Hemiazygos vein as a cause of posterior indentation of the esophagus: a case report.

The hemiazygos vein crosses the midline at the level of D8 between the esophagus and spine to join the azygos vein. Any condition causing dilatation, from either obstruction or collateralization, can dilate the hemiazygos vein and produce posterior indentation of the esophagus. This vein is collapsible so it can easily be wedged between the esophagus and thoracic spine. Although various causes of indentations on the posterior wall of the esophagus have been described, we are not aware of any previous report of an esophageal impression from a dilated hemiazygos vein and therefore report such a case.