Imaging in Acute Pyelonephritis: Utilization, Findings, and Effect on Management

Objectives To determine the frequency, timing, and types of imaging obtained in patients with a discharge diagnosis of acute pyelonephritis, and how often imaging findings affect therapy. Methods This was a retrospective chart review of 1062 adults with a diagnosis of acute pyelonephritis discharged from an urban, safety-net hospital between January 1, 2008 and December 31, 2012. From the 739 patients selected after exclusions, we determined the number and proportion of patients imaged within the first 24 hours of admission, stratified by risk factors for pyelonephritis complications, and the frequency of positive findings leading to invasive interventions. Results Of 739 patients, 468 (63%) were imaged within 24 hours of admission, 262/414 (63%) of whom had risk factors for complications and 206/325 of whom (63%) did not. Among these, studies were positive in 117/468 (25%), 78/262 (30%) in those with risk factors, and 39/206 (19%) of those without risk factors. Of the 117 patients with positive imaging findings within 24 hours of admission, 58 (50%) underwent invasive procedures, 47 (60%) with risk factors and 11 (28%) without. Among all of the patients, interventions were directed at relieving obstructions much more commonly than treating abscess (51 patients vs 8). Conclusions Among this population, imaging is frequently done earlier than recommended. Because the majority of interventions targeted stone disease, ultrasound may be the preferred initial modality rather than contrasted tomography when obtaining imaging early. Current guidelines may need to be revisited.