Partial pericardial defect associated with ruptured aortic dissection of the ascending aorta: a rare feature presenting severe left hemothorax without cardiac tamponade.

We report a very rare case of acute aortic dissection of the ascending aorta, which ruptured to the left pleural cavity through the left-side congenital pericardial defect. A preoperative computed tomographic scan and a roentgenogram showed localized dissection of the ascending aorta and severely deteriorating left hemothorax, which required emergency operation. Intraoperative findings revealed the ruptured aortic dissection of the ascending aorta and the defect at the left-side pericardium, and a graft replacement of the ascending aorta was performed. It was considered that congenital pericardial defect complicates the diagnosis in a case of catastrophic intrapericardial hemorrhage.