The prevalence of malformations of the kidneys is quite high compared to other congenital malformations. In a study of the Association for Neonatology of Mecklenburg-West Pomerania examining 37,634 births, a hydronephrotic kidney was diagnosed in 16.7 of 10,000 children. Depending on the type and severity of the congenital malformation it might be difficult to find out when there is a risk for loss of renal function. Unfortunately, in 2010 health politicians (the Gemeinsame Bundesausschuss) voted against routine ultrasound screening for renal abnormalities in newborns despite an increasing number of pre- or postnatally diagnosed dilated kidneys in recent years. Will this lead to a decrease in the diagnosis of hydronephrosis with possible loss of renal function later on? According to Roth et al. the incidence of in utero dilatations of the urinary tract is about 1:100, but only 1:500 children have a clinically relevant problem. This raises the question of which of these young patients need an intervention and which might be monitored expectantly.