The kidney is the primary organ in the excretion of the waste products of catabolism. But they also play an essential role in the maintenance of acidbase -balance, a normal electrolyte and water content of the blood and tissues and a constant volume of the fluid compartments. The tubules of the kidney reabsord approximately 180 liters of Water per day and selectively reabsorb those electrolytes and other materials which the body requires.Another important function of the kidney is to reabsorb sodium and chloride as well as other ions. In addition to the -excretion of waste products and the maintenance of the body stores of water and electrolytes, the kidney has a critical role in the maintenance of acid-base balance.
The respiratory system participates by stabilizing the plasma carbonic acid level at from 1.25 to 1.35meq/lt. and the kidney ordinarily stabilizes the alkali reserve, so, as we have seen the normal ratio of the bicarbonate, to the carbonic acid, being 20: 1, results in the normal pH of 7.4.
For the kidney to maintain the normal alkali reserve it is necessary to conserve base. First, base is conserved by the conversion of the dibasic to the monobasic phosphate by the, substitution of an hydrogen ion for a sodium ion and its -reabsorption.
Second, base combined with inorganic acid, in the tubules, may be, replanced by´,hydrogen ions, and thirdly. The kidney forms ammonia which it substitutes for fixed base in the neutralization of acids excreted in the urine.
Numerous. studies have been carried out to evaluate the functions of the kidneys, However, the most commonly used renal function tests may be listed. 1) Nonprotein nitrogen determination
2) Blood urea nitrogen determination
3) Creatinine determination
4) P.S.P, test
5) Urine concentration test
6) Intravenous pyelography
7) Urea clerance test
Urea clerance, the blood N.P.N. Concentration, B.U.N. determination, and creational a determination may give a gross but practical evaluation of "Glomerular filteation rate. "The measurement of the maximal urinary specific gravity, utilizing a period of dehydration, serves as a measure of tubular reabsorptive capacity. The excretion of P.S.P. serves as a measure of tubular excretory capacity, in conclusion, proteinuria may occurs as a result of lordosis or an asumption of the erect posture, if constant throughout the day and night and in excess of 0.2 gm. Per day, proteinuria in, the absence of cardiac failure or fever is evidence of renal disease, and the excretion off urine of a fixed specific gravity 10.10 which is equal to that of the glomerular filtrate is also evidence of severe renal diseas.
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