Background: Renal ultrasound (RUS) is frequently used as part of the routine work-up for acute kidney injury (AKI) for the hospitalized patient.  Society guidelines and previous literature suggest that RUS should be ordered when an obstructive cause of AKI is suspected.  While RUS is a non-invasive, low-cost imaging modality that does not expose patients to radiation, overutilization may lead to increased healthcare costs, and it often identifies incidental abnormal findings with minimal clinical relevance. At another institution, a risk stratification was devised that found that a large portion of ultrasounds were low-yield in identifying hydronephrosis or obstruction (Licurse et al., 2010). We hypothesized that if our data were similar, we could identify an approach to use RUS more appropriately.

Methods: We retrospectively reviewed 281 charts of patients who (1) were admitted to the hospitalist service (2) experienced AKI (Cr rise > 0.3 or greater than 50%) and (3) had an RUS ordered from 6/9/2013 and 10/24/2014 at Mount Sinai Hospital (MSH). We performed a detailed chart review using the seven criteria from Licurse et al. to stratify each patient’s risk for hydronephrosis: history of hydronephrosis; recurrent urinary tract infections; diagnosis consistent with obstruction; nonblack race; and absence of the following: exposure to nephrotoxic medications, congestive heart failure, or prerenal AKI.

Results: 111 patients were deemed high risk for hydronephrosis. 30 of these patients (27%) were found to have hydronephrosis. 170 patients were deemed to have medium or low risk for hydronephrosis. 5 of these patients (3%) were found to have hydronephrosis.

Conclusions: Our study validates Licurse et al.’s approach to risk-stratifying patients at risk of hydronephrosis. Five of the seven factors identified were independently significantly predictive of hydronephrosis in the MSH patient population. In this sample, 60% of patients were not at high risk for hydronephrosis with very low incidence of hydronephrosis in that group. This finding presents an opportunity to optimize utilization of this imaging modality by reducing resources and patient harm from incidental findings. We plan to integrate this risk stratification in clinician education and decision-support tools for work-up of AKI at MSH.