Abstract：OBJECTIVE: To explore the relationship of pyelic separation with gestational age, body weight and sex in early newborns. METHODS: A total of 320 neonates were examined by renal ultrasound 2-7 days after birth. The neonates included 180 boys and 140 girls, with a mean gestational age of 36±3 weeks (28-42 weeks) and a mean birth weight of 2430±1000 g (900-4870 g). Correlation analysis was performed between renal pelvis anteroposterior diameter (APD) and gestational age/body weight. The newborns were grouped based on gestational age, body weight and sex and the incidence of pyelic separation was compared among the groups. RESULTS: Pyelic separation was found in 100 of the 320 newborns. The incidence of pyelic separation in boys (37.8%, 70 cases) was significantly higher than in girls (22.2%, 30 cases) (P0.05). There significant difference in the incidence of pyelic separation between different gestational age groups (P>0.05). APD was positively correlated with gestational age and birth weight (P<0.05). The incidence of pyelic separation was negatively correlated with birth weight in all newborns except those who were macrosomic (P<0.05). CONCLUSIONS: The incidence of pyelic separation in early newborns is closely associated with birth weight and sex. APD is positively correlated to gestational age and birth weight. Pyelic separation often occurs more frequently on the left side or both sides than on the right side.
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