Hypertension and the kidney

Hypertension and the kidney are closely linked in several ways. The kidney normally responds rapidly to changes in blood pressure by alteration of renal haemodynamics and sodium excretion. These functions of the kidney are reset in established hypertension. However, several subtle abnormalities of renal function are demonstrable in normotensive offspring of hypertensive parents, suggesting that the kidney may play a central role in the pathogenesis of essential hypertension--a possibility supported by a number of cross-transplantation studies in different animal models of hypertension. Hypertension itself commonly causes severe renal failure when the malignant phase develops, but the question of whether benign hypertension causes renal impairment remains controversial. Firm data that this is so are in general lacking, although in black subjects hypertensive nephropathy appears to be up to 18-fold more frequent than in whites, and is reported as a common cause of end-stage renal failure. The reasons for this racial difference in susceptibility to hypertensive renal injury remain unknown. Secondary hypertension also commonly develops in patients with underlying renal disease, and the co-existence of hypertension with renal impairment greatly worsens the rate of the deterioration of renal function. Effective treatment of hypertension in renal disease, particularly with converting enzyme inhibitors, is capable of slowing the rate of loss of function, both in animal models and in human disease, though in the latter case this benefit has so far been demonstrated unequivocally only in patients with diabetic nephropathy.