A case of hemothorax following seat-belt injury with a bulla in the apex of the lung: a subtype of spontaneous hemopneumothorax.

We experienced a case of a subtype of spontaneous hemopneumothorax caused by external forces associated with a seat-belt injury. A female aged 39 years sustained a minor collision with an oncoming car while she was driving. Although pneumothorax was not detected, hemothorax and bleeding from the area surrounding the subclavian artery were observed on contrast-enhanced chest computed tomography (CT). After confirming continuous bleeding into the thoracic cavity after superselective arterial embolization, we performed emergency open surgery. We found a bulla in the apex of the lung, and the thoracic stump of the bulla was considered the source of bleeding. In this case, the direct cause of hemothorax was considered to be the external force associated with the seat-belt injury. When a bulla in the apex of the lung and continuous bleeding are both observed on CT, spontaneous hemopneumothorax should be suspected, necessitating open chest surgery in cases where pneumothorax is not observed.