Background: Erythrocyte sedimentation rate (ESR), serum C-reactive protein (CRP), urinary β2 microglobulin, antibody-coated bacteria in the urine sediment, and urinary lactic dehydrogenase (LDH) are more traditional tests used to diagnose true pyelonephritis. Acute-phase dimercaptosuccinic acid (DMSA) scan is a sensitive method for diagnosis of true pyelonephritis. Objectives:Defining predictive values of traditional inflammatory serologic parameters, urine analysis indexes, kidney ultrasonography and fever in children with febrile urinary tract infection for predicting renal cortical involvement. Patients and Methods:In a prospective study, 20 children admitted due to febrile urinary tract infection were assessed for renal cortical involvement by Technetium-99 m-labeled dimercapto succinic acid (TC99-DMSA) scan. Body temperature ≥ 39C, white blood cell count ≥ 15000 cell/µL, positive C-reactive protein, erythrocyte sedimentation rate (first hour) ≥ 30 mm/h, presence of proteinuria, severe pyuria or bacteriuria on urine analysis, urine specific gravity ≤ 1010, and renal ultrasonography were used for predicting renal cortical involvement. Sensitivity, specificity, positive and negative predictive values of these variables were measured by specific formula. Results:The highest measured sensitivity was 100% (erythrocyte sedimentation rate ≥ 30 mm/h). Urine specific gravity < 1010 and bacteriuria had the highest (75%) and lowest (20%) specificities respectively. The highest and lowest positive predictive values were 85.7% ( urine specific gravity < 1010) and 57% (proteinuria), whereas the highest and lowest negative predictive values were related to erythrocyte sedimentation rate > 30 mm/h (100%) and proteinuria (11%) respectively. Normal sonography had a low sensitivity for predicting absence of renal involvement (23%). Conclusions:Erythrocyte sedimentation rate ≥ 30 mm/h is a sensitive marker with high negative predictive value for predicting renal involvement in febrile urinary tract infection.