Vascular and Extravascular Volumes of the Kidney of Man

Abstract

Indicator dilution techniques were used to determine the vascular and extravascular volumes of the normal human kidney. Renal volumes were corrected to 1.73 m² and refer to one kidney. The renal blood volume (V_IG) averaged 34.8±3.1 ml; the water contained in the distribution volume of labeled inulin (V_IN^W) averaged 48.8±9.0 ml, and that of tritiated water (V_THO^W) 152±20 ml. V_IN^W was used as an index of the extracellular space of the kidney exclusive of the tubular lumina. V_THOW was interpreted to represent the total exchangeable water content of the kidney. The interstitial volume (ΔV_INT^W) and tubular-cellular volume (ΔV_C^W) were derived and averaged 27.4±6.2 ml and 93.7±14.3 ml, respectively. Correction for recirculation by exponential extrapolation was studied and appears satisfactory. Evidence is presented for the existence of significant fluctuations in renal blood flow during the indicator collection intervals, and it is suggested that renal volumes be based on flows determined from the recoveries of each indicator.