RENAL EXTRACTION EFFICIENCY FOR PAH IS COMPARABLE IN ESSENTIAL HYPERTENSION AND RENAL FIBROMUSCULAR DYSPLASIA

Abstract

Objective: Previously, we demonstrated that intrarenal blood flow in most patients with renal fibromuscular dysplasia (FMD) does not differ from that of patients with essential hypertension and patent renal arteries. In the present study, we assessed whether the renal extraction of para-aminohippurate (PAH) as a marker of tubular function was affected by the presence of FMD. Design and method: We studied 136 hypertensive patients who were scheduled for diagnostic renal angiography with arterial and renal venous blood sampling. In all of them, a continuous infusion of PAH was started two hours before the procedure to obtain steady state plasma levels at the time of sampling. Blood was collected simultaneously from the arterial and venous catheter prior to the administration of contrast material. Mean renal blood flow (MRBF) was measured simultaneously using the 133Xenon washout technique. Results: Altogether, 21 patients were diagnosed with renal FMD, 45 with atherosclerotic renal artery stenosis (ARAS) and 70 with essential hypertension (EH). Extraction ratio of PAH (ER-PAH) in the patients with renal FMD averaged 72 + 4% which did not differ significantly from that in patients with EH (74 + 3%). MBRF did not differ between these two groups either. Per contra, in patients with ARAS both MRBF and ER-PAH were significantly lower as compared to the other groups. ER-PAH in FMD patients was not modified by age, sex, height of blood pressure or MBRF. Conclusions: The ER of PAH in patients with renal FMD does not differ from that in EH. Thus, both flow and tubular function are well preserved in FMD when is EH is taken as control. This suggests that the pathophysiological mechanism which contribute to hypertension in FMD are different from those which are active in ARAS.