In the context of mediastinal emphysema/pneumomediastinum, the main aetiologies are associated with oesophageal perforation, lung pathology or post head and neck surgery related. The main way to differentiate the pathologies would be through Computed Tomographic Imaging of the Thorax and abdomen with oral and intravenous contrast in the context of triple phase imaging. The causes of pneumomediastinum should be differentiated between traumatic and non-traumatic. Oesophageal perforation (Boerhaave syndrome) is associated with Mackler’s triad in upto 50% of patients (severe retrosternal chest pain, pneumomediastinum, mediastinitis). Whereas in cases of lung pathology this can be associated with pneumothorax and pleural effusion.

With much interest the article by Dai et al[1] was read with a greater understanding of mediastinal emphysema in the context of perforated gastric ulcer. In the context of mediastinal emphysema/pneumomediastinum, the main aetiologies are associated with oesophageal perforation, lung pathology or post head and neck surgery related. The main way to differentiate the pathologies would be through Computed Tomographic Imaging of the Thorax and abdomen with oral and intravenous contrast in the context of triple phase imaging[2]. The causes of pneumomediastinum should be differentiated between traumatic and non-traumatic. Oesophageal perforation (Boerhaave syndrome) is associated with Mackler’s triad in upto 50% of patients (severe retrosternal chest pain, pneumomediastinum, mediastinitis)[3]. Whereas in cases of lung pathology this can be associated with pneumothorax and pleural effusion[4].

In this case the context is that of non-traumatic cause, the main aetiology associated with perforation is due to increased intra-oesophageal pressure associated with a closed oesophageal sphincter[5]. The two main concerning features on clinical examination was that of rebound tenderness with abdominal rigidity and that of a low oxygen saturation on pulse oximetry. In the case following a definitive diagnosis of gastric perforation, the patient underwent open repair of the perforation which led to resolution of symptoms.

Pneumomediastinum has also been documented in cases post head and neck surgery usually in association with intermittent positive pressure ventilation. In these cases, patients would likely have marked subcutaneous emphysema as air tracks across the tissue planes and across the compartments. One of the theories that have been postulated to cause this is laryngeal or tracheal tear during placement of endotracheal tubes and subsequently application high positive end expiratory pressure[6,7].

Oesophagogastroduodenoscopy although would potentially allow direct visualisation of the site of perforation, this diagnostic modality is best avoided to limit any further damage from iatrogenic injuries[8]. This would be typically avoided until the perforation has sealed.

From an emergency department perspective- the diagnosis of pneumomediastinum and its likely source are the pertinent factors. Oesophageal perforation if delayed to diagnosis is associated with increased morbidities and increased mortality. Thereby it is pertinent that appropriate investigations are carried out in an expedited manner. The areas of natural weakness in the gastrointestinal tract need to be evaluated for sites of possible perforation. The commonest site for oesophageal perforation is the left postero-lateral aspect of below the diaphragm, however the young it is noted to that the perforation occurs into the right pleural cavity[9]. As reported in previous cases the incidence of both pneumomediastinum and pneumothorax is rare is context of visceral perforation. One of the main theories to explain this mechanism is that intra-peritoneal air diffuses through the peritoneal membrane reaching the pleural cavity other theories include passage of air through the diaphragmatic fenestrations and the final mechanism is the passage of retroperitoneal air that passes into mediastinal cavity[10,11].

In terms of diagnosis of perforated gastric ulcer, the main imaging modality would a standard porto-venous computed tomography (CT) imaging of the abdomen and pelvis. The standard protocol would include the part of the lung bases, thereby would still be able to detect the presence of bilateral pleural effusion, pneumomediastinum and pneumothorax. If this would be detected then a follow up CT imaging of the thorax and abdomen with oral contrast would be able to differentiate the cause of the pneumomediastinum. In terms of surgical management perforated peptic ulcer would be operated by the general oncall surgical team with the commonest procedure being either laparoscopic with laparotomy (if gross contamination is present) with omental patch repair[12]. However. If the diagnosis is Boerhaave’s syndrome then the input of the upper gastrointestinal surgeons would be needed. This can be logistical challenge especially when not all surgical sub-specialities are at the same facility.

As highlighted in this editorial, the attending clinician needs a high index of suspicion when considering the various causes of pneumomediastinum in the context of a surgical abdomen.

I would like to congratulate the authors in the publication of their article.