Effect of chronic ACE inhibition on the diagnostic value of renography for renovascular hypertension: a preliminary report.

We compared the effects of acute and chronic ACE inhibition (ACEi) on the 123I-hippurate in the stenotic kidney of two 2-kidney, 1-clip hypertensive dogs. In the period after clip implantation poststenotic renograms without ACEi of both dogs were normal. Acute ACEi always resulted in delayed hippurate handling. Chronic ACEi, however, induced abnormal poststenotic renograms in only 36% of the cases. Withdrawal of chronic ACEi restored the phenomenon of acute ACE-induced delayed hippurate handling within 5 months in both dogs. These data indicate that chronic ACEi or recent ACEi medication reduces the effectiveness of ACEi renography in diagnosing hypertension due to a moderate renal-artery stenosis. This phenomenon may explain why the sensitivity of ACEi renography in human studies varies more than in animal studies.