Renovascular Hypertension (RVH) part1: Etiology

wadood aref April 15, 2020




  • RVH (HTN) is one of the most common causes of secondary HTN.
  • 5% of all HTN.
  • RVH is due to significant RAS (> 60% of lumen).
  • Significant renovascular disease (RVD) (RAS) →
  1. RVH.
  2. Ischemic nephropathy (due to long standing renal hypoperfusion→ irreversible nephrosclerosis) with poor response to revascularization.

ETIOLOGY 

·      Common causes of RVH: atherosclerosis and fibrodysplasia.
1. Atherosclerosis (ARVD) (70% of RVH)
  • The most common cause of RAS → RVH and RVD.
  • Males more (2:1) (arteriosclerosis more in the males).
  • elderly with HTN, CAD, PVD and CHF.
  • site: lesions at RA ostium from aorta or in proximal 1/3 RA.
  • These lesions often represent “aortic spillover” lesions and are a continuation of the atherosclerotic disease in the aorta as it enters the RA ostium.
  • bilateral is common.
  • progression is common, especially for HTN and atherosclerosis in other parts of the body.
  • rarely complete RA occlusion (despite progress).
 2. Fibro-dysplasia (Fibromuscular dysplasia) (FMD) (30% of RVH)
  • 2nd common cause of RVH.
  • Def: non-atherosclerotic, non-inflammatory disease affecting medium-sized arteries (as renal arteries) causing abnormal growth of wall.
  • Incidence: <0.5% of population (uncommon).
  • Females young - middle age.
  • Bilateral
  • No progression.
  • site: lesion in distal 2/3 of RA and segmental branches.
   Types: according to affected layer (intimal, medial, and perimedial).
Intimal FMD
Medial FMD
Perimedial (adventitial) FMD
5%
80% (most common)
15%
Male = female.
infants and younger adults.
Females : males= 4:1
Females (almost all)
Etiology: unknown,   
Congenital: focal proliferation of fetal arterial remnants.
Acquired: after trauma or intraluminal injury to the vessel.
part of a systemic arterial process (affecting renal, carotid, and iliac arteries).
Although lesion may be solitary,


Angio: smooth focal stenosis of main RA, rarely in segmental vessels.
Affects intima only 

Angio: string of beads (multiple stenoses with intervening aneurysmal dilations).
bilateral in 40%.
Main RA and can extend into the segmental branches.
affect the main RA as focal stenoses or multiple constrictions without mural aneurysms.

·      Uncommon causes of RVH:
3. Developmental RAS:
  • failures of complete development of  RA
  • 40% of childhood RVH.
4. RA aneurysm (RAA):
  • HTN is a common clinical presentation of RA aneurysm.
·         Etiology of RVH with RAA: arterial stenosis, dissection of the artery, AVF formation, thromboembolism, or compression of arterial branches by the aneurysm.
 5. RA dissection:
·         severe HTN as the kidney becomes ischemic.
·         Etiology:
1.   iatrogenic from catheter injuries or trauma.
2.   Spontaneously: complication of ARVD or FMD.
 6. RA embolism:
  • rare.
  • most common etiology is embolism from the left heart.
  • CP: flank pain, HTN, and hematuria.
 7. Takayasu arteritis and giant cell arteritis:
  • Takayasu is common in Asia
  • young women.
  • Affect aorta and its distal branches.
  • RAS and RVH may occur,
  • Med. ttt: steroid suppression with cytotoxic agents.
  • Surgery: Angioplasty or surgical revascularization (if failed medical ttt).
 8. Transplant RAS:
  • Etiology: anastomotic stenosis (commonest), atherosclerosis, FMD, chronic rejection, and kinking (due to significant functional stenosis).
·         CP: worsening or refractory HTN, insidious graft dysfunction, and volume overload (pulmonary edema).