Intrapericardial Cysts in the Dog

Intrapericardial cysts were identified as the cause of impaired cardiac filling in six young dogs. Pneumopericardiography and two-dimensional echocardiography showed the cysts in 2 of 2 dogs and in 4 of 4 dogs, respectively. One dog, which was also infected with heartworms, died before surgical excision of the cyst could be performed. In the remaining dogs, surgical excision of the cysts and subtotal pericardiectomy was successfully accomplished. Histologic examination of the excised tissue from one dog suggested that it was a pericardial coelomic cyst. The gross and histologic characteristics of the cysts removed from the other five dogs resembled those of acquired cystic hematomas. The etiopathogenesis of these cysts was uncertain, but all cysts were connected to a fatty pedicle of tissue. In one dog, a stalk of tissue was observed to enter the pericardium through a small peritoneopericardial diaphragmatic hernia. In four dogs, the stalk of tissue was adhered to the apex of the parietal pericardium. These observations suggested that intrapericardial cysts, in some dogs, develop in association with, and possibly as a result of, congenital herniation and entrapment of omentum or a portion of the falciform ligament into the pericardial sac.