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Fig. 5. Diagram shows how ureteral pressure affects systolic and
diastolic blood flow in larger renal arteries typically insonated during
clinical renal Doppler studies. Each section of figure shows Doppler gate in
conduit (segmental or arcuate) artery, which branches into smaller compliant
vessels downstream. Length of arrow in Doppler gate represents velocity of
blood flow. As shown in Figure
4, changes in ureteral pressure (0 mm Hg in A and B; 60 mm Hg in C
and D) significantly affect arteriolar cross-sectional areas and thus total
blood flow volume. In less compliant, larger conduit arteries, these changes
in blood flow are manifested as cyclic changes in blood velocity. Thus,
relative increase in velocity that occurs at systole (measured using resistive
index) is greater when ureteral pressure is elevated (velocity in A > B,
but C >> D). (Reprinted with permission from
[94])