Detection of renal artery stenosis: Prospective comparison of captopril-enhanced Doppler sonography, captopril-enhanced scintigraphy, and MR angiography

OBJECTIVE. The objective of our study was to compare the value of captopril -enhanced Doppler sonography, captopril-enhanced renal scintigraphy, and ga dolinium-enhanced MR angiography for detecting renal artery stenosis. SUBJECTS AND METHODS. Forty-one patients with suspected renovascular hypert ension were prospectively examined with captopril-enhanced Doppler sonograp hy, captopril-enhanced renal scintigraphy, gadolinium-enhanced MR angiograp hy, and catheter angiography. The sensitivity and specificity of each techn ique for detecting renal artery stenosis measuring 50% or greater and 70% o r greater were compared using the McNemar test. Positive and negative predi ctive values were estimated for populations with 5% and 30% prevalence of r enal artery stenosis. Kappa values for interobserver agreement were assesse d for both gadolinium-enhanced MR angiography and catheter angiography. RESULTS. For detecting renal artery stenosis measuring 50% or greater, the sensitivity of gadolinium-enhanced MR angiography (96.6%) was greater than that of captopril-enhanced Doppler sonography (69%, p = 0.005) and captopri l-enhanced renal scintigraphy (41.4%, p 0.001). No significant difference i n specificity was observed among modalities. For renal artery stenosis meas uring 50% or greater, positive and negative predictive values were respecti vely 62% and 86% for captopril-enhanced Doppler sonography, 49% and 76% for captopril-enhanced renal scintigraphy, and 53% and 98% for gadolinium-enha nced MR angiography. Interobserver agreement was high for both gadolinium-e nhanced MR angiography (kappa = 0.829) and catheter angiography (kappa = 0. 729). CONCLUSION. Gadolinium-enhanced MR angiography is the most accurate noninva sive modality for detecting renal artery stenosis greater than or equal to 50%. The use of captopril-enhanced Doppler sonography in combination with g adolinium-enhanced MR angiography for identifying renal artery stenosis nee ds to be evaluated with a cost-effectiveness analysis.