Blood flow to the avian kidney: The use of transit-time ultrasonic flow probes

A simplified model was used to assess blood flow to the kidney of the anaesthetised domestic fowl. The left kidney was intact and the right kidney consisted of the caudal division with associated vasculature. Transonic perivascular flow probes were placed around the right proximal ischiadic artery and renal vein. Snares around the caudal renal portal vein, common iliac vein and proximal ischiadic artery of the right kidney allowed manipulation of arterial and portal blood flow. Reduction of the pressure in the right renal artery to 50 mm Hg decreased right kidney arterial plasma flow and glomerular filtration rate (GFR). The plasma flow in the right renal vein and the clearance of para-aminohippuric acid by the right kidney remained unchanged. The true filtration fraction of the right kidney, determined from the ratio of GFR to the arterial flow increased slightly. Portal plasma flow and arterial plasma flow contributed 57% and 43%, respectively, to total renal plasma flow during normal arterial and portal flow. J. Exp. Zool. 284:15–22, 1999. © 1999 Wiley-Liss, Inc.