Visualization of the azygos arch valves on multidetector-row computed tomography.

To evaluate the frequency and appearance of the azygos arch valves on chest examinations using multidetector-row computed tomography (MDCT), we retrospectively reviewed findings from 194 contrast-enhanced MDCT examinations of the chest. Rate of injection of 300 mgI/ml contrast materials was low (2.0 ml/s) and high (3.0 ml/s). Scanning delay was 80 s on examination on low-rate injection of contrast material and 20 s on high-rate injection of contrast material. The presence of residual contrast material in the azygos arch valves and reflux of contrast material into the azygos arch were recorded. The Cochran-Armitage trend test was used to compare the frequency of residual contrast material in the azygos arch valves and reflux of contrast material into the azygos arch in both groups. Of 92 examinations of high-rate injection of contrast material, 63 (68.5%) demonstrated residual contrast material in the azygos arch valves and 71 (77.2%) demonstrated reflux of contrast material into the azygos arch. A significantly higher frequency of reflux of contrast material into the azygos arch and residual contrast material in the azygos arch valves was seen in the high-rate injection group than in the low-rate injection group (P < 0.05). Residual contrast material in the azygos arch valves was demonstrated more frequently when contrast material was administered in the right side of the arm than in the left side of the arm (P < 0.05). Reflux of contrast material into the azygos arch was common in the high-injection-rate group and residual contrast material in the azygos arch valves was far more frequently seen in the high-injection-rate group than in the low-injection-rate group on MDCT.