The nature of the fluid draining from the kidney, after its artery was occluded, was investigated. Samples of systemic arterial blood, renal venous blood and urine were also analyzed. It was found that the fluid draining from the kidney after occlusion is a mixture of vascular blood and another fluid designated as "diluting fluid," each contributing half to the composite mixture. In volume the mixture is 26 per cent of the functionally distended kidney. With the assumption that the renal extracellular fluid can be considered a simple mixture of blood plasma and a cell-free fluid, the composition of the "diluting fluid" was deduced from the known compositions of vascular blood and total fluid draining. The ratios of its content in a given substance to that in systemic (or renal venous) plasma are: for Na and Ca, 1.0; K, 1.5; Cl, 1.2; PO(4), 2.0; urea, 1.8; plasma protein, 0.3; albumin, 0.4; glucose, 0.4, and osmolarity, 1.2. The fluid bears little or no relation to urine, especially since the urine varied considerably between individual dogs whereas the "diluting fluid" was relatively constant in composition. It was also found that the hematocrit of the fluid draining after arterial occlusion progressively decreased as it flowed out, until the last portion contained only 5 per cent red cells. It is concluded that since renal lymph has approximately the same composition in protein, urea, glucose, and inulin as does "diluting fluid," the latter is, in all probability, renal interstitial fluid. Under the conditions of the experiment, it drains out of the kidney slowly relative to blood drainage. It is large in volume, particularly when compared with the capillaries that nourish it. Its high protein content explains the observation that the kidney is apparently naturally distended with a fluid disproportionately rich in plasma protein.

Animals↗

PubMed1956

Distribution of blood in the functional kidney.

An attempt to measure the distribution of blood in the functional kidney of dogs was made. The method involved the injection of liquid latex rubber into the vascular system at physiologic pressures, fixation of the rubber in situ, and then, after corroding away all tissue, measurement of the volume of the rubber casts. The kidney contains, in its functionally distended state, 14 per cent blood. Of this, 4.5 per cent is apparently in the arteries and some 7 per cent in the veins. The functional engorgement of the cortical interlobular veins (about 4 per cent) is particularly striking, for they form a dense palisade of 40 to 300 micro vessels. These are not seen at the usual autopsy since they have drained out and collapsed. It is pointed out that attempts to describe the blood distribution in the kidney after it has been drained of blood are of dubious value. In the light of these data, also, the nature of the measurement of "intrarenal pressure," accomplished by inserting a needle into the renal parenchyma, may be better understood: it is suggested to be primarily a measure of interlobular venous pressure.

Animals↗

PubMed1956

Mechanism of circulatory failure in fresh and sea water drowning.

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Drowning↗