Risk factors for parenchymal damage in urinary tract infection are vesicoureteral reflux (VUR),obstructive uropathy,the number of flares of acute pyelonephritis(APN) and delay in treatment of acute infection.The pathogenesis of APN is related to bacterial virulenece,immune response,tissue factors,apoptosis and production of free radicals that lead to fibrosis and renal scarring. Oxidative stress in renal cells may be a critical factor in the pathogenesis of pyelonephritis whereas pharmacological management of the oxidative stress response may provide a therapeutic effect in preventing renal pathologies. Animal model show that L-carnitine alleviated oxidative stress, and acute renal inflammatory injury can be prevented much more effectively by carnitine in addition to conventional antibiotic treatment in pyelonephritis.This study is a simple randomized clinical trial (RCT) evaluating the effect of L-carnitine in addition to antibiotic on preventing renal scaring after acute pyelonephritis in children. Simple non- blind randomized clinical trial on 78 patients in 2 groups (intervention & control) is conducted.Children aged 1 month to 10 years with positive urine culture, clinical findings, and 99mTc-dimercaptosuccinic acid (DMSA) scintigraphy-based evidence in favor of acute pyelonephritis were enrolled into a clinical trial. Patients were excluded if they had neurogenic bladder, systemic hypertension, obstructive uropathy. Patients in Intervention group are administered 50 mg/kg/day carnitine in divided 2-3 times/day (maximum 3 g/day) in addition to antibiotic regimens and patients in control group received antibiotic regimens. Primary outcome is the development of renal scar by doing DMSA renal scan on the 7th day of admission and six months after the intervention and compared between groups and secondary outcome is the incidence and severity of pyelonephritis and response to treatment.