Assessing Renal Blood Flow Hemodynamics And Autoregulation In Humans Using Intrarenal Doppler Flow Velocity Measurement

Renal hemodynamics studied in experimental animals (rats, mice, dogs) has revealed that autoregulation of renal blood flow (RBF) is established by myogenic response (MR) and tubuloglomerular feedback (TGF). However, this data has not been available in humans. In this pilot study, we directly measure RBF in humans allowing analysis of MR and TGF characteristics. We assessed RBF at 50 Hz using Doppler-based flow velocity measurements by introducing a FloWire (Volcano) catheter into the renal artery of 5 human subjects who were undergoing cardiac catheterization. RBF was derived from Doppler velocities over 5-10 minutes and renal artery diameter. Renal artery pressure (RAP) was measured in the abdominal aorta at the root of the renal artery. The 5 subjects displayed substantial variations in RAP, allowing assessment of MR and TGF by time series analysis. Overall, RBF showed autoregulatory behaviour (see example). MR and TGF signatures could be identified in the Gain, Coherence and Phase plots. A newly develo...