The actual surgical and medical management of post-natal urinary tract obstruction due to UPJ is a controversial entity. Safe effective interventions have been developed, but controversy arises regarding the necessity and timing of surgical intervention. Much of this debate stems from the inability of sonography and renography to accurately assess the degree of obstruction and renal function. Generally, about 25% of children who present with diminished function or poor kidney drainage will ultimately require a surgical intervention. Different approaches to management range from aggressive observation with serial studies to repair of any obstruction when delayed drainage is seen on nuclear studies.