Risk stratification

Our primary predictor was high-risk, medium-risk, or low-risk category for hydronephrosis based on the risk stratification framework developed by Licurse et al (online supplemental table 1).¹² The following are the seven criteria included in the framework: a history of hydronephrosis (4 points), and non-black race, history of recurrent urinary tract infections (UTIs), diagnosis consistent with possible obstruction (abdominal or pelvic mass, benign prostatic hypertrophy, pelvic surgery, or neurogenic bladder), absence of exposure to inpatient nephrotoxic agents (aspirin >81 mg, diuretics, ACE inhibitors or vancomycin), absence of congestive heart failure, and/or absence of prerenal AKI (pressor use or sepsis) (1 point each). A total score of 4 or more points was classified as high risk, 3 points as medium risk, and 2 or fewer points as low risk.¹² We performed an additional sensitivity analysis defining prerenal AKI as pressor use, sepsis or history of hypotension, defined as at least two consecutive blood pressure measurements below 80 mm Hg systolic or below 60 mm Hg diastolic. Additional predictors were presence of nephrology consultation and RUS recommended by nephrology.

bmjopen-2020-046761supp001.pdf

We performed a retrospective chart review of data in the electronic health record (EHR) to determine the presence or absence of each predictor, using only data available before the RUS was ordered. One author (JZ) performed the initial chart review, which was recorded in the REDCap web-based application (Vanderbilt University). Another author (CG) independently reviewed a random selection of 10% of medical records, with 96% agreement (Cohen’s κ=0.913, p<0.001).