<qa>  What is the etiology of the febrile children?The urinary tract infection UTI is a common etiology of the febrile children and the acute pyelonephritis APN happen in 70 children with the first febrile UTI. After the first APN, the irreversible renal scarring takes place in about 40 patients. The sequela of the renal scarring includes chronic kidney disease, hypertension, the complication during the pregnancy, and even the end stage of renal diseases. Due to the progression of the pathophysiology of the pyelonephritis and the renal scarring in the past years, we understand that the inflammation is one of the important mechanisms. Therefore, there are many animal studies clarifying the role of the anti-inflammation or antioxidant to reduce the renal scarring. In our previous studies, Dr. Chiou Y.Y. and colleagues has provided the evidence that the adjunctive methylprednisolone MPD can decrease the risk of the renal scarring for patients with high risk APN, which was defined as inflammatory volume more than 4.6 mL on technetium-99m-labeled dimercaptosuccinic acid scan or abnormal renal ultrasonography results. Our study is the first human study demonstrating the solution for the renal scarring. However, whether this result can be applied to the whole spectrum of the UTI is still unknown. Purposes of this study will be as follows: 