by Dr Noreen Norfaraheen Lee Abdullah MD (UKM), MMed Radiology (UKM), AM(Mal)

Answer to Case Of the Month 
Pulmonary Interstitial Emphysema complicated by pneumomediastinum and pneumoperitoneum

Discussion of Findings
There is bilateral symmetrical hyperinflation. In the lung fields, multiple tortuous linear and cystic lesions are seen radiating from the hilar regions intermixed with patchy alveolar opacities. These lesions extend to the lung periphery. These features are compatible with pulmonary interstitial emphysema.

A chest tube is seen in the right hemithorax. There is now no evidence of a pneumothorax. The endotracheal tube is in a good position, at the level of T2 (but this is difficult to appreciate in the radiograph here). There is pneumomediastinum.

In the abdomen, the football sign is positive. It denotes the presence of a large pneumoperitoneum which outlined the entire abdomen cavity clearly defining the liver, spleen and bowel loops.

PIE occurs when the alveoli or terminal airway ruptures and air escapes into the pulmonary interstitium. Air dissects along the bronchovascular sheaths surrounding the arteries, veins and lymphatics and tracks to the outer periphery of the lung. The air can pass directly into the mediastinum or burst through the visceral pleura into the pleural space. In the first case it is known as pneumomediastinum while in the latter it is known as pneumothorax. Mediastinal air can track into the soft tissues of the neck. It can also track through the retrosternal transdiaphragmatic communications into the peritoneal cavity resulting in pneumoperitoneum.

Several reasons are available to explain this sequence of events:

1. infant’s own forceful respiratory efforts

2. positive pressure assisted ventilation

3. resuscitative measures

4. widespread or focal air trapping causing air block

In all cases, there is a continual supply of air which is under pressure and serves as meandering conduits along the bronchovascular sheaths making it continuously filled with air. It is a serious problem as the lung becomes severely splinted and does not fill or empty with respiration. This means there is no ventilation or gas exchange occurring.

Radiographically the findings are hyperinflation. There are multiple elongated lucencies radiating from the hilum and gives a bubbly lung field appearance. The lucencies extend to the periphery of the lung and do not change with respiration. Occasionally there is lobar overdistension which may lead to complications such as pneumothorax. Other complications that are likely include pneumomediastinum, pneumopericardium, intracardiac air, pneumoperitoneum, pneumatosis intestinalis and subcutaneous emphysema.
 

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Last Updated:
Tuesday, 04 January 2005