RENAL ARTERY STENOSIS WITHOUT RENAL ISCHAEMIA

MEASUREMENT OF THE FALL IN THE LEVEL OF PLASMA RADIOACTIVITY AFTER INTRAVENOUS ADMINISTRATION OF RADIOHIPPURAN AS A TEST OF RENAL FUNCTION

The level of plasma radioactivity following a single intravenous injection of (131)I-labelled sodium orthoiodohippurate (radiohuppuran) falls with time in a tri-exponential fashion. The rate of fall of plasma radioactivity after an intravenous injection of radiohippuran was measured over the period 25 to 40 minutes from the time of injection and was expressed as the half-life of radiohippuran. The results suggest that this procedure may provide a valid measure of renal function which is more sensitive than the blood urea estimation but less sensitive than the creatinine clearance.

[Experimental and clinical investigations in pathophysiology of renal artery stenosis (author's transl)]

The effect of renal artery stenosis on the poststenotic hemodynamics is demonstrated and evaluated in the presented experimental and clinical investigation. It is shown that the resistance of a medium sized stenosis is small compared to the total renal resistance. The peripheral resistance which is induced by the stenosis is the essential characteristic in the pathophysiology of the renal artery stenosis and the resulting hypertension. The increasing pressure can be measured primarily in the stenosed artery and later also in the not stenosed side and is seen as an effect of the renin-angiotensin-mechanism. The renal artery flow returns to normal after removal of the experimental stenosis. Likewise the reduction in renal artery flow is normalized by resection of the stenosis in the initial phase of the clinical renal artery stenosis. The induced hypertension is reversed to normal. Since the resistance in the initial phase is essentially limited to the stenosed side the global renal resistance is only little increased. Increased total renal resistance is due to morphological changes in the peripheral vessels. The removal of the stenosis will not be followed by a decrease in bloodpressure. This is to be seen in the data of our clinical cases. The critical limit for an effective operation followed by a decrease in artery pressure is to be seen in a total renal resistance of over 0.25 mm Hg/ml min-1.