Case summary

A 40-year-old male came to emergency with history of Motor Vehicle Accident. On examination he was found to have multiple palpable rib fractures and subcutaneous emphysema bilaterally. He had cranio-cerebral trauma also (Glasgow Coma Scale 4/15). Bilateral intercostal tubes were inserted and tracheostomy was done after stabilizing the cervical spine. Fluid resuscitation continued. On secondary survey, the abdomen was soft but 3 hours later, subcutaneous emphysema was present reaching down to the umbilicus. Meanwhile, cervical spine X-ray showed cervical spine subluxation at the level of C3-4 and chest and abdominal X-ray revealed air under the diaphragm on both sides (fig. 1). Ultrasonography could not contribute much due to subcutaneous emphysema. Other investigations like CT scan could not be done due to poor general condition. Since vitals were not getting stabilized despite best resuscitation, it was decided to explore the abdomen in view of air under the diaphragm. On exploration, to our great surprise none of the hollow viscera was found perforated and the abdomen was practically virgin. The abdomen was closed after putting a drain in the pelvis.

Figure 1

Fig.1: X- ray showing huge amounts of air under the diaphragm on both sides

Discussion

Pneumoperitoneum means air beneath the diaphragm, i.e. in the abdominal cavity, and is a radiological term¹. It is commonly the result of visceral perforation. Uncommonly, some non-surgical causes of pneumoperitoneum can be seen. Presence of air under the diaphragm warrants surgery to prevent morbidity and mortality. Causes of pneumoperitoneum without visceral perforation include intra-thoracic or gynecologic ones, or it may also be iatrogenic (like post-operative and post-ERCP pneumoperitoneum); these forms are usually managed conservatively.^2,3

Pneumoperitoneum is the result of a gastrointestinal (GI) tract perforation in more than 90% of cases². Other causes include trauma (including barotrauma), pneumothorax and bronchoperitoneal fistula, emphysematous cholecystitis, spontaneous bacterial peritonitis, ruptured hepatic abscess and perforated pyometra, mechanical ventilation and after sexual voilence.⁴ Perforation of the stomach or duodenum caused by peptic ulcer is considered the most common cause of pneumoperitoneum. Pneumoperitoneum can also be the result of a diverticular rupture or of an abdominal trauma³.

Entry of air through thorax into the abdomen has been explained through microscopic defects present in pleura and diaphragm. Air can even enter through the mediastinum along perivascular connective tissue traveling retroperitoneally and then rupturing into the peritoneal cavity causing pneumoperitoneum. Even cardiopulmonary resuscitation can lead to abdominal free air due to combination of increased airway pressure and application or blunt force to the chest.⁵

In the present case, the patient had sustained various systematic injuries along with thoracic trauma signifying major impact at the time of accident. The best method is serial monitoring of X-ray or serial CT showing increasing or decreasing air. In the present case, the general condition of the patient did not allow serial radiologic monitoring. There is paucity of similar experience in literature. ^6-9

Despite demonstration of air under the diaphragm in X-ray, one may rarely not find any obvious cause; yet exploration in such a case is not totally out of place for obvious reasons.