Pericaardium is the sac containing heart while peritonium is the membrane that forms lining of the abdominal cavity. Peritoneopericardial Diaphragmatic Hernia (PPDH) is a congenital disorder of dogs and is characterized by displacement of abdomina viscera into the pericardial sac. The degree of herniation is variable and the clinical signs will vary consequently. This disorder is characterized by incomplete formation of the septum transversum during early embryonic development, meaning that the peritoneal cavity and pericardial sac remain continuous in later life. The defect may also result from a failure of the septum transversum to fuse with the pleuroperitoneal folds. Since the diaphragm (which is formed by the septum transversum) does not separate the two cavities, abdominal organs are able to move into the pericardial sac. Liver is most commonly herniated, followed by small intestine, spleen and stomach.
Many dogs do not show any symptoms of this disorder and it is usually an accidental finding such as during neutering or spying. Common symptoms associated with this condition include