[Investigations on 131I-hippurate-clearance in obstructive-uropathy; extraction of para-aminohippuric acid and 131I-hippurate in the acutely obstructed canine kidney (author's transl)].

The results of more recent clinical and experimental investigations have thrown doubt on the usefulness of determining the individual 131I-hippurate clearance for evaluation of the function of acutely obstructed kidneys. There is a significant difference (5% level) between the kidney performance determined with external measurement on the one hand and with PAH and 125I-hippurate clearance in the steady state on the other. With the steady state method, the restriction of function to be expected in consequence of urinary obstruction is demonstrated, whereas with simultaneous measurement with catheterless 131I-hippurate clearance, an increase in function is detected. In the clearance studies carried out in the conventional way with PAH and 125I-hippurate, it was difficult to determine quantitatively the urine produced during urinary obstruction. The renal extraction of p-aminohippuric acid and 131I-hippurate was therefore determined in simultaneous measurement in six dogs before and after acute urinary obstruction with a constant plasma level of the test substances. The results obtained with this very elaborate method which is, however, independent of urine collection show that an acute urinary obstruction leads to a decrease of renal extraction both of PAH and of 131I-hippurate. Since with conventional clearance, the measurement result is proportional to the amount of substance excreted with the urine, a restriction of function must also result with the steady state methods in determining the performance of acutely obstructed kidneys. The results of the extraction investigations hence confirm the results of the clearance studies mentioned. In addition, they show that the "increase" of renal performance immediately after an experimentally induced urinary obstruction repeatedly found with catheterless determination of 131I-hippurate-clearance cannot be explained by a different kinetic behavior of PAH and 131I-hippurate in the acutely obstructed kidney.