Predicting the need for radiologic imaging in adults with febrile urinary tract infection.

Background: Radiologic evaluation of adults with febrile urinary tract infection (UTI) is frequently performed to exclude urological disorders. This study aims to develop a clinical rule predicting need for radiologic imaging.
Methods: We conducted a prospective, observational study including consecutive adults with febrile UTI at 8 emergency departments (EDs) in the Netherlands. Outcomes of ultrasounds and computed tomographs of the urinary tract were classified as "urgent urological disorder" (pyonephrosis or abscess), "nonurgent urologic disorder," "normal," and "incidental nonurological findings." Urgent and nonurgent urologic disorders were classified as "clinically relevant radiologic findings." The data of 5 EDs were used as the derivation cohort, and 3 EDs served as the validation cohort.
Results: Three hundred forty-six patients were included in the derivation cohort. Radiologic imaging was performed for 245 patients (71%). A prediction rule was derived, being the presence of a history of urolithiasis, a urine pH ≥7.0, and/or renal insufficiency (estimated glomerular filtration rate, ≤40 mL/min/1.73 m(3)). This rule predicts clinically relevant radiologic findings with a negative predictive value (NPV) of 93% and positive predictive value (PPV) of 24% and urgent urological disorders with an NPV of 99% and a PPV of 10%. In the validation cohort (n = 131), the NPV and PPV for clinically relevant radiologic findings were 89% and 20%, respectively; for urgent urological disorders, the values were 100% and 11%, respectively. Potential reduction of radiologic imaging by implementing the prediction rule was 40%.
Conclusions: Radiologic imaging can selectively be applied in adults with febrile UTI without loss of clinically relevant information by using a simple clinical prediction rule.