title: Doppler-ultrasound measurements in renal allografts depend on the patient's body position.
abstract: BACKGROUND
  Due to anatomical reasons a position-dependent renal allograft artery stenosis is being discussed (e.g. only in patient's upright position). The tortuous course of the allograft artery complicates the direct, angle-dependent measurement of maximum systolic flow velocities (vmax). So indirect signs such as intraparenchymal vmax and resistance index might be helpful, but it is unknown how these values change physiologically when patient's body position changes.
  
  
  METHODS
  We examined renal allografts of 60 patients (38 male, 22 female) with stable graft function using B-Mode-, colour-coded duplex-sonography and pulsed-wave-Doppler. We measured vmax and RI-values of three interlobar arteries in the cortex and allograft artery in the hilus in patients standing upright and in horizontal position. Corresponding values were analyzed for significant differences.
  
  
  RESULTS
  Intraparenchymal RI-values and vmax were significantly reduced in patients upright compared to the horizontal position (16 %, MW=0.59 vs. MW=0.70, p < 0.001 resp. 6 %, MW=30.18 cm/s vs. MW=32.17 cm/s, p = 0.045). Similar results could be detected in the renal hilus.
  
  
  CONCLUSIONS
  Patients with stable graft-function show significant, position-dependent differences of the intraparenchymal and hilar RI-values and maximal systolic flow velocities. These changes of Doppler parameters has to be kept in mind for the correct diagnosis of a position dependent allograft artery stenosis.
authors.affiliation: Abteilung für Nephrologie, Klinikum rechts der Isar, Technische Universität München, Germany. dominik.steubl@lrz.tum.de
authors.forename: Dominik
authors.initials: D
authors.lastname: Steubl
authors.forename: Evangelos
authors.initials: E
authors.lastname: Papachristou
authors.forename: Petra
authors.initials: P
authors.lastname: Wolf
authors.forename: Marcel
authors.initials: M
authors.lastname: Roos
authors.forename: Jens
authors.initials: J
authors.lastname: Lutz
authors.forename: Uwe
authors.initials: U
authors.lastname: Heemann
authors.forename: Konrad F
authors.initials: KF
authors.lastname: Stock
mesh_terms: D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity; D005260:Female; D006801:Humans; D007668:Kidney / Q000098:blood supply* / Q000000981:diagnostic imaging*; D016030:Kidney Transplantation / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D056888:Patient Positioning; D011237:Predictive Value of Tests; D012039:Regional Blood Flow; D012077:Renal Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology; D012078:Renal Artery Obstruction / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D012079:Renal Circulation; D014184:Transplantation, Homologous; D016896:Treatment Outcome; D018608:Ultrasonography, Doppler; D018615:Ultrasonography, Doppler, Color; D018617:Ultrasonography, Doppler, Pulsed