POSTURAL ADJUSTMENTS AND PROTEIN EXCRETION BY THE KIDNEY IN RENAL DISEASE

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Abstract
Rate of urinary excretion of protein is significantly increased on standing in patients with mild or moderate proteinuria (under 1 mg/minute) and good renal function. Postural effects are less conspicuous in patients with intense proteinuria. Close direct correlation is indicated between alterations in the filtration fraction (often considered a measure of glomerular pressure in the well functioning kidney) and the rate of urinary protein excretion. A standard pattern of hemodynamic adjustment to quiet standing (orthostasis) is demonstrated in the normal, as well as diseased but adequately functioning kidney, involving increase in the filtration fraction (and presumably in intraglomerular pressure). Diurnal variations in renal protein excretion are related to alterations in renal hemodynamics. Greatly augmented proteinuria followed intravenous norepinephrine in chronic nephritis with corresponding increase in the filtration fraction. The concentration of protein in the urine is largely controlled by the rate of urine flow and is in itself, an unreliable index of protein excretion, frequently leading to clinical error.