Captopril renal scintigraphy — An advance in the detection and treatment of renovascular hypertension

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We read with interest the recent article by Meier et al. concerning captopril renography and renovascular hypertension.1Meier GH Sumpio B Black HR Gusberg RJ Captopril renal scintigraphy—an advance in the detection and treatment of renovascular hypertension.J Vasc Surg. 1990; 11: 770-777PubMed Scopus (29) Google Scholar We too feel that the test is a major advance in the detection and treatment of patients with suspected renovascular hypertension and agree that it largely supersedes the need to perform selective renin sampling on these patients. We felt their article made many useful points, but we would like to make some additional ones. Renovascular renal failure is now a growing problem with our increasingly elderly population and has an incidence of 14% in our patient population over the age of 50 years who are admitted for renal replacement therapy.2Scoble JE Maher ER Hamilton G Dick R Sweny P Moorhead JF Atherosclerotic renovascular disease causing renal impairment—a case for treatment.Clin Nephrol. 1989; 31: 119-122PubMed Google Scholar Atherosclerotic renal artery stenosis is a progressive condition, and 10% to 17% of these will occlude within 2 to 3 years, and 40% of unilateral renal artery stenosis will proceed to contralateral involvement within 52 months.3Bergentz SF Bergqvist D Weibull H Changing concepts in renovascular surgery.Br J Surg. 1989; 76: 429-430Crossref PubMed Scopus (6) Google Scholar, 4Wollenweber J Sheps SG Davis GD Clinical course of atherosclerotic renovascular disease.Am J Cardiol. 1968; 21: 60-71Abstract Full Text PDF PubMed Scopus (245) Google Scholar, 5Dean RH Kieffer RW Smith BM et al.Renovascular hypertension.Arch Surg. 1981; 116: 1408-1415Crossref PubMed Scopus (280) Google Scholar Although we agree that captopril renography is an accurate predictor of response of hypertension to revascularization, we do not feel that this is of central importance. The major rationale for performing revascularization is preservation of renal function and mass and not the control of the blood pressure.3Bergentz SF Bergqvist D Weibull H Changing concepts in renovascular surgery.Br J Surg. 1989; 76: 429-430Crossref PubMed Scopus (6) Google Scholar, 6Scoble JE Hamilton G Atherosclerotic renovascular disease.Br Med J. 1990; 300: 1670-1671Crossref PubMed Google Scholar Revascularization for hypertension should only be performed when control by medication is impossible or difficult. Surgical revascularization carries major morbidity and mortality rates, as evidenced by the death of three patients treated surgically by Meier et al. and should not be undertaken lightly. Unfortunately Meier et al. have not told us about the renal function in their patients or whether improvements in this occurred after intervention. What captopril renography does is elegantly demonstrate that a stenosis is in fact significant by showing that the renin-angiotensin system is required to maintain renal perfusion. In effect, it unmasks a latent stenosis, which may cause more severe renal impairment in the future. In a patient with a low initial glomerular filtration rate the test is not appropriate, and a decision about revascularization should be made on the basis of angiographic evidence of renal artery stenosis, the presence of a kidney of reasonable size, and the exclusion of other causes of the renal impairment. In a patient with medically controllable renovascular hypertension the diethylenetriaminepentaacetic acid test can of course help diagnostically, but we would then suggest that it can be more appropriately used as a method of follow-up rather than as an indication for intervention. Angiography is dangerous in this group of patients,2Scoble JE Maher ER Hamilton G Dick R Sweny P Moorhead JF Atherosclerotic renovascular disease causing renal impairment—a case for treatment.Clin Nephrol. 1989; 31: 119-122PubMed Google Scholar and captopril-diethylenetriaminepentaacetic acid scanning is a valuable screening test that in our hands has a 88% sensitivity and 70% specificity in detecting renal artery stenosis of 75% or greater (unpublished data). In our practice angiography is now used only when intervention is indicated, with a corresponding reduction in mortality and morbidity rates during the diagnosis and management of these patients. We also felt that the need for care when the test is performed should be emphasized. Captopril is potentially dangerous, and there are many instances where it has precipitated renal failure in a patient with renal artery stenosis. It is our practice to give only 25 mg of captopril, to have an intravenous infusion running, to carry out 5 minute blood pressure checks, and to avoid performing the test on patients who are dehydrated or depleted of sodium. Using this protocol we have carried out over 100 such tests with no serious complications. Thus we endorse the authors' enthusiasm for the test but suggest that relief of hypertension is not a major goal in these patients. Simple precautions should be taken when the test is carried out, and by avoiding angiography it can lead to a decrease in morbidity and mortality rates. This is undoubtably a major advance in the diagnosis and management of renovascular disease.