title: Fetal celiac and splenic artery flow velocity and pulsatility index: longitudinal reference ranges and evidence for vasodilation at a low portocaval pressure gradient.
abstract: OBJECTIVE
  To establish longitudinal reference ranges for the fetal celiac and splenic arteries flow velocity and pulsatility index (PI), and to determine their hemodynamic relationship to venous liver perfusion and distribution and to other essential arteries.
  
  
  METHODS
  This was a prospective longitudinal study of 161 low-risk pregnancies. Doppler recordings of the celiac and splenic arteries were made on three to five occasions at 3-5-week intervals to establish reference ranges for blood velocity and PI measurements. Peak systolic velocity in the ductus venosus, a shunt between the umbilical and inferior caval veins, was used to represent the umbilicocaval (i.e. portocaval) pressure gradient, and the left portal vein blood velocity represented the umbilical distribution to the right liver lobe. The correlations between the celiac, splenic and hepatic arteries were determined, and their association with the middle cerebral and umbilical artery PIs (MCA-PI and UA-PI) was assessed.
  
  
  RESULTS
  Longitudinal reference ranges for the fetal celiac and splenic arteries were established based on 510 and 521 observations, respectively, during gestational weeks 21-39. Terms for calculating conditional reference ranges to be used for repeat observations are provided. Celiac and splenic artery PIs were low when portocaval pressure and umbilical supply to the right lobe were low (P < 0.0001). Their peak systolic velocity and PI were correlated (r = 0.7 (95% CI, 0.6-0.8) and r = 0.5 (95% CI, 0.3-0.6), respectively), while the PI of the hepatic artery correlated weakly with those of the celiac and splenic arteries. They were positively associated with the MCA-PI and UA-PI (P < 0.0001).
  
  
  CONCLUSIONS
  We provide longitudinal reference ranges for the fetal celiac and splenic arteries Doppler measurements and show that they are involved in maintaining portal liver perfusion independently from the hepatic artery.
authors.affiliation: Department of Obstetrics and Gynecology, Haukeland University Hospital, Norway. cathrine.ebbing@molmed.uib.no
authors.forename: C
authors.initials: C
authors.lastname: Ebbing
authors.forename: S
authors.initials: S
authors.lastname: Rasmussen
authors.forename: K M
authors.initials: KM
authors.lastname: Godfrey
authors.forename: M A
authors.initials: MA
authors.lastname: Hanson
authors.forename: T
authors.initials: T
authors.lastname: Kiserud
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D002445:Celiac Artery / Q000196:embryology / Q000502:physiology*; D005333:Fetus / Q000098:blood supply*; D005865:Gestational Age; D006801:Humans; D008099:Liver / Q000098:blood supply* / Q000196:embryology; D015588:Observer Variation; D011169:Portal Vein / Q000196:embryology / Q000502:physiology*; D011446:Prospective Studies; D011673:Pulsatile Flow / Q000502:physiology; D012016:Reference Values; D013157:Splenic Artery / Q000196:embryology / Q000502:physiology*; D018615:Ultrasonography, Doppler, Color; D018617:Ultrasonography, Doppler, Pulsed; D016216:Ultrasonography, Prenatal; D014664:Vasodilation / Q000502:physiology