BACKGROUND: Hydronephrosis is commonly detected during antenatal ultrasound (US) scans. Conflicting data exist concerning optimal timing for initial postnatal US and in scheduling follow up. OBJECTIVE: The aim of this work was to define the role of postnatal US in cases of antenatal hydronephrosis, and to settle a protocol for follow up. METHODS: This was a cross section observation study. We studied 212 patients (424 kidneys) with antenatal hydronephrosis. Abdominal ultrasound and color

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... nd and color Doppler was performed. The greatest anterior-posterior diameter of the renal pelvis was measured in the transverse plan. Data analysis was performed using SPSS 17.0 Differences in clinical characteristics were tested by chi-square test. A p value <0.05 was considered statistically significant. RESULTS: 81.2% of kidneys were normal while 18.8% had hydronephrosis. Hydronephrosis was mild in 68.8%, moderate in 19.5% and severe in 11.7%, unilateral in 34.4% and bilateral in 65.6%, left sided more than right sided with the male to female ratio = 2:1 First US follow up showed improvement in 42.2%. Second US follow up was normal in 54.4% .Only 26 renal unites presented for third follow up. CONCLUSION: Investigation of mild/moderate hydronephrosis is better delayed 5-10 days until good urine flow is established.Severe hydronephrosis requires immediate imaging and further investigations. In neonates with prenatal dilatation and postnatal normal renal pelvis, one control scan during the fourth week of life is enough.All remaining uncomplicated hydronephrosis can be serially monitored with ultrasonography at 6 then 12 monthly intervals until resolution is documented. ABSTRACT to 1.4% of fetuses. 5 However, HN does not necessarily translate into obstruction. Moreover, many cases of neonatal HN improve or resolve spontaneously without surgical intervention. 4