Pneumomediastinum due to Macklin effect

Case contributed by Stefan Tigges

Presentation

HIV+, shortness of breath.

Patient Data

Age: 40 years
Gender: Male

Standard & Edge Enhanced pCXR

x_ray

Pneumomediastinum with air to the left of the descending aorta and along the left heart border extending into the neck.

Fluoroscopy

Contrast swallow shows no esophageal contrast extravasation.

Diffuse ground-glass opacity and scattered cysts are compatible with PJP pneumonia. Bilateral lower lobe pulmonary emboli and bilateral lower lobe consolidation may represent hemorrhage or infarct. Pulmonary interstitial emphysema (see annotated images below) left upper lobe tracking back to the mediastinum likely accounts for the pneumomediastinum. No tracheobronchial tree injury.  No pneumothorax.

Annotated image

Interstitial air labeled on axial and coronal lung windows.

Case Discussion

Although esophageal/tracheobronchial tree injury must be considered in patients who present with pneumomediastinum, the etiology is often an overdistended alveolus that ruptures, with air tracking back to the mediastinum along bronchovascular bundles. Pneumothorax often accompanies pneumomediastinum: additional overdistended subpleural alveoli may rupture into the pleural space.

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