title: Evaluation of renal cortical perfusion by noninvasive power Doppler ultrasound during vascular occlusion and reperfusion.
abstract: BACKGROUND
  Urine output, a frequently used resuscitation end point, is presumed to represent renal cortical perfusion. However, no noninvasive method for direct measurement of renal perfusion exists. Power Doppler ultrasound (PDUS) is a method that reportedly is sensitive to low-velocity and microvascular blood flow and can depict it. This study aimed to develop a quantitative technique for PDUS image analysis, and to evaluate the ability of PDUS to quantify cortical perfusion during renal ischemia induced by vascular occlusion.
  
  
  METHODS
  A method was developed to determine the mean gray-scale intensity of PDUS images from within the renal cortex (PDUS image intensity). This index was hypothesized to represent renal cortical microvascular blood flow. Renal cortical blood flow was determined using fluorescent microspheres in five swine. Renal artery flow was measured with an ultrasonic flow probe. Power Doppler ultrasound was performed at baseline; at 75%, 50%, and 25% of baseline renal artery flow; and during reperfusion.
  
  
  RESULTS
  Subjectively, PDUS images showed decreases in image intensity corresponding to renal artery occlusion and increases after reperfusion. Cortical blood flow correlated well with renal artery flow (n = 25; r2 = 0.868) and with PDUS image intensity (n = 25; r2 = 0.844).
  
  
  CONCLUSIONS
  Noninvasive power Doppler ultrasound image intensity correlated well with invasively measured renal cortical blood flow, and may be useful during resuscitation of injured and critically ill patients.
authors.affiliation: U.S. Army Institute of Surgical Research, Fort Sam Houston, TX, USA.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kuwa
authors.forename: Leopoldo C
authors.initials: LC
authors.lastname: Cancio
authors.forename: Jill L
authors.initials: JL
authors.lastname: Sondeen
authors.forename: Natalya
authors.initials: N
authors.lastname: Matylevich
authors.forename: Bryan S
authors.initials: BS
authors.lastname: Jordan
authors.forename: Albert T
authors.initials: AT
authors.lastname: McManus
authors.forename: Cleon W
authors.initials: CW
authors.lastname: Goodwin
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology; D007091:Image Processing, Computer-Assisted; D007511:Ischemia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D007672:Kidney Cortex / Q000098:blood supply* / Q000000981:diagnostic imaging; D008297:Male; D008833:Microcirculation / Q000000981:diagnostic imaging / Q000503:physiopathology; D012016:Reference Values; D012039:Regional Blood Flow / Q000502:physiology; D012078:Renal Artery Obstruction / Q000000981:diagnostic imaging* / Q000503:physiopathology; D015427:Reperfusion Injury / Q000000981:diagnostic imaging* / Q000503:physiopathology; D012680:Sensitivity and Specificity; D013552:Swine; D018616:Ultrasonography, Doppler, Duplex