Pathophysiology and treatment of posttransplant hypertension.

Post-renal transplant hypertension remains a common problem. The most frequent causes now are chronic rejection and cyclosporine-induced hypertension. Before the development of cyclosporine, renin-dependent hypertension was the dominant pathophysiological mechanism but now, with the widespread use of cyclosporine, a salt-dependent mechanism is the major one. In severe "inappropriate" hypertension, potentially surgically remediable causes such as renal artery stenosis of the allograft artery or renin release from the native kidneys should be considered. Cyclosporine causes hypertension in normal subjects and in all solid organ transplants. The most likely mechanism is renal vasoconstriction with subtle retention of sodium chloride together with systemic vasoconstriction. The vasoconstriction, as yet, is not associated with any specific vasoconstricting agent nor does there appear to be a specific antagonist. Indeed, increased sensitivity to many different vasoconstrictors has been demonstrated. The major site of vasoconstriction appears to be in the afferent arteriole, and optimum antihypertensive therapy is probably provided by calcium channel blockers if the hypertension is due to cyclosporine. Because post-renal transplant hypertension is often multifactorial in origin, however, it is not surprising that the use of combined antihypertensives is often necessary.