Text Box: THE CHARACTERISTIC OF MICTURITION AND CHANGE OF PLASMA URINE OSMOLARITY IN NEONATES Wu B-Q, Xu W-R, ZH-Q Department of Pediatrics, Second Affiliated Hospital, Jinan Medical College, Jinan University, Shenzhen, China Objective: To assess the micturition characteristic, bladder capacity and plasma urine osmolarity in neonates Methods: 45 newborns were divided into A, B and C groups according to day-age that were ~3d, ~7d and >7d respectively. The time of micturition and voided volume were recorded .The residual urine volume was detected by bladder volume instrument (Bladder Scan BVI-2500). The plasma and urine osmolarity were measured by FM-6 pattern freezing point osmometer. Results: (1) There was significantly difference (P<0.05) of daynight voided volume、voided frequency between A group and those of B,C groups. (2) Bladder emptying rate , maxium bladder capacity (MBC) and plasma urine osmolarity of A, B and C groups were 80±0.07, 0.82 ±0.09, 0.79±0.10; 56±6, 65±14, 61±15 (ml)；285±5, 287±7, 286±8 (mOsm/L)；202±59, 185±65, 216±92 (mOsm/L) respectively and there were no significantly difference among three groups. ⑶ Used the multiple stepwise regression methods to estabilish the best regression equation for predicting the MBC, MBC = 42+0.17*X (ml), X= eight hours (10Am~ 6Pm) voided volume, F=15.561 (P<0.001). Conclusions: The normal newborn’s bladder was stable and emptied almost completely. There is no difference for the renal concentration function of neonate between day and night. 1041