PROCEDURE FOR CLINICAL EVALUATION OF RENAL FUNCTION

• The procedure described is particularly helpful in evaluating the renal status of patients whose plasma concentrations of nonprotein nitrogen or urea may be but slightly elevated while creatinine clearance values may have fallen as low as 50 or 25 % of normal. This includes many hypertensive patients, in whom the use of hypotensive drugs or sympathectomy may be under consideration. The test involves administering a water load of 2,000 ml. within two hours. This should normally lead to a diuresis of more than 8 ml. per minute. The collection of a blood sample for determination of creatinine, the injection of phenolsulfonphthalein, and the collection of urine samples are all timed in such a way as to yield figures for both glomerular and tubular functional capacity. The mean values for endogenous creatinine clearance by this method were 120 and 100 ml. per minute respectively, in 40 healthy men and 10 healthy women. The normal phenolsulfonphthalein excretion figures ranged from 25 to 45% for the first 15 minutes and from 55 to 80% for total two-hour excretion. The test is obviously contraindicated in the presence of acute renal failure with oliguria; in less severe forms of renal impairment it is informative and avoids the hazards of concentration tests involving restriction of fluid intake.