Magnetic resonance angiography--the procedure of choice to diagnose renal artery stenosis?

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.

Revascularization of renal artery stenosis in patients with renal insufficiency

The incidence and prevalence of end-stage renal disease (ESRD), particularly in the elderly population, have continued to increase in the United States. It is estimated that 10% to 20% of the elderly patients with ESRD have potentially remediable renal vascular disease. The purpose of the present study is to examine the results of renal artery revascularization in 20 patients aged older than 55 years with chronic renal failure (serum creatinine level >2 mg/dL) with proximal renal artery stenosis (RAS) diagnosed by magnetic resonance angiography (MRA) who underwent surgical or percutaneous revascularization. Patients were followed up closely in the postrevascularization period; renal function was monitored and potential complications of the procedure were carefully noted. Four of the 20 patients developed serious complications, including 3 patients with clinically significant atheroembolic disease and 1 patient with renal artery dissection. Seven patients developed greater than 5% eosinophilia. Five of the 20 patients had a deterioration in renal function 3 to 6 months after the procedure, and only 5 patients had a reduction in serum creatinine concentration 3 to 6 months after the procedure. The present study suggests that in elderly patients with chronic renal failure and proximal RAS, revascularization of renal vessels is associated with a high complication rate, and improvement in renal function occurs in only 25% of the patients. Whether revascularization can slow the rate of progression of renal failure remains uncertain and can only be answered by a large prospective trial.

Fibromuscular dysplasia of the renal arteries

Although renovascular hypertension is less common than primary hypertension, it is important for clinicians to recognize this clinical entity because of its distinct pathophysiology and specific therapy. It is estimated that about 5% of the overall hypertensive population have renovascular hypertension. Whereas most renovascular lesions are caused by atherosclerosis, stenosis due to fibrous dysplasia is an important disease. In children and young adults, fibromuscular dysplasia of the renal arteries is the most common cause of renovascular hypertension. This review deals with the pathology, clinical characteristics, diagnosis, and therapy of renovascular hypertension associated with fibromuscular dysplasias.