Several studies show that omega-3 alleviated oxidative stress and inflammation.This study is a simple randomized clinical trial (RCT) evaluating the effect of omega-3 in addition to antibiotic on preventing renal scaring after acute pyelonephritis in children. This randomized clinical trial on 60 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 with neurogenic bladder, systemic hypertension, obstructive uropathy and high grade vesicouretera are excluded.Patients in Intervention group are administered omega-3 based on body weight in divided doses in addition to antibiotic regimens and patients in control group received antibiotic regimens without omega-3. Primary outcome is the development of renal scar by doing DMSA renal scan on the 7th day of admission and four to six months after the intervention and compared between groups.Also,measurement of urinary biomarker of acute kidney injury (NGAL) three days after antibiotic or omega-3 administration for assessing of subsequent scarring in both groups will be done . Secondary outcome is the incidence and severity of renal scarring after pyelonephritis and response to treatment between two groups.