The exact role of urinary tract infection in the appearance of chronic kidney disease is unclear. Children with congenital malformations of kidney and urinary tract have the higher risk of impairment of renal function. To understand if the use of antibiotic prophylaxis can reduce the risk of urinary tract infection in children with these malformations, this study will randomize children in two groups. Group A will not take antibiotic prophylaxis, Group B will take antibiotic prophylaxis for 2 years. This study will assess if antibiotic prophylaxis reduce the risk of urinary tract infections in these children and if urinary tract infections influence the appearance of renal damage.