[The screening of renal artery stenoses. The initial results with the value of color Doppler sonography]

Comparative Accuracy of Renal Duplex Sonographic Parameters in the Diagnosis of Renal Artery Stenosis: Paired and Unpaired Analysis

OBJECTIVE

The purpose of this study was to evaluate the test performance of duplex sonographic parameters in screening for hemodynamically significant renal artery stenosis, which occurs in approximately 5% of persons with hypertension.

MATERIALS AND METHODS

A comprehensive literature search was conducted to find studies on the diagnosis of renal artery stenosis in which duplex sonography and intraarterial angiography were compared and in which sensitivity and specificity were calculated. MEDLINE (1966-2005), EMBASE (1988-2005), and reference lists were searched and the authors contacted. Data were subjected to meta-analysis according to the hierarchical summary receiver operating characteristic curve model. Heterogeneity in test performance relating to population and design features was investigated.

RESULTS

From 1,357 titles, 88 studies involving 9,974 arteries in 8,147 patients were included. The following four parameters were evaluated: peak systolic velocity (21 studies), acceleration time (13 studies), acceleration index (13 studies), and renal-aortic ratio (13 studies). The corresponding diagnostic odds ratios (ORs) were 60.9 (95% CI, 28.3-131.2), 28.9 (95% CI, 7.1-117.2), 16.0 (95% CI, 5.1-50.6), and 29.3 (95% CI, 12.7-67.7). Results based on studies in which parameters were directly compared showed that peak systolic velocity had greater accuracy than renal-aortic ratio (relative diagnostic OR, 1.8; p = 0.03; nine studies) and acceleration index (relative diagnostic OR, 5.3; p < 0.001; five studies). Acceleration time versus acceleration index showed no evidence of a difference in accuracy (relative diagnostic OR, 1.1; p = 0.65; nine studies). Analysis of peak systolic velocity used in combination with other parameters compared with peak systolic velocity alone (seven studies) showed evidence of a shift in test positivity (p < 0.001) but only weak evidence of improvement in accuracy (relative diagnostic OR, 1.6; p = 0.09).

CONCLUSION

Sonography is a moderately accurate screening test for renal artery stenosis. The single measurement, peak systolic velocity, has the highest performance characteristics, an expected sensitivity of 85% and specificity of 92%. Additional measurements do not increase accuracy.

Phase-contrast magnetic resonance flow quantification in renal arteries: comparison with 133Xenon washout measurements

To assess the accuracy of 2D phase-contrast magnetic resonance (2D PC MR) renal artery flow measurements, data obtained with this technique were compared with those acquired with the 133Xenon-washout procedure. In addition, the 2D PC MR flow data were related to functional renal information as derived from selective arterial and venous renin sampling. In 53 patients suspected of having renovascular hypertension, MR angiography of the renal arteries was performed, followed by a 3-step angiographic procedure: (1) selective venous and arterial renin sampling; (2) assessment of the renal blood flow by means of the 133Xenon washout technique, and (3) conventional renal angiography. After initial assessment, 71 kidneys were left for analysis. The overall prevalence of renovascular disease > or =50% stenosis was 18%. Mean renal blood flow as assessed with the 2D PC MR technique showed a significant correlation with the 133Xenon washout flow measurements, with a Pearson correlation coefficient of 0.69 (2-tailed; P<0.01). PC MR blood flow measurements correlated poorly with the presence and/or severity of renovascular disease on conventional angiography (r=0.1, P=0.36). Likewise, no statistically significant correlation with either renal venous renin levels or the renin ratio could be identified. Measurement of renal artery blood flow with the use of a 2D PC MR technique is technically feasible. However, the mean renal artery blood flow correlates poorly with either the presence of renovascular disease on angiography or with renin levels. Further improvement of this technique is necessary before it can be applied on a larger scale.

Renovascular disease in patients with hypertension: detection with duplex ultrasound

The aim of this study was to evaluate the accuracy of duplex ultrasound for the diagnosis of renovascular disease in a cohort of hypertensive patients. In 78 patients suspected of renovascular hypertension on clinical grounds duplex ultrasound examination of the renal arteries was performed. Renal angiography was used as the standard of reference. Duplex ultrasound was inconclusive in 11 kidneys (7%). None of the supernumerary renal arteries was detected with duplex ultrasound. The overall prevalence of significant renovascular disease (> or =50% stenosis) was 20%. Based on the combination of parameters at thresholds commonly applied in current literature: ie PSV(max) >180 cm/sec and RAR >3.5 the overall sensitivity of duplex ultrasound for detection of haemodynamically significant renovascular disease was 50.0% with a specificity of 91.3% (PPV: 87.9%; NPV: 59.1). Lowering the thresholds for both parameters improved the test results at the cost of a significant increase of false positive examinations. In a population of hypertensive patients clinically suspected of renovascular hypertension, only limited results for duplex ultrasound could be acquired in the detection of renovascular disease. This result, in combination with the wide range of sensitivities and specificities published in international literature and the relatively large number of incomplete examinations does not support the general application of duplex ultrasound as a screening procedure for detection and assessment of renovascular disease.