Background Atraumatic hemothorax presents a diagnostic challenge due to its rarity and the wide, diverse range of potential etiologies. We present a case of massive hemothorax without a clear cause, aiming to highlight the complexities of this pathology and the critical considerations necessary for accurate diagnosis.

Case Presentation A 20-year-old male with a history of spine surgery presented to the ED following two syncopal episodes and a one-day history of nausea, vomiting, and right-sided back pain. The patient began practicing Jiujitsu two days prior but denies any significant injuries. Upon EMS arrival, systolic blood pressure was 90 mm Hg and the patient remained hypotensive after receiving two units of crystalloids. Chest X-ray revealed a large right-sided pleural effusion and thoracentesis with subsequent tube thoracostomy evacuated three liters of blood. The patient was transferred for higher level of care, and was transfused with four units of packed red blood cells, one unit of fresh frozen plasma, and a bolus of tranexamic acid. A FAST exam was negative. An additional 700-800 mL of sanguineous blood was evacuated upon a second thoracostomy with chest tubes left in place. CT angiography of the chest, abdomen, and chest did not reveal active contrast extravasation or traumatic injury of the aorta. Over the following five days, the patient’s symptoms and hemothorax resolved, chest tubes were removed, and the patient was discharged. There are no records of patient readmission.

Discussion Massive hemothoraces, defined by blood drainage exceeding 1,000 mL after closed thoracostomy, are typically associated with high-impact traumas such as blunt or penetrating chest injuries. We present an unusual case with minimal evident trauma. Although our patient denied significant injury, it is possible that a minor incident may have been overlooked. We suspect our patient’s hemothorax was due to intercostal artery damage if he did suffer some type of injury. Regardless, minor injury alone would still not typically explain this massive hemothorax and therefore, must also consider the possibility of a massive, non-traumatic hemothorax due to coagulopathy, vascular malformations, connective tissue diseases, or autoimmune diseases. Given the unclear history, a broad differential diagnosis is crucial. This case underscores the importance of gathering a detailed history during the patient encounter and maintaining a high degree of suspicion for hemothorax in cases of refractory hypotension, even in the absence of a clear trauma history.