The normal range of Doppler findings in native kidneys has not been studied extensively. This study correlates changes in Doppler resistive index (RI) Doppler arterial waveform analysis is based on the changes in flow velocity created by pulsatile arterial perfusion. The ratio of systolic to diastolic velocity is determined in large part by downstream resistance . 16 With increasing resistance, the diastolic velocity falls relative to the systolic value. The resistive index was designed as a mathematical index proportional to ar· terial resistance, and it equals the peak systolic frequency shift minus the peak end-diastolic shift divided by the peak systolic shift. MATERIALS AND METHODSThis study consisted of two series of patients. In a small preliminary investigation, measurements were made to determine the spatial and temporal variability of serial waveforms obtained on a given kidney. Information from this pilot study was used to develop an efficient examination technique for the second, larger clinical study designed to evaluate normal age variation.The preliminary study examined 24 kidneys in 12 patients with no known renal disease. In these patients, three individual waveform measurements were made

The Doppler Rl, measured in a blinded fashion, was correlated with RBF, RVR, and GFR calculated by simultaneous clearance measurements. Nine hyper• tensive patients were studied weekly while receiving increasing doses of the vasodilator minoxidil. In 36 studies, RI was significantly correlated with RBF (r = were adjusted for ERV, correlations strikingly improved and were further improved by adjustment for pulse pressure. The ARI allowed semiquantitative predictions of RBF and RVR more accurately than blood urea nitrogen or serum creatinine levels. Cor· relation with GFR was weak. KEY WORDS: Doppler Ultrasonography; Blood flow; Kidneys. over a period of 1.5 to 3 hours.t We postulated that the Doppler RI could be useful as a rapid noninvasive estimation of RBF and RVR.-The Doppler estimation of resistance is based on a relative decrease in diastolic velocity compared to systolic velocity seen with increasing vascular resistance. The RI is a mathematical model for resistance in which the difference between systolic and diastolic Doppler frequency shifts is divided by the systolic shift (lsystolic·diastolic]/systolic). As resistance increases, the diastolic proportion decreases and the index value increases, reaching 1.0 when diastolic flow ceases. In vitro and in vivo animal studies have demonstrated strong correlation between RBF, RVR, and Doppler Rl. 2 ·3 The quantitative relationship of Doppler RI to RBF, RVR, and GFR has not been previously studied in humans, however. To determine if RI type measurements could provide quantitative estimates of these hemodynamic pa· rameters, we studied the correlation of RI measurements with RBF, RVR, and GFR values calculated by simultaneous inulin and para-aminohippurate clearance.

Ejection-phase indexes of LV function were reduced by cocaine in this model of conscious, sedated dogs, but effects were attributable to increased wall stress rather than to reduced myocardial contractility. These effects persisted for at least 2 hours after the infusion was stopped.

This study demonstrates that when vascular resistance is low, peak systolic velocity and peak flow volume increase with increasing blood pressure. We used ischemia with reactive hyperemia to create reproducible low resistance conditions in 32 volunteers. Ischemia resulted in sharp increases in systolic and diastolic velocities, while the difference between these velocities increased minimally. Spontaneous variations in subject's systolic blood pressure were positively correlated with peak sys-R ecent reports have shown excellent results in distinguishing malignant from benign ovarian masses by high Doppler shift frequencies and low Doppler index values (RI, PI).t· 3 In other studies, malignant and benign lesions have shown overlap of these measurements.4. . . ' 5 We speculated that systemic BP might be an uncontrolled variable in study populations, accounting for some of the observed inconsistency. To evaluate the potential effect of BP, we used a low resistance is- We conclude that low resistance flow is blood pressure dependent. Because blood pressure increases with age, tumor velocity and frequency shift thresholds may need blood pressure correction if applied over wide age ranges. The resistive index was independent of blood pressure and thus may be preferable. KEY WORDS: Doppler ultrasonography; Blood flow; Blood pressure; Neoplasm. chemic model in normal volunteers to simulate low resistance tumor flow. Under these conditions, we characterized the relationship between spontaneous variations in systemic BP found among our subjects and the corresponding variations in Doppler sonographic measurements of velocity, flow volume, and Rl. SUBJECTS AND METHODSWe studied 32 volunteers (21 male and 11 female) between the ages of 24 and 53 years. None had a history of heart disease, anemia, or use of vasoactive drugs.The subjects were examined while resting supine. The systemic BP was estimated by auscultation of systolic and diastolic Korotkoff's sounds in the brachial artery below a blood pressure cuff on the right upper arm.For the study of Doppler flow during reactive hyperemia, the BP cuff was placed on "the upper right forearm of the subject. A transverse gray scale sonographic image 10 em above the elbow was used to

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