Bilateral pneumothoraces, pneumomediastinum and subcutaneous emphysema following spontaneous pneumomediastinum

Clinical History

A 47-year-old woman admitted with sudden onset of shortness of breath, multiple body compartment swelling (orbital, thoracic and abdominal swelling) without history of forceful vomiting. On examination, subcutaneous emphysema was noted in orbit, thorax, both arms and abdomen. There was decreased air entry with hyper-resonant percussion bilaterally. She suffered from peripheral vascular disease, COPD, peripheral neuropathy. She was a heavy smoker and alcohol dependent.

Imaging Findings

After admission chest radiograph was performed and showed extensive subcutaneous emphysema [Fig 1]. CT of the thorax that followed [Fig.2] showed extensive mediastinal emphysema tracking into the neck and retroperitoneum with moderate right and mild left pneumothoraces. There was also consolidation of the left lung basae. Chest drain was inserted in the right side to release the pneumothorax. On the same day, water soluble contrast agent swallow [Fig. 3] showed free flow of contrast agent with no evidence of oesophageal leak.
A series of chest radiographs was performed later and the patient made a good recovery. One week after admission he was discharged safely from the hospital being adviced to stop smoking and reduce alcohol consumtion.

Discussion

Air within the mediastinum can originate from five sites: the lung, the mediastinal airways, the oesophagus, the neck and the abdominal cavity [1]. This can be categorised as spontaneous or traumatic. Spontaneous pneumomediastinum, described for the first time in 1939 by Louis Hamman, is usually seen in young, tall and thin men and unusually in women (as in this case), which is caused by rupture of peripheral pulmonary alveoli due to sudden increase in the intraalveolar pressure after exaggerated Valsalva maneuvers. Traumatic causes could be iatrogenic like barotrauma during mechanical ventilation or due to penetrating or blunt trauma to the chest. Also, it could occur as a complication of obstructive airway processes like foreign body inhalation or asthma [2]. Pneumomediastinum is usually a benign and self-limited condition, but is sometimes dangerous if the mediastinal pressure rises abruptly or decompression does not occur in the subcutaneous tissues. Life threatening complications are possible and include:
1/ Pneumothorax
2/ Tension pneumomediastinum leading to cardiac tamponade
3/ Impedance of pulmonary vascular flow by air within the vascular sheaths.
Pneumomediastinum is diagnosed clinically, the clinical diagnosis being based on the triad of symptoms of chest pain, dyspnoea and subcutaneous emphysema. The standard posteroanterior and lateral radiographs are usually sufficient for diagnosis, as posteroanterior chest radiograph typically demonstrates a radiolucent line between the mediastinal pleura and the left heart border. In the lateral view, air is visualised in the retrosternal space or as lucent streaks outlining the aorta and other mediastinal structures. Posteroanterior chest radiographs may be false positive in 50% of cases, and therefore lateral chest radiograph should always be performed increasing the sensitivity to nearly 100% [3].
Other diagnostic procedures like oesophagoscopy, oesophagogram (with water-soluble contrast agent), bronchoscopy or chest CT are often performed following conventional radiographic imaging to rule out spontaneous or traumatic rupture of oesophagus and tracheobronchial tree or other secondary causes of pneumomediastinum.
Spontaneous pneumomediastinum is a self-limited condition and has a relatively benign clinical behaviour and air in the mediastinum is usually absorbed spontaneously within 2 to 4 days. Therefore conservative management with bed rest and analgesics is the first choice of treatment in most cases. Treatment with oxygen facilitates air absorption in the mediastinum in a similar way as in the spontaneous pneumothorax and is therefore recommended [4]. Decompression of mediastinal air is used in critically ill patients.

Differential Diagnosis List

Final Diagnosis

Bilateral pneumothoraces, pneumomediastinum and subcutaneous emphysema following spontaneous pneumomediastinum

URL:	https://www.eurorad.org/case/9445
DOI:	10.1594/EURORAD/CASE.9445
ISSN:	1563-4086