The most common cause of Renal scarring in a 3 year old child is
vesicoureteral reflux (VUR) has been considered the most impoant risk factor for post-UTI renal scar formation in children. VUR predisposes children with UTI to pyelonephritis, and both are associated with renal scarring. Reference: GHAI Essential pediatrics, 8th edition
Trauma
Tuberculosis
Vesicoureteral reflux induced pyelonephritis
Interstitial nephritis
Urinary tract