Surgery General 4f1751eb Most reliable sign of injury to intrathoracic aoa is A Presence of apical cap of pleural fluid B Depression of left main stem bronchous C Obliteration of aoic knob contour D Funny looking mediastenum High-Yield Explanation Answer- C. Obliteration of aoic knob contourThe most reliable of these signs for the blunt aoic iniury is loss ofthe aoic knob contour.