• Definition: idiopathic proliferation of fibrous & muscular (fibromuscular!) tissue in medium & large arteries. This is not inflammatory and not atherosclerotic.
  • FMD is the most common cause of Renal artery stenosis (RAS) in children. If you are looking at a renal arteriogram in a child, think of this first.
  • Renal arteries (60%) > ICA / verts (35%) > external iliac (3%) > visceral (2%)
  • FMD will involve the cervical Internal carotid artery (ICA), but not the Common carotid artery (CCA) and not the intracranial ICA.
    SUBTYPES

(1) medial fibroplasia (85%) = string of beads. MOST COMMON (85%)
(2) intimal (5%) = web-like focal stenosis and post-stenotic aneurysm.
(3) perimedial (10%) = tubular narrowing, irregular stenosis.
(4) mixed

  • Digital subtraction angiography findings (DSA): “string of beads”(85%), 50% bilateral
  • Treatment: balloon/angioplasty if pressure gradient > 15 mmHg across the stenosis
  • COMPLICATIONS: aneurysms & spontaneous renal artery dissection (this is almost pathognomonic)