Animal studies with unilateral measurements of 131I-hippurate clearance without catheter to determine renal function during ureteral obstruction

In 64 dogs the influence of a sudden unilateral ureteral obstruction on renal blood flow (RBF), on renal extraction of PAH and 131I-hippurate and on kidney function as determined by clearance methods was studied. By measuring the venous blood flow, using the method of Bretschneider, a decrease of the RBF was observed generally although in some cases the RBF remained constant or even increased. The arterial blood flow, controlled by electromagnetic means, showed a tendency to increase but in some cases remained constant or decreased. In all cases, independent of the reaction of the RBF to acute ureteral obstruction, a significant decrease of the renal extraction of PAH as well as of 131I-hippurate was observed. This decrease of kidney function was found by conventional methods (PAH- and 125I-hippurate clearance in 'steady state' technique), whereas by external measurement of the 131I-hippurate clearance different results were obtained leading to the assumption of an increase of renal function. Only if urinary flow was free, the three methods agreed in their results. In kidneys damaged by a longer period of ureteral obstruction, these function tests yielded corresponding values only in the case of unimpaired urinary flow. Following repeated ureteral obstruction, external measurement and conventional methods no longer agreed in kidney function determination. In some cases, by external measurement renal function was determined to be higher before opening the ligation of the ureter as compared to the result achieved thereafter. (orig./WN)