hemothorax /hē′mōthôr″aks, hem′-/ [Gk, haima + thorax, chest] , an accumulation of blood and fluid in the pleural cavity, between the parietal and visceral pleura, usually the result of trauma. Blood can also accumulate in the thoracic cavity as a result of erosion of pulmonary vessels, the rupture of blebs, or granulomas. Hemothorax also may be caused by the rupture of small blood vessels in inflammation caused by pneumonia, tuberculosis, or tumors. Shock from hemorrhage, pain, and respiratory failure follow if emergency care is not available. Also spelled haemothorax.