A critical improvement of the local thermodilution method for measuring renal blood flow in man.

A new catheter with a "pig tail" shaped end has been used for renal venous blood outflow measurement by the local thermodilution method. Left and right renal blood flow were measured in nine hypertensive patients with monolateral renal artery stenosis (previously documented by selective renal angiography). Percutaneous introduction and positioning of the "pig tail" catheter in the renal veins was performed without complications. In all cases no deformities in the dilution curves due to: a) contact of the thermistor with the vessel walls; b) shifting baseline during injection; or c) variable and in homogeneous mixing, were observed. Mean percentage variation of five consecutive renal blood flow determinations was 6% in a flow range 154 to 718 cm3 . min-1. We conclude that the use of "pig tail" catheters represents a critical improvement of the local thermodilution method for measuring renal blood flow.