Risk stratification framework to improve the utility of renal ultrasound in acute kidney injury

Acute kidney injury (AKI) is common among hospitalised patients and can lead to significant morbidity or mortality if not properly managed. Renal ultrasound (RUS) is often requested in the initial workup of AKI to rule out obstructive uropathy despite pre-renal aetiologies being implicated in most cases, especially in patients without risk factors for obstruction.

Determine the utility of RUS in detecting bilateral hydronephrosis in the context of AKI, and identify risk factors that can be used to stratify patients to better guide patient management.

Adults who underwent RUS for AKI between January 2019 and December 2021 were reviewed. Renal ultrasound studies that identified bilateral hydronephrosis and the patient characteristics associated with these studies were recorded.

Seven hundred and fifty-eight RUS reports were included. Bilateral hydronephrosis was diagnosed in 43 patients (5.7%). Of these 43 patients, 39 (90.7%) had at least one risk factor for urinary tract obstruction. Bilateral hydronephrosis was only diagnosed in 4 (9.3%) patients without any risk factor for obstruction. The risk factors with the highest odds for being diagnosed with bilateral hydronephrosis included a history of previous ureteric stenting or nephrostomy tube insertion (OR 10.37), previous bilateral hydronephrosis (OR 14.56), or multiple risk factors (OR 23.06).

Renal ultrasound has limited utility in the evaluation of AKI in low-risk patients.

These risk factors can be used to assign patients to high- or low-risk categories to better guide management and reduce the number of unnecessary studies performed while still identifying clinically significant disease.