Pneumomediastinum: a diagnostic problem.

Pneumomediastinum has numerous etiologies and its pathways of spread are multiple and well defined. Knowledge of these anatomic pathways and possible etiologies is important in order to avoid extensive and unnecessary evaluations. For example, if there is a known reason for pneumomediastinum, and pneumoperitoneum is present without associated abdominal findings, further evaluation for perforated viscus is unnecessary. In a patient who is an asthmatic or a diabetic, the presence of pneumomediastinum should not lead to work-up with contrast studies unless there are specific clinical reasons to do so. In critically ill infants and adults, pulmonary interstitial emphysema is an important warning sign for impending pneumothorax or pneumomediastinum and the patient's physicians should be alerted. There are occasional difficulties in differentiating pneumomediastinum from pneumopericardium and from a medial pneumothorax. Analysis of anatomic details and decubitus views are helpful in this regard.