Antenatal Hydronephrosis

Antenatal hydronephrosis (AHN), also called urinary tract dilation, has been increasingly recognized with the widespread use of fetal ultrasound. Pediatricians, neonatologists, pediatric surgeons, and/or pediatric urologists are often faced with newborns and/or infants with asymptomatic hydronephrosis (HN) detected in utero and are expected to make management decisions regarding their ultrasonographic findings. In most instances, mild to moderate HN carries no clinical relevance as it resolves spontaneously after birth. However, there is a group of infants with urinary tract dilation who merit investigation and should be managed accordingly in order to avoid complications such as urinary tract infections and/or loss of renal function. In this chapter, we will discuss the main urological malformations associated with AHN, as well as their postnatal evaluation and management.