Fractional excretion of sodium – a simple test for the differential diagnosis of acute renal failure

We were able to confirm previous studies demonstrating that administration of thyroxine is capable of ameliorating the severity of acute nephrotoxic renal failure in the rat. Nephrotoxic acute renal failure was induced by the subcutaneous injection of potassium dichromate (6.25 mg/kg) into Sprague-Dawley rats. Twenty-four hours after this injection, rats received an intraperitoneal injection of either thyroxine (80 micrograms/kg body wt) or normal saline. Forty-eight hours after the potassium dichromate injection, renal clearance studies were performed. Inulin clearance was significantly higher in the thyroxine-treated than in the saline-treated acute renal failure rats: 1.12 +/- 0.13 (SEM) mL/g versus 0.75 +/- 0.07 mL/min/g kidney wt (P = 0.025). Thyroxine treatment also effected an increase of p-aminohippuric acid extraction from 0.23 +/- 0.03 to 0.33 +/- 0.02 (P = 0.011) and a decrease in the fractional excretion of sodium from 0.38 +/- 0.21 to 0.11 +/- 0.03% (P = 0.037 by Mann-Whitney U test). In order to investigate one potential mechanism of the beneficial effect of thyroxine we studied renal tubular regeneration in this model of acute renal failure. Renal cortical uptake of labeled thymidine into DNA was significantly increased 48 h after the injection of potassium dichromate, and thyroxine administration further enhanced this repair process: 53.9 +/- 3.6 versus 81.4 +/- 5.3 dpm/200 pg of DNA (P = 0.0033).

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Fractional excretion of sodium as a guide to volume depletion during recovery from acute renal failure

Journal of Critical Care ◽

10.1016/0883-9441(87)90096-7 ◽

1987 ◽

Vol 2 (4) ◽

pp. 312

Keyword(s):

Renal Failure ◽

Acute Renal Failure ◽

Fractional Excretion ◽

Volume Depletion ◽

Fractional Excretion Of Sodium

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Low fractional excretion of sodium with contrast media-induced acute renal failure

Archives of Internal Medicine ◽

10.1001/archinte.140.4.531 ◽

1980 ◽

Vol 140 (4) ◽

pp. 531-533 ◽

Cited By ~ 9

Author(s):

L. S. Fang

Keyword(s):

Renal Failure ◽

Acute Renal Failure ◽

Contrast Media ◽

Fractional Excretion ◽

Fractional Excretion Of Sodium

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Course and pathogenesis of postischemic acute renal failure in the rat

AJP Renal Physiology ◽

10.1152/ajprenal.1988.255.2.f257 ◽

1988 ◽

Vol 255 (2) ◽

pp. F257-F264

Author(s):

Y. Yagil ◽

B. D. Myers ◽

R. L. Jamison

Keyword(s):

Renal Failure ◽

Acute Renal Failure ◽

Renal Artery ◽

Creatinine Clearance ◽

Proximal Tubule ◽

Fractional Excretion ◽

Renal Ischemia ◽

Severely Injured ◽

Ischemic Insult ◽

Fractional Excretion Of Sodium

The effect of 45-min clamping of the renal artery was studied in the conscious uninephrectomized rat to reproduce the syndrome of hemodynamically mediated acute renal failure in humans after a single ischemic insult. Twenty-four hours after ischemia, creatinine clearance was reduced by 90%, whereas fractional excretion of sodium was markedly increased; over the subsequent 5 days, both values returned to normal. The animals were nonoliguric. Fractional clearances of graded sizes of neutral dextrans (radii 20–44 A), employed to detect transtubular backleak of inulin, were not significantly different 24 or 48 h postischemia from those in normal animals. The implication that the normal fractional dextran clearances excluded tubular backleak was tested directly by microinjecting [methoxy-3H]inulin into the proximal tubule. In most tubules injected, the recovery of radioactivity in the urine was markedly lower 24 and 48 h postischemia than that in normal rats; in a few injected tubules of postischemic kidneys, recovery was not different from that in normal animals. The low recovery of radioactive inulin was accounted for, at least in part, by transtubular backleak, as shown in experiments in which rats subjected to renal ischemia were cross-transfused with normal animals. These studies indicate that, despite the normal fractional dextran clearances, most tubules were severely injured as shown by tubule backleak of inulin.

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