Background: Atherosclerotic renal artery stenosis (ARAS) reduces renal blood flow (RBF) and amplifies regional kidney hypoxia, but their relationship to tissue inflammation and injury markers is poorly understood. We tested the hypothesis that renal injury, reflected by renal vein levels of neutrophil gelatinase associated lipocalin (NGAL) and inflammatory cytokines monocyte chemoattractant protein-1 (MCP-1) would be magnified with severe occlusive vascular disease in humans with ARAS.
Methods: Inpatient studies performed in patients with ARAS (n=40, 71.3±11% occlusion by CT angiography) or essential hypertension (EH) (n=30), during fixed Na+ intake and ACE/ARB Rx. Single-kidney cortical and medullary perfusion and RBF were measured using multidetector CT, and glomerular filtration rate (GFR) by iothalamate clearance. Tissue deoxyhemoglobin levels (R2*) and fractional kidney hypoxia (% of axial area with R2*>30/s) were measured by BOLD-MRI at 3T.
Results: Single kidney RBF, cortical and medullary perfusion were reduced in the post-stenotic kidney, as was GFR. Renal vein NGAL, MCP-1 and fractional hypoxia were higher in patients with ARAS than EH. NGAL and MCP-1 levels correlated directly with cortical R2* and fractional hypoxia (r = 0.52, P <0 .0001 and r = 0.4, P = 0.0006) and with the degree of artey stenosis (r = 0.37, P = 0.04 and r = 0.35, P = 0.05). GFR correlated inversely with NGAL (r= - 0.5, P <0.0001).
Conclusions: Our results demonstrate that elevated renal venous markers of kidney inflammation (MCP-1) and injury (NGAL) in ARAS are correlated with the severity of tissue hypoxia as measured by BOLD MR, suggesting a possible link between kidney inflammation and hypoxia.