ABSTRACT
Objective:To explore the method of ultrasonography for detecting the fetal umbilical vein diameter, blood flow volume and normalized volume blood flow and establish normal reference ranges with umbilical vein diameter, blood flow volume and normalized blood flow and Z-scores for umbilical vein diameter and blood volume flow.Methods:This was a prospective study on 907 normal fetuses in the Second Xiangya Hospital, Central South University and Women and Children Healthcare Hospital of Zhuzhou from March 2019 to December 2020. The umbilical vein diameter (Duv), umbilical vein blood flow volume (Quv) and normalized volume blood flow (nQ = Quv/estimated fetal weight) of the free loop of umbilical vein (FUV) and fetal intra-abdominal umbilical vein (IUV) were collected. And the mean values and 90% confidence intervals of Duv, Quv and nQ in two segments of umbilical veins at different gestational ages were calculated. Regression analysis of Duv, Quv and nQ were performed with gestational age (GA), and the parameters of umbilical vein in different segments were compared. Finally, with gestational age (GA) as the independent variable, Z-scores of the Duv and Quv were built.Results:The mean values and 90% confidence intervals of Duv, Quv, and nQ in 858 (94.6%) normal fetal umbilical veins were successfully obtained. The Duv, Quv of the FUV and IUV increased as pregnancy progressed. The Quadratic curve of Duv and Linear curve of Quv were of the highest fitnesses, respectively( r=0.951, 0.941, 0.986, 0.982; all P<0.001). While nQ increased with GA followed by a decreased trend, and the Quadratic curve was the highest fitting curve of nQ( r=0.610, 0.611; all P<0.001). Duv-FUV was greater than Duv-IUV( P<0.001), nQ-FUV was bigger than Quv-IUV( P=0.001), and he difference was not statistically significant between Quv-FUV and Quv-IUV( P=0.133). Z-scores models of Duv and Quv were successfully established, and all Z-scores were Gaussian distribution. Conclusions:The normal ranges and Z-scores of umbilical vein parameters are useful to improve the evaluation of placental circulation and provide a strong basis for the monitoring of fetus-related diseases and the evaluation of pregnancy prognosis. The choice of FUV or IUV umbilical vein to evaluate placental circulation may depend on the actual situation in clinical application.
ABSTRACT
BACKGROUND: When it is difficult to insure adequate blood vessels, an expanded polytetrafluoroethylene (e-PTFE) graft has been accepted as an alternative although its long-term patency is not equal to that of an autogenous arteriovenous fistula (AVF) for the purpose of performing hemodialysis. There being no hemodynamic guidelines for creating an autogenous or e-PTFE AVF, we prospectively investigated the difference in blood flows between autogenous and e-PTFE AVFs after internal AVF creation in order to identify an ideal AVF. METHODS: We performed color doppler ultrasonography on 15 patients who experienced AVF creation between December 1997 and December 1998 at the Wallace Memorial Baptist Hospital in Pusan and compared the volume flow per minute, the peak systolic velocity, and the cross-sectional area between an autogenous and an e-PTFE AVF. RESULTS: Eight (8) patients experienced an autogenous vein AVF creation, and seven (7) patients experienced an AVF creation using 4x6 mm graded e-PTFE (Impra(R)). 1. Average volume flow: 1611.87 +/-687.52 mL/min for autogenous AVFs and 1725.28+/-269.06 mL/min for e-PTFE AVFs (p=0.67). 2. Average peak systolic velocity: 128.98+/-52.83 cm/sec for autogenous AVFs and 81.71+/-8.93 cm/sec in e-PTFE AVFs (p=0.04). 3. Average cross-sectional area: 0.23+/-0.10 cm2 for autogenous AVFs and 0.34+/-0.02 cm2 for e-PTFE AVFs (p=0.02). 4. There were no postoperative complications, such as venous hypertension or distal ischemia, except for one puncture-site infection. CONCLUSIONS: There was no significant difference in volume flows between autogenous AVFs and 4x6 mm graded e-PTFE graft AVFs after internal AVF creation. In the e-PTFE graft AVFs, the cross-sectionalarea was greater and the peak systolic velocity was smaller compared with those of autogenous AVFs. These results suggest that, in e-PTFE AVF creation in order to maintain on adequate minute volume flow, it is important to minimized the cross-sectional area of the outflow vessel where the lower compliance of the e-PTFE graft increases outflow resistance. Also, we conclude that choosing the appropriate blood vessels and using a meticulous surgical technique are mandatory in establishing optimal hemodynamics for arteriovenous fistulae.