Renal reserve in patients with high blood pressure

The mechanism by which hypertension produces renal damage remains poorly defined. Experimental evidence suggests that glomerular hypertension/hyperfiltration constitutes a potential mechanism by which hypertension leads to chronic renal failure. Renal functional reserve has been used to investigate the presence or absence of hyperfiltration, both in experimental animals and humans. Micropuncture studies using the two-kidney, one-clip hypertension model have shown that glomerular hypertension/hyperfiltration is associated with loss of renal functional reserve. However, loss of renal functional reserve in this experimental model is not always indicative of hyperfiltration because some antihypertensive agents (Verapamil, Losartan) correct glomerular hypertension/hyperfiltration, but do not restore renal reserve. Renal reserve has also been evaluated in patients with essential hypertension. Some investigators have shown that hypertension is associated with loss of renal functional reserve which can be restored in some studies with antihypertensive therapy. However, normal renal reserve has also been shown in hypertensive patients. Altogether, these data suggest that renal functional reserve cannot be used to assess the role of hemodynamic mechanisms in hypertension-induced renal injury. Long-term follow-up studies are required to establish if loss of renal reserve is indicative of risk factors leading to renal failure in patients with systemic hypertension.