title: The hemodynamics of transjugular intrahepatic portosystemic shunts: investigations with Doppler sonography and development of an in vitro model.
abstract: OBJECTIVE
  We evaluated Doppler sonography-based measurements of transjugular intrahepatic portosystemic shunt (TIPS) function and developed an in vitro model of normal TIPS hemodynamics.
  
  
  METHODS
  We reviewed retrospectively the results of all trans-TIPS manometries (N = 116) performed during a 24-month period. Portosystemic pressure gradient was compared with peak stent velocity as measured by angle-corrected Doppler sonography. A flow phantom simulating TIPS was created using 8-, 10-, and 12-mm-diameter wire-mesh stents placed in cylindrical channels with lengths ranging from 3.4 to 6.0 cm.
  
  
  RESULTS
  Among 50 trans-TIPS manometries with corresponding Doppler sonography performed on well-functioning shunts, measured portosystemic pressure gradient and peak velocity were not correlated (R2 = .014). On the basis of a regression of measurements in the flow phantom, pressure loss in a stented cylindrical channel was estimated as follows: delta p = rho.(0.145 -0.001.Rey + 0.816.L/D).(Vmean2/2), where rho is the fluid density, Rey is the Reynolds number, L is the channel length, D is the stent diameter, and Vmean is the time-averaged velocity within the stent. Predicted and measured pressure gradients were correlated (R2 = .91).
  
  
  CONCLUSIONS
  Peak velocity in patients with a normally functioning TIPS does not predict the magnitude of the portosystemic pressure gradient.
authors.affiliation: Department of Radiology, University of Michigan Hospitals, Ann Arbor 48109, USA.
authors.forename: B L
authors.initials: BL
authors.lastname: Daniel
authors.forename: J M
authors.initials: JM
authors.lastname: Rubin
authors.forename: J B
authors.initials: JB
authors.lastname: Fowlkes
authors.forename: D M
authors.initials: DM
authors.lastname: Williams
authors.forename: R S
authors.initials: RS
authors.lastname: Adler
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology; D004867:Equipment Design; D006083:Graft Occlusion, Vascular / Q000000981:diagnostic imaging / Q000601:surgery; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D007601:Jugular Veins / Q000000981:diagnostic imaging*; D008955:Models, Cardiovascular; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D011170:Portasystemic Shunt, Surgical / Q000295:instrumentation*; D011183:Postoperative Complications / Q000000981:diagnostic imaging* / Q000601:surgery; D012016:Reference Values; D012086:Reoperation; D012189:Retrospective Studies; D015607:Stents; D018608:Ultrasonography, Doppler