Differential renal function during angiotensin converting enzyme inhibition in renovascular hypertension

Abstract

Renal function was measured sequentially in 32 patients with proven renovascular hypertension who were treated with the oral angiotensin converting enzyme inhibitor captopril. Renal function was assessed by serial measurement of serum creatinine. Six patients showed acute rises in serum creatinine concentration compatible with acute renal failure. Acute renal failure was confined to those patients with stenosis to a solitary kidney (transplant or native, occurring in 3 of 8 patients) or bilateral renal artery stenosis (occurring in 3 of 13 patients). No rise in serum creatinine concentration was observed in 11 patients with unilateral renal artery stenosis during long-term angiotensin converting enzyme inhibitor therapy. Acute renal failure during angiotensin converting enzyme inhibitor therapy was not related to the degree of blood pressure fall or the plasma angiotensin II level. Eleven patients with renovascular hypertension were followed prospectively with estimation of renal function by 99mTc-diethylenetriaminepentaacetic acid (DTPA) clearance (determined by computer analysis of scintillation camera renography). In six patients with unilateral renal artery stenosis, total 99mTc-DTPA clearance and serum creatinine level remained constant following angiotensin converting enzyme inhibitor therapy, while in five patients with bilateral renal artery stenosis 99mTc-DTPA clearance fell from 40 ± 9 to 27 ± 5 ml/min (p<0.05). Split renal function studies revealed that 99mTc-DTPA clearance fell in most kidneys with stenosed arteries during angiotensin converting enzyme inhibition, including the stenosed kidney from patients with unilateral renal artery stenosis (16 stenosed kidneys studied; change in Tc-DTPA clearance, -7.5 ± 2.7 ml/min). With unilateral disease total clearance was unchanged as function increased in the nonstenosed kidney (6 nonstenosed kidneys; change in Tc-DTPA clearance, +8.2 ± 4.6 ml/min). Serum creatinine concentration returned to pretreatment levels following withdrawal of angiotensin converting enzyme inhibitor therapy in all patients with acute renal failure, and 99mTc-DTPA clearance of stenosed kidney also returned to pretreatment levels in two patients studied following angiotensin converting enzyme inhibitor withdrawal after 2 and 4 months of therapy. These results indicate that orally administered angiotensin converting enzyme inhibitors reduce renal function in kidneys with marked renal artery stenosis. Although the functional impairment was reversible following angiotensin converting enzyme inhibitor withdrawal, the long-term consequences to kidneys that develop functional impairment during such therapy are unknown.