Renal intracortical blood flow distribution, function, and sodium excretion in unanesthetized dogs following vena caval ligation.

We studied the renal function and the intrarenal blood flow of nine dogs whose thoracic inferior vena cava had been previously ligated (caval dogs) and nine other dogs. Following preparative surgery which included placement of a left atrial catheter, a femoral artery catheter, and bilateral ureteral catheters, the caval dogs gained an average of 2.1 kg of fluid weight, whereas the normal dogs gained no weight. Although neither the caval dogs' blood pressure (114 plus or minus 7 vs 120 plus or minus 4 mm Hg) nor their inulin clearance (0.64 plus or minus 0.06 vs. 0.79 plus or minus 0.06 ml/min g-1 kidney weight) was significantly reduced, their estimated renal blood flow (Cpah/[1-hematocrit]) was considerably lower (2.30 plus or minus 0.24 vs. 3.25 plus or minus 0.15 ml/min g-1). During the clearance study, the caval dogs' excretion of sodium (79 plus or minus 18 vs. 158 plus or minus 17 muEq/min) and their fractional clearance of sodium (2.0 plus or minus 0.4 vs. 3.4 plus or minus 0.5%) were reduced. Studies with microspheres failed to demonstrate a selective decrease in blood flow. However, comparison studies of nine other dogs (five caval and four normal) demonstrated that microsphere results were less reproducible in caval dogs than they were in normal dogs. We have concluded taht reduced blood flow is the only consistent alteration of renal function in this edematous animal model and that previous suggestions of altered distribution are not supported by these studies.