title: Renal vein Doppler sonography of obstructive uropathy.
abstract: OBJECTIVE
  Obstructive uropathy in the early stages can be difficult to diagnose using either standard sonography or the arterial resistive index. We tested the hypothesis that acute obstruction of the renal collecting system reduces the intraparenchymal renal compliance, which affects the intraparenchymal venous blood flow to a greater degree than the arterial flow.
  
  
  METHODS
  Twelve patients with clinical evidence of acute obstructive uropathy were referred for helical CT to confirm the diagnosis and to provide a gold standard by which we could evaluate the sonographic findings in the 12 test patients. Twelve patients without renal disease served as a control group. Doppler sonography of the interlobar arteries and veins of both kidneys then was performed, with the sonographer unaware of which kidney had an obstruction. Peak venous flow measurements and arterial resistive and venous impedance indexes were obtained. The impedance indexes of the obstructed and unobstructed kidney were compared for each patient.
  
  
  RESULTS
  The mean arterial resistive indexes of the obstructed kidneys were larger than those of the unobstructed kidneys, 0.67 +/- 0.08 and 0.62 +/- 0.05, respectively (p = 0.05). The venous impedance indexes comparing obstructed and unobstructed sides were 0.38 +/- 0.25 and 0.80 +/- 0.25, respectively, a statistically significant result (p = 0.0002). On average, the peak venous flow signal in the obstructed kidney was 69% higher than that of the unobstructed kidney (p = 0.04) and 86% higher than that of the peak venous flow signal in the control group (p = 0.005).
  
  
  CONCLUSIONS
  Renal obstruction alters the venous flow to a greater extent than the arterial flow, and a comparison between the venous flow in the obstructed and unobstructed kidneys may improve diagnostic accuracy.
authors.affiliation: Discipline of Medicine, University of Newcastle, Callaghan Campus, Callaghan, New South Wales, 2308 Australia.
authors.forename: Grant A
authors.initials: GA
authors.lastname: Bateman
authors.forename: Ramesh
authors.initials: R
authors.lastname: Cuganesan
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity; D005260:Female; D006801:Humans; D006869:Hydronephrosis / Q000000981:diagnostic imaging* / Q000209:etiology; D008297:Male; D008875:Middle Aged; D012077:Renal Artery / Q000000981:diagnostic imaging; D012082:Renal Veins / Q000000981:diagnostic imaging*; D018608:Ultrasonography, Doppler; D014517:Ureteral Obstruction / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology; D014655:Vascular Resistance