The mechanisms of elevated blood pressure may be that acute unilateral obstruction can cause hypertension via activation of the renin-angiotensin system whereas bilateral obstruction may elevate blood pressure through volume expansion.[40,41] Another reason was that half the number of patients with obstructive uropathy were older than 65 years; the incidence of hypertension is associated with advancing age. This evidence concerns the gene REN and urinary tract obstruction.