It has previously been found that there is no correlation between degree of hydronephrosis and presence of reflux; however this is oftentimes the criteria physicians use to obtain a VCUG.

Investigators conducted a previous retrospective study to evaluate other possible findings on ultrasound that may better predict reflux. Investigators found that if a postnatal ultrasound showed any of the three findings of hydroureter, duplication or dysmorphic kidney, then the odds ratio of detecting reflux was 8.07 (95%CI 3.86, 16.87). The purpose of this study is to perform a randomized prospective study to validate this retrospective study. Investigators hypothesis is that patients with hydronephrosis alone will be more likely to have negative VCUG studies; hence obtaining a VCUG for this indication may not be warranted.

Inclusion Criteria:

• Patients with a history of antenatal hydronephrosis who have a post-natal ultrasound demonstrating hydronephrosis alone and no other abnormalities

Exclusion Criteria:

• Patients with a post-natal ultrasound demonstrating bilateral hydronephrosis
• Patients with a history of posterior urethral valve or when a valve is suspected
• Patients who have hydronephrosis on ultrasound as well as other findings including duplication, hydroureter, dysmorphic kidneys, or bladder abnormalities