Byoung Chul Cho, et al. lation of chyle in the pericardium associated with mediastinal cystic hygroma. They used the term “primary idiopathic chylopericardium” in this first case report because no apparent etiologic mechanism was evident. This is such a rare condi- tion that a computerized Medline search from 1960 to 2003 identified fewer than 35 cases of primary idiopathic chylopericardium, including our case. Its etiology is obscure, though in recent years, a few reports have described a lymphatic leak and fistula by combined lymphangiography and computed tomography or intraoperative thoracic ductogram.9,14 These reports clearly dem- onstrate a leaking flow of contrast media from the thoracic duct to the pericardial sac. This disorder has two possible explanations: (1) the presence of damaged lymphatic valves and the communica- tion of thoracic duct to the pericardial lymphatics resulting in chylous reflux and (2) abnormally elevated pressure in the thoracic duct observed as lymphangiectasia.14,15 Diagnostic modalities essential for evaluating suspected chylopericardium include the follow- ing: A chest X-ray demonstrating cardiomegaly will lead to further investigations and eventually diagnosis. Pericardial effusion is usually diag- nosed by echocardiography or computed tomo- graphy. The nature of the effusion is usually revealed by pericardiocentesis.9 Computed tomo- graphy and lymphangiography may be useful in the diagnosis of mediastinal lymphangiomatosis, which is the most common cause of primary chylopericardium.17 Investigation specifically tar- geting malignant disease, lymphoma and tuber- culosis should also be undertaken.2,4 A history of trauma caused by thoracic surgery,6,7 the intro- duction of a subclavian venous catheter,3 or blunt trauma5 should be determined. Lymphangiogra- phy may in certain instances establish fistulous connections and is also useful for delineating the anatomy of the thoracic duct.9,14,21 Primary chylo- pericardium should be considered in the differ- ential diagnosis of chronic pericardial effusion. As is pointed out in a review by Akamatsu,14 about a half of patients are asymptomatic or were noted to have only cardiomegaly by chest X-ray. Cystic hygromas (lymphangiomas) may arise from lymphatic tissue normally present in the area or may grow directly from mesodermal rests that Yonsei Med J Vol. 46, No. 3, 2005 produce imperfect lymphoid channels.18 These lesions are usually found in the neck or axilla. It is apparent that lymphangioma may be multi- focal, involving mediastinum, retroperitoneum, and even the skeletal system, and that they produce a number of apparently separate syn- dromes depending on the anatomic location of the lesion.18-20 Our patient had cystic lesion in the neck, but she refused biopsy for a definitive diagnosis. However, according to the smoothly marginated cystic mass on CT scan and the compressibility of the lesion by sonography, we concluded that this cystic lesion was a cystic hygroma. In our case, we failed to visualize any communication between the thoracic duct and the pericardial sac by lymphangiography and com- puted tomography of the chest. Tucker et al.20 in 1967 reported idiopathic chylothorax in asso- ciation with a cystic lesion of the bone, and Goldstein et al.18 in 1969 reported an association of a chylopericardium with multiple lymphan- gioma of the bone. Moreover, although they failed to demonstrate a clear communication between the pericardial space and the thoracic duct, they pointed out a generalized abnormality of the lymphatic system in patients with lym- phangiomas. We strongly believe that a cystic hygroma of the neck and chylopericardium reflect a generalized disorder of the lymphatic system in our patient. An abnormal lymphatic system may cause the lymphatic channel pressure elevation and increase the permeability of lymphatic ves- sels, resulting in the reflux of chyle through certain communications between the lymphatic system and the pericardial sac.18-20 The management of chylopericardium is guided by the prevention of cardiac tamponade, and the avoidance of the metabolic, nutritional, and immunologic consequences that occur given a significant chyle leak, and to reduce the like- lihood of recurrence.8-16 Several different ap- proaches make be adopted for the treatment of chylopericardium: (1) pericardiocentesis, (2) tho- racostomy drainage, (3) dietary support with medium or short chain triglyceride and low fat meals, (4) pericardiectomy, (5) pericardial win- dow formation, (6) ligation of the thoracic duct above the level of the diaphragm, and (7) a pericardial-peritoneal (Denver) shunt. In contrast