A 40-year-old man was admitted with sudden onset of dyspnoea. A few minutes after admission he suffered a respiratory arrest and underwent endotracheal intubation. He had a history of recent upper airway infection but no other traumatic events. The chest radiograph showed a circular air density mass in the mediastinum (fig 1A). A CT scan showed the stomach to be within the posterior mediastinum with compression of the left main stem bronchus (fig 1B). Urgent laparotomy was performed and a gastric herniation at the site of the foramen of Bochdalek was found. The stomach was reduced and the defect in the diaphragm was repaired. The postoperative course was uneventful.

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Figure 1 (A) Chest radiograph showing a circular air density mass in the mediastinum. (B) CT scan showing the stomach within the posterior mediastinum and compression of the left main stem bronchus.

Abdominal viscera can herniate through defects in the diaphragm and produce different types of diaphragmatic hernia. The majority of diaphragmatic hernias in adults are either standard hiatal hernias or those presenting acutely due to traumatic disruption of the diaphragm. The remaining small fraction represent unusual cases such as congenital hernias (Morgagni or Bochdalek) which present in adulthood or traumatic hernias which present months to years after the traumatic (or surgical) event.1 Larger hernias should be operated on because of potential complications which are often fatal.