“…1,2,5 In cases of hypertension and unilateral hydronephrosis, selective renal vein sampling generally shows elevated renin secretion from the affected kidney and suppressed levels from the contralateral side. 5 High preoperative plasma renin levels are predictive of improvement in blood pressure following surgery in hypertensive hydronephrotic patients. 4 The cause for the increased activity of the RAA axis that occurs in hydronephrotic kidneys is unclear, but may, in part, be a consequence of the reduced renal blood flow that occurs as a result of the heightened TGF.…”