Invisible pulmonary markings due to air in the pulmonary vasculature: a post-mortem study

Pulmonary vascular markings were invisible on a postmortem chest radiograph because of air in the pulmonary vessels in a patient who had exsanguinated. This unusual case illustrates that it is the blood in the pulmonary arteries and veins, rather than the vessels' walls, that accounts for the normal lung markings on the plain chest radiograph.