Rate and yield of imaging for acute pyelonephritis in the emergency department: A retrospective cohort study

The role of imaging in acute pyelonephritis (APN) in the ED is poorly understood, with variability among clinical guidelines for when patients should be imaged, and the modality of imaging. The objective of this study was to identify the proportion of patients with APN being imaged, the proportion abnormal findings, and the association between abnormal imaging and discharge disposition.

A single-centre retrospective review of patients with a discharge diagnosis of APN at an adult tertiary referral hospital over a 5-year period (2018-2022) was conducted. The proportion of patients with APN investigated with imaging, and abnormalities on imaging were reported. Logistic regression analyses were performed to assess whether imaging was associated with change in disposition from the ED.

There were 778 patients included for analysis. Among these, 210 (27%) were investigated with ultrasound (US) and/or computed tomography (CT) in the ED. Of the 214 imaging reports available, 112 (52%) were abnormal. Imaging was associated with hospital ward admission (adjusted odds ratio [aOR] 5.28; 95% confidence interval [CI] 3.35-8.31) as was abnormal imaging (aOR 4.51; 95% CI 2.62-7.75). Other variables associated with hospital ward admission were higher temperature and heart rate, higher C-reactive protein levels and poorer renal function.

Among patients with APN, abnormalities on imaging were common and both imaging and abnormalities on imaging were associated with hospital ward admission. This suggests that there is possible utility of early and routine imaging for patients with APN to allow clinicians to efficiently make decisions about patient disposition.