Noninvasive investigation for renal artery stenosis: contrast-enhanced magnetic resonance angiography and color Doppler sonography as compared to digital subtraction angiography.

INTRODUCTION: The question about the most appropriate non-invasive method for detecting a renal artery stenosis (RAS) when comparing contrast enhanced magnetic resonance angiography (MRA) and color Doppler sonography (CDS) is still under discussion. Therefore we conducted a prospective study in order to evaluate both methods as compared to digital subtraction angiography (DSA).

PATIENTS/METHODS: Thirtysix consecutive patients (53,9 +/- 13,7 years) with suspected RAS were investigated. MRA was performed using gadolinium for contrast enhancement. CDS was performed using a 2.5 and 3,5 MHz transducer. A peak systolic velocity (Vmax) >200 cm/sec within renal arteries and/or a side to side difference of the resistive index (RI) of >0,05 were used to discriminate stenosis. A diameter reduction of > or = 60% by DSA was considered a stenosis relevant to the patient.

RESULTS: Sixty-eight main renal arteries and 9 accessory vessels were detected by DSA. Twenty main and 3 accessory arteries were found to be stenosed > or = 60%, while 4 main and 1 accessory artery presented with occlusion. MRA detected 70 renal vessels (65 main and 5 accessory arteries). Twenty-one stenosed arteries and 4 occluded vessels were correctly diagnosed by MRA. With CDS 68 renal vessels (62 main and 6 accessory arteries) could be visual- ized out of which 21 stenoses were diagnosed because of increased Vmax and 6 stenoses were detected because of a side to side difference of RI. For main renal arteries sensitivities and specificities were 96% and 86% for MRA and 96% and 89% for CDS.

CONCLUSIONS: MRA and CDS are both comparable methods for detection of a renal artery stenosis > or = 60%. Despite several limitations, CDS can at the moment still be favored as a screening method.