Converting enzyme inhibitors and renal function in essential and renovascular hypertension. Converting enzyme inhibitors (CEI) are useful in the treatment of hypertension. However, acute renal deterioration may occur in some conditions in association with the crucial role of angiotensin in the regulation of glomerular filtration rate (GFR), such as volume depletion, severe stenosis of both renal arteries, and stenosis of a single functioning kidney. CEI-induced acute renal failure can develop in the absence of a fall in systemic pressure, is facilitated by prior sodium depletion, and is reversible upon discontinuation of treatment. In a personal study conducted in 28 patients with CEI-induced renal dysfunction (reversible after discontinuation of CEI), the incidence of stenosis of large renal vessels was 61%, whereas 39% of these subjects had no significant renal artery abnormalities. Although the occurrence of such a complication is not a convincingly accurate predictor of the existence of renovascular hypertension, angiographic detection of renal artery stenosis (bilateral or on a single-functioning kidney) may be justified in some of these patients. 