Local release of renin unveils intrarenal arterial fibromuscular dysplasia

A previously healthy young man developed severe hypertension requiring triple antihypertensive therapy. Initial evaluation identified hyperreninemic hyperaldosteronism, mild hypokalaemia, hypodensity within the right kidney at computed tomography (CT), normal renal arteries at echography. He was referred to Verona ESH Centre were angio-CT revealed significant stenosis of an aberrant branch artery of the right kidney with hypo-perfused area colocalizing with a hypo-oxygenated area, as assessed by BOLD-MR imaging. Super-selective sampling found high plasma renin concentrations only in the vein draining the lower pole of the right kidney. Renal angiography confirmed tightened stenosis of an aberrant branch artery supplying the lower arterial segments, consistent with unifocal medial fibromuscular dysplasia, successfully treated with angioplasty. Investigating extra-renal sites, angio-MR found an S-shaped loop of extracranial left internal carotid artery, consistent with multisite fibromuscular dysplasia. This clinical case underscores the importance of comprehensive functional and imaging tests to identify elusive causes of secondary hypertension.