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Renal Artery Stenosis

Renal Artery Stenosis: Pathogenesis and clinical findings Atherosclerosis: A collection of inflammatory cells, lipids, & Fibromuscular Dysplasia: A rare vascular condition characterized by fibrous connective tissue deposits on the renal artery wall abnormal cellular growth in arterial walls, especially renal & carotid arteries Narrowing (stenosis) of the renal artery Renal Artery Stenosis can be unilateral or bilateral Authors: Samin Dolatabadi, Yan Yu* Reviewers: Meena Assad, Jessica Krahn Timothy Fu, Brooke Fallis, Juliya Hemmett* * MD at time of publication ↓ Pressure perfusing the kidney ↑ RAAS (renin-angiotensin- aldosterone system) activation ↓ pressure gradient in glomerulus ↓ Glomerular filtration rate (GFR) ↑ Secretion of aldosterone Turbulent blood flow through area of stenosis Abdominal bruit on side of affected kidney(s) ↑ Secretion of Angiotensin IIà ↑ Systemic vasoconstriction Hypertension ↑ Expression of epithelial sodium channels in cortical collecting duct ↑ Blood volume within volume- constrained space of blood vessels ↓ Renal blood flowà ischemic renal injury Atrophy and fibrosis of affected kidney(s) Unilateral stenosis à Kidney size asymmetry (≥1.5cm difference) ↓ Positively charged Na+ in lumen à Electronegative lumen compared to the interstitial/tubular epithelial cells K+ follows the electrical gradient and is secreted into the electronegative tubular lumen ↓ Serum K+ concentration Hypokalemia *Note: In unilateral renal artery stenosis, the contralateral (normal) kidney can compensate for the increase in renal perfusion pressure caused by hypertension by increasing sodium excretion (pressure natriuresis), preventing flash pulmonary edema. ↑ NHE3 (Sodium Hydrogen Exchanger 3) activity in proximal collecting tubule ↑ Na+ and water reabsorption from renal tubular lumen into blood vessels Chronic left ventricle pressure overload àLeft ventricle hypertrophy (see Left Heart Failure: Pathogenesis Slide) Systolic dysfunction → ↓ left ventricle stroke volume Normally, ↑ in renal perfusion pressureà↑ Na+ excretion and water loss (pressure natriuresis) In bilateral renal artery stenosis*, ↓ GFRàinability for kidney to ↑ renal Na+ & water excretion à volume overload Acute increase in afterload or preload → sudden ↑ in left ventricular filling pressures → blood backup into lungs Pulmonary vasculature hypertension → ↑ fluid filtration across the pulmonary endothelium into interstitium and alveolar spaces Flash (rapid onset) pulmonary edema Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications Published December 30, 2021 on www.thecalgaryguide.com