Contrast-related flow phenomena mimicking pathology on thoracic computed tomography

Flow phenomena occurring after the bolus injection of contrast material can simulate the presence of pathology on thoracic computed tomography. In a review of 50 dynamic scans performed after contrast medium injection, apparent filling defects in the superior vena cava were seen in 46. In four cases, retrograde filling of the azygos or hemiazygos veins occurred. In two cases, layering of contrast material within the descending aorta simulated dissection. In many cases, the dynamic series of scans helped in diagnosing these appearances as flow related.