THE MINIMUM NUMBER OF CARDIAC CYCLES NECESSARY FOR CALCULATION OF RENAL BLOOD-FLOW VELOCITY INDEXES IN PREGNANT AND NONPREGNANT WOMEN

In this study Doppler ultrasound was used to measure the blood flow ve locity in the main and segmental renal arteries in 16 healthy non-preg nant women. There were no differences in blood flow indices between th e right and left kidneys as well as between the main and segmental art eries. The variability of the indices in the main and segmental renal arteries in healthy non-pregnant and in the segmental renal artery in normal pregnant women (32-37 weeks of gestation) was investigated The within-patient error standard deviations of ten cycles and two, and th ree to nine averaged cycles were compared. In non-pregnant women, valu es for the error standard deviation comparable with those obtained fro m ten cycles for the systolic/diastolic ratio and pulsatility index fr om both main and segmental arteries were obtained by averaging from fi ve to six consecutive cycles, while the error standard deviation for t he resistance index stabilized when averaging only two to four cycles. In pregnant women, the error standard deviations for both the systoli c/diastolic ratio and pulsatility index reached quite stable values af ter three cycle had been averaged as did the error standard deviation for the resistance index. We speculate that this difference between no n-pregnant and pregnant women is due to more favorable conditions for renal visualization and consequently higher quality Doppler signals du ring pregnancy. A knowledge about the number of cardiac cycles require d for an accurate calculation of renal blood flow velocity indices may prevent time-consuming calculations and inaccurate conclusions.