Teaching Case

A 64-year-old female patient, with the previous history of total splenectomy, total gastrectomy, partial left resection of the diaphragm and additional distal pancreatectomy for diffuse large B-cell lymphoma (DLBCL) presented at the emergency room with left quadrant abdominal pain.
An abdominopelvic computed tomography (CT) examination was performed for further investigation.

An abdominopelvic computed tomography (CT) was performed and revealed a left subdiaphragmatic abscess. A percutaneous image-guided drainage was performed with early clinical improvement.
An upper gastrointestinal (UGI) endoscopy was performed and detected an oesophagojejunal anastomosis leakage, which was managed endoscopically with a covered metal stent.
Two weeks post-admission, the patient developed sudden chest pain, and a chest-CT was requested. It revealed the presence of pneumopericardium, associated with pericardial and bilateral pleural effusion. Ancillary findings such as pericardial fluid high attenuation and enhancing of both layers of the pericardium suggested an inflammatory aetiology.
We hypothesised that pneumopericardium was induced by a fistulous communication between the pericardium and the intra-abdominal abscess, apparently facilitated by prior left diaphragm resection. An iatrogenic aetiology, either during abdominal catheter or metal stent placement could not be excluded.

Pneumopericardium is a relatively rare condition, less common than isolated pneumomediastinum or pneumothorax. It was first described in 1844, and is defined by the presence of an air collection in the pericardial cavity, confined by pericardial reflections [1, 2].
In the adult population, many cases have been reported as a result of blunt or sharp trauma. Other aetiologies include iatrogenic causes related to invasive procedures such as thoracic surgery, thoracocentesis, endotracheal intubation, or positive pressure mechanical ventilation. Non-iatrogenic causes include an underlying infectious process or a fistulous communication between the pericardium and other air-containing structures such as the bronchus, gastrointestinal tract or abscess. There are also reports of spontaneous pneumopericardium in healthy adults [2, 3, 4].
Clinical manifestations are variable and non-specific, and customarily includes chest pain, dyspnoea or palpitations.The symptoms are usually related to the extent of the pneumopericardium and underlying aetiology. In 37% of patients with pneumopericardium, cardiac tamponade may develop, increasing mortality to 58%. It occurs when the amount of pericardial gas is enough to impair right ventricular filling [2, 4].
As so, recognition of its imaging manifestations can be life-saving on a patient with pneumopericardium.
The diagnosis of pneumopericardium is made by conventional chest radiographs or more accurately by chest CT [3].
Chest radiographs depict a continuous thin radiolucent rim of air encompassing the cardiac silhouette and outlined by a fine line, representing the pericardial sac. The main differential diagnosis includes pneumomediastinum. If present, pericardial effusion or thickening may aid in distinguishing these two entities [2, 3, 5].
In pneumomediastinum, gas doesn't surround the heart entirely and isn't confined to the heart region. It is seen as faint streaks of gas extending to the superior mediastinum and neck [2].
Chest CT can efficiently confirm the diagnosis and is the mainstay of diagnosis of pneumopericardium in complex cases, easily demonstrating the heart being partially, or entirely, surrounded by air [3, 5, 6].
The clinical course of pneumopericardium remains highly variable. The volume and speed of the constitution of pneumopericardium are the chief determinants that will conduct, along with the underlying aetiology, the therapeutic strategy. Although it can resolve spontaneously, in the presence of acute cardiac tamponade, an emergent pericardiocentesis is required to immediately restore haemodynamic stability, followed by pericardial fenestration/drainage [3, 5].
For our patient, we hypothesised that pneumopericardium was induced by a fistulous communication between the pericardium and the intra-abdominal abscess. As clinical and ECG findings are nonspecific, recognition of its imaging manifestations can be life saving on a patient with pneumopericardium.