Discordant situs of thoracic and abdominal viscera

Two instances of levocardia with thoracic situs solitus and abdominal situs inversus, and one of their mirror image counterpart are described. No intracardiac defects were present in 2 cases, and the third had a fossa ovalis type of atrial septal defect with partial anomalous pulmonary venous connection. The course of the inferior vena cava was unusual in that the vein switched abruptly from one to the other side of the abdomen at the liver to connect with the venous atrium located on the opposite side. The cases described are thought to represent a specific type of anomaly of visceral situs, characterized by complete thoracic and abdominal discordance. A similar anatomic relationship of the heart and viscera, and course of the inferior vena cava, may occur in more complex types of heterotaxia associated with severe cardiac anomalies, and asplenia or polysplenia. Analysis of these cases reveals that continuity between the inferior vena cava and morphologic right atrium appears to be the most reliable method for atrial localization.