Screening for Renovascular Hypertension

Abstract

The most common curable cause of high blood pressure is renovascular hypertension. Although hypertension is common in the United States, only a minority, approximately 1%, of patients have a renovascular cause. Using clinical criteria, a subgroup of these patients can be selected in which the prevalence of renovascular hypertension will be approximately 15%. In these selected patients, it is appropriate to proceed to a radiographic screening modality to look for a significant renal artery stenosis. The choice of modality should reflect the strengths and expertise of each specific institution. Hypertensive urography is no longer recommended for screening. Excellent results have been reported with intravenous DSRA in institutions where a strong interest in this procedure exists. Furthermore, intravenous DSRA is easily coupled with the collection of renal vein samples for renin assay. Intravenous DSRA, however, has not maintained widespread use. Although the radionuclide renogram is no longer adequate as a radiographic screening tool, stimulation with an ACE inhibitor, such as captopril or enalaprilat, may produce excellent results. In many institutions, this is the most appropriate examination. Furthermore, it is relatively noninvasive. Merely detecting a significant renal artery stenosis does not, however, mean the patient has renovascular hypertension. Both hypertension and a renal artery stenosis may be present and not be causally related. Because renovascular hypertension is, at least initially, renin mediated, the demonstration of increased renin production by the ipsilateral kidney should confirm renovascular hypertension. Prospective application of these results to patients undergoing revascularization techniques, however, has been disappointing. This may be related to problems in patient preparation, sample collection, renin assay, or even the physiology of chronic hypertension, which is incompletely renin mediated. Thus, offering revascularization only to those patients with lateralizing renal vein renins is not appropriate. If radiographic screening is limited to those patient at greatest likelihood for a renovascular etiology, intra-arterial DSRA or conventional arteriography may be used. These techniques most reliably detect renal artery stenosis. Their main disadvantage lies in their relatively invasive nature, as an arterial puncture is required. The poor predictive value of selective RVRRs implies that revascularization may be attempted without awaiting those results. If percutaneous transluminal renal angioplasty can be performed with a satisfactorily low complication rate, both the diagnostic and the interventional procedure may be undertaken at the same setting. It is expected that further refinements in these diagnostic procedures, particularly with the use of stimulating drugs such as ACE inhibitors, will lead to further improvement in the diagnostic results.(ABSTRACT TRUNCATED AT 400 WORDS)