BLOOD VELOCITY PROFILES IN THE HUMAN RENAL-ARTERY BY DOPPLER ULTRASOUND AND THEIR RELATIONSHIP TO ATHEROSCLEROSIS

Blood velocity profiles were measured in the renal branch (diameter 5. 9 +/- 1.3 mm) of the aortorenal bifurcation using a 20-MHz 80-channel pulsed Doppler velocimeter during retroperitoneal surgery in 10 patien ts. The peak Reynolds number was 1145 +/- 140 and the frequency parame ter (Wormersley parameter) was 3.0 +/- 0.8. immediately distal to the ostium of the renal artery, reverse Bow, indicating flow separation, w as observed near the cranial wall mainly during the first part of the cardiac cycle. There were flows from the cranial to the caudal side of the artery at this location, indicating the presence of strong second ary flows. Two diameters down stream of the ostium, the velocity profi les were skewed to the caudal side in all patients. Four diameters dow nstream, the flow profile was symmetrical (3 patients) or only slightl y skewed (7 patients) and virtually parabolic throughout the cardiac c ycle. These observations mean that the flow on the cranial side df the renal branch of the human aortorenal bifurcation is characterized by (1) a bidirectional oscillation of the Bow, (2) separation of the Bow during systole, and (3) low time-averaged shear rate. These blood velo city patterns may be related to the localization and development of at heromatous plaque that occurs preferentially in this region of the ren al artery. Conversely, the unidirectional, axisymmetrical how found in more distal parts of the renal artery are associated with a very low incidence of lesions.