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Differences in renal hemodynamics and renin secretion between patients with unifocal and multifocal fibromuscular
Daan J L van Twist1,2,3, Pieter W M de Heer1,2, Alfons J H M Houben1,2
1Department of Internal Medicine.
Objective:
Fibromuscular dysplasia (FMD) can be classified in a multifocal and a unifocal subtype. As unifocal FMD generally leads to more severe hypertension at younger age, we hypothesized that renal hemodynamics are more disturbed in unifocal renal artery FMD as compared with multifocal FMD, leading to increased renin secretion.
Methods:
We measured renal blood flow (Xenon washout method), renin secretion, and glomerular filtration rate per kidney in 101 patients with FMD (26 unifocal and 75 multifocal), all off medication and prior to balloon angioplasty.
Results:
We found that renal blood flow and glomerular filtration were substantially lower in kidneys with unifocal FMD as compared with multifocal FMD. In the affected kidney from patients with unilateral FMD for example, mean renal blood flow was 173 ± 77 in unifocal vs. 244 ± 79 ml/100 g kidney/min in multifocal FMD (P = 0.013). Moreover, lateralization in renin secretion was only observed in a subset of patients with unifocal FMD, but not in any of the patients with multifocal FMD.
Conclusion:
These findings suggest that the impact of unifocal FMD lesions on the kidney is more severe, resulting in a classical pattern of renovascular hypertension. In multifocal FMD, however, renal blood flow is more preserved, local renin secretion is not increased, and the association between renin levels and blood pressure is inverse. These differences may explain the often more severe clinical presentation and higher success rate of revascularization in unifocal FMD, but also suggest that the pathophysiological mechanisms leading to hypertension may differ between these two disease entities.
Insights
Unifocal fibromuscular dysplasia (FMD) more severely impacts renal hemodynamics and renin secretion compared to multifocal FMD. This suggests distinct mechanisms underlying hypertension in these FMD subtypes.
Area of Science:
- Nephrology
- Vascular Biology
- Cardiovascular Disease
Background:
- Fibromuscular dysplasia (FMD) is classified into unifocal and multifocal subtypes.
- Unifocal FMD is often associated with more severe hypertension at a younger age.
Purpose of the Study:
- To investigate differences in renal hemodynamics and renin secretion between unifocal and multifocal renal artery FMD.
- To test the hypothesis that unifocal FMD causes more disturbed renal hemodynamics and increased renin secretion.
Main Methods:
- Renal blood flow, renin secretion, and glomerular filtration rate were measured in 101 FMD patients (26 unifocal, 75 multifocal).
- Measurements were performed off medication and prior to balloon angioplasty using the Xenon washout method for renal blood flow.
Main Results:
- Kidneys with unifocal FMD exhibited significantly lower renal blood flow and glomerular filtration compared to multifocal FMD.
- Mean renal blood flow was 173 ± 77 ml/100g/min in unifocal vs. 244 ± 79 ml/100g/min in multifocal FMD (P=0.013).
- Renin secretion lateralization was observed in some unifocal FMD cases but not in multifocal FMD.
Conclusions:
- Unifocal FMD lesions have a more severe impact on the kidney, consistent with renovascular hypertension.
- Multifocal FMD preserves renal blood flow and does not show increased local renin secretion, with an inverse renin-blood pressure association.
- Differences in pathophysiology may explain clinical presentations and revascularization success rates between unifocal and multifocal FMD.
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