Purposes of this study will be as follows:

1. To design a prospective, randomized, and open-labeled study to investigate the effect and the side effect of MPD in combination with conventional antibiotics to affect clinical course, outcome, and medical expenses.
2. To compare level of the urinary and serum cytokines before and after received MPD for the following sub-aim:

I. To determine the population who is benefit from MPD to reduce the severity of clinical course and subsequent renal scarring.

II. To understand the mechanism by which the MPD could shorten the clinical course and reduce the renal scarring.

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:

1. To design a prospective, randomized, and open-labeled study to investigate the effect and the side effect of MPD in combination with conventional antibiotics to affect clinical course, outcome, and medical expenses.
2. To compare level of the urinary and serum cytokines before and after received MPD for the following sub-aim:

I. To determine the population who is benefit from MPD to reduce the severity of clinical course and subsequent renal scarring.

II. To understand the mechanism by which the MPD could shorten the clinical course and reduce the renal scarring.

According to these studies, we will provide a new and effective guideline to shorten disease course, save medical expenses, and decrease the risk for renal scarring sequela.

Inclusion Criteria:

• 1week old ~ 16 years old children with UTI

Exclusion Criteria:

• Previous UTI
• Known GU tract obstruction
• Severe sepsis with vital signs change
• Antibiotics used