Trial registration number: NCT06190522.