Ports of sufficient recovery of renal function after renal revascularization to discontinue dialysis. [ 30 and 31 ]       pathophysiology   the kidney plays a central role in the regulation of blood pressure. viagra generic The importance of the renin-angiotensin-aldosterone system for the generation of the hypertension is well recognized. However, the mechanisms of the hypertension in patients with renal artery stenosis are complex because not all patients with renovascular disease, especially not with atherosclerotic renal artery stenosis, have (renin-dependent) renovascular hypertension. viagra for sale [ 7 ] in patients with severe bilateral renal artery disease or stenosis of a single functioning kidney, volume overload with secondary suppression/normalization of the plasma renin activity is an important mechanism for the maintenance of the hypertension. Another important mechanism is renal parenchymal hypertension owing to hypertensive nephrosclerosis, renal hypoperfusion owing to congestive heart failure, atheroembolic disease, diabetes mellitus, and so forth. viagra yahoo There is considerable overlap between renovascular and renoparenchymal hypertension in patients with atherosclerotic renal artery stenosis, which may be coincidental to the hypertension rather than causal. [ 32 ]       when the renal perfusion pressure is decreased such as downstream of a hemodynamically relevant renal artery stenosis intrarenal compensatory mechanisms are activated to maintain the glomerular filtration rate (gfr) despite the reduced perfusion. This intrarenal counterregulation is characterized by an increased filtration fraction through the constriction of the efferent arteriole of each glomerulum while the afferent arteriole is dilated. The efferent arteriolar constriction is mediated by angiotensin ii, whereas the afferent arteriolar dilatation is mediated by vasodilatory prostaglandins. does viagra compared viagra These regulatory mechanisms of the glomerular hemodynamics explain the increased risk for acute renal failure owing to the administration of ace inhibitors (and angiotensin receptor blockers, although there are fewer published data) and/or nonsteroidal anti-inflammatory drugs in these patients. viagra for cheap The administration of an ace inhibitor blocks the angiotensin ii effect on the efferent arteriole and causes a precipitous decrease in the gfr. cheap viagra on line This drop in the gfr may not be apparent clinically if the nonstenotic contralateral kidney can compensate the reduction of gfr in the poststenotic kidney. viagra online   in addition to the renin-angiotensin-aldosterone system, several other mechanisms contribute to the pathogenesis of hypertension in renal artery stenosis including the sympathetic nervous system,[ 33 and 34 ] nitric oxide, [ 35 and 36 ] and endothelin. buy genuine pfizer viagra uk [ 37 and 38 ] the relative importance of the different systems is not clear. There is experimental evidence that oxidative stress is increased in reno. viagra in canada without prescription