Renal artery stenosis

Renal artery stenosis is a narrowing of the artery that carries blood to a kidney, on one side or on both. It matters because it is a cause of secondary hypertension, meaning high blood pressure with an identifiable reason behind it, and one that can sometimes be reversed.

When less blood reaches the kidney, the kidney responds. The renin-angiotensin-aldosterone system, a chain of hormones that raises blood pressure, switches on: the juxtaglomerular apparatus, a small cluster of cells in the kidney, releases renin, and the organ also starts building collateral vessels, alternate routes for blood to get through. The kidney reads the drop in blood flow as scarcity and calls for more pressure.

Almost always the narrowing comes from atherosclerosis, the buildup of plaque in the artery wall, which accounts for about ninety percent of cases; fibromuscular dysplasia, an abnormality of the vessel wall itself, accounts for ten to twenty percent. Over time, that reduced blood supply ends up damaging the structure and function of the kidney.