Postmortem imaging identified pneumomediastinum in two cases of diabetic ketoacidosis

Pneumomediastinum is defined as the presence of extraluminal gas within the mediastinum. Hamman described a diabetic ketoacidosis (DKA) patient with subcutaneous emphysema and spontaneous pneumomediastinum, a case known in current times as Hamman's syndrome and now pneumomediastinum is known to be one of the accompanying findings of DKA. We describe two cases with diabetes mellitus in which postmortem computed tomography (CT) could detect pneumomediastinum prior to autopsy. One was a woman in her 40 s, who had type II diabetes mellitus with bronchopneumonia in the middle and lower lobes of the right lung (Case 1) and the other also aged in her 40 s with type I diabetes mellitus (Case 2). In these cases with diabetic mellitus, the finding of pneumomediastinum at postmortem CT gave differential diagnostic considerations of DKA in addition to common cause such as decomposition or cardiopulmonary resuscitation. Autopsy with histopathological and biochemical examination suggested the cause of death in both cases were fatal DKA. The main cause of pneumomediastinum in Case 1 was pulmonary emphysema, and DKA was an exacerbation factor of pneumomediastinum. In contrast, DKA could have caused pneumomediastinum in Case 2, so called Hamman's syndrome. Pneumomediastinum is an obvious morphological abnormality, and thus we should pay attention to the information of pneumomediastinum from postmortem CT scanning.