title: Dependence of renal blood flow on renal artery stenosis measured using CT angiography.
abstract: OBJECTIVE
  The present study investigates the suitability of computed tomography angiography (CTA) depicting the degree of renal artery stenosis for estimating renal blood flow (RBF) in a kidney.
  
  
  METHODS
  We investigated renal artery stenosis assessment by CTA in eight adult female hybrid pigs with an ultrasound probe implanted at the renal vein for RBF measurement. An inflatable metal-free cuff was placed around the renal artery to control the RBF. The RBF was then reduced in four steps. For each reduced RBF value and baseline RBF, CTA with a reconstructed slice thickness of 0.625 mm was performed in the arterial phase following injection of 80 ml of nonionic intravenous contrast medium. The radius of the stenotic and non-stenotic renal artery segment was measured in the reconstructed images.
  
  
  RESULTS
  A significant linear correlation (p < 0.0001) was found between the relative apparent stenosis (calculated as the ratio of the radii of the actual stenotic segment and a non-stenotic renal artery segment) and RBF. The linear regression yielded a slope of 0.57 and a y-axis of 24.1 %. A significant linear correlation (p < 0.0001) was also found between the relative true stenosis (the ratio of the radii of the actual stenotic segment and a non-stenotic renal artery segment at baseline) and the RBF. The linear regression yielded a slope of 0.67 and a y-axis of 13.8 %.
  
  
  CONCLUSIONS
  The results show that the relative stenosis apparent on CTA differs from the true degree of renal artery stenosis. Nevertheless, the degree of renal artery stenosis determined by CTA provides a reliable estimate of the resulting RBF reduction.
authors.affiliation: Department of Radiotherapy, Charité, Universitätsmedizin Berlin, Campus Virchow Klinikum, Berlin, Germany. lutz.luedemann@charite.de
authors.forename: L
authors.initials: L
authors.lastname: Lüdemann
authors.forename: B
authors.initials: B
authors.lastname: Nafz
authors.forename: F
authors.initials: F
authors.lastname: Elsner
authors.forename: C
authors.initials: C
authors.lastname: Grosse-Siestrup
authors.forename: M
authors.initials: M
authors.lastname: Meissler
authors.forename: P
authors.initials: P
authors.lastname: Persson
authors.forename: M
authors.initials: M
authors.lastname: Gutberlet
authors.forename: P
authors.initials: P
authors.lastname: Lengsfeld
authors.forename: M
authors.initials: M
authors.lastname: Voth
mesh_terms: D000792:Angiography / Q000379:methods*; D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D001810:Blood Volume / Q000502:physiology; D005260:Female; D006706:Homeostasis / Q000502:physiology; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D017711:Nonlinear Dynamics; D012078:Renal Artery Obstruction / Q000000981:diagnostic imaging*; D012079:Renal Circulation / Q000502:physiology*; D013223:Statistics as Topic; D013552:Swine; D036542:Tomography, Spiral Computed / Q000379:methods*; D014655:Vascular Resistance / Q000502:physiology; D014661:Vasoconstriction / Q000502:physiology; D014664:Vasodilation / Q000502:physiology