Primary chylopericardium.

Pericardial fluid is created from an epicardial and parietal pericardial capillary ultrafiltrate with contributions from myocardial interstitial liquid that crosses the epicardium [1]. Drainage of pericardial fluid occurs largely through a complex network of lymphatic vessels [2]. Thus, the network of lymphatic vessels is also important for pericardial fluid accumulation.

Chylopericardium is an accumulation of chylous fluid in the pericardial cavity. It occurs generally after chest trauma (blunt or penetrating), or thoracic and cardiac surgery. Episodes of vomiting or violent coughing, which may be related to blunt trauma, can induce chylopericardium. It may also occur as a result of mediastinal neoplasms, mediastinal tuberculosis, mediastinal radiotherapy, filariasis, thrombosis of the subclavian vein, or congenital lymphangiectasis 3, 4, 5, 6, 7.

Primary or idiopathic chylopericardium is a diagnosis in the absence of any apparent precipitating factor. Idiopathic chylopericardium was first reported in 1888 by Hasebrock [8]. The term primary isolated chylopericardium was first reported by Groves and Effler in 1954 [9]. Since then, around 120 cases have been reported from all around the world. It occurs in all ages and affects both sexes equally, although most cases present in children and young adults [10].

Hattori et al. [11] reported two young female cases of chylopericardium with primary chylopericardium, and both cases were asymptomatic. Although the majority of cases are asymptomatic, clinical manifestations may vary; dyspnea, fatigue and cough are common, while tamponade is rare 10, 12.

Chylopericardium is usually diagnosed by pericardiocentesis showing the presence of chylous fluid with high triglyceride level, as Hattori et al. [11] showed.

Primary chylopericardium results from retrograde flow through abnormal lymphatics into a rich pericardial plexus. Although the underlying pathophysiology of primary chylopericardium remains unknown, several mechanisms have been proposed to explain the development of chylopericardium, including: obstruction of the thoracic duct; failure to establish collateral drainage to the right thoracic duct; reflux of chylous lymph through normal lymphatic channels that drain the pericardium and heart; and abnormal connections between the thoracic and pericardial lymphatics.

Because normal lymphatic valves prevent chylous reflux into the pericardial plexus, blunt chest trauma may also induce chylopericardium by inducing an elevated intrathoracic pressure that ruptures lymphatic valves [13]. Moreover, lymphatic hypertension and increased permeability of lymphatics may be alternative mechanisms that could explain the pathogenesis of chylopericardium [14].

Many diagnostic modalities have been described: observation of Sudan III dye distribution into the pericardial cavity after oral intake of Sudan III dye; lymphangioscintigraphy; lymphangiography; computed tomography lymphangiography; and evaluation of chest radioactivity after oral administration of 131I-triolein or 123I-beta-methyl iodophenyl pentadecanoic acid (123I-BMIPP, i.e., lymphoscintigraphy) 15, 16, 17.

Lymphoscintigraphy is faster and less invasive than lymphangiography. Hattori et al. [11] performed 123I-BMIPP lymphoscintigraphy in two cases for diagnosis, and it was useful for detecting abnormal accumulation in both cases before the operation. Thus, lymphoscintigraphy seems to be one of the convenient examinations for the diagnosis of chylopericardium.

Lymphangiography may establish fistulous connections and is also useful for delineating the anatomy of the thoracic duct 18, 19, 20. Previous reports actually demonstrated that lymphangiography combined with computed tomography or intraoperative thoracic ductography identified the locations of the lymphatic leaks and fistulas 18, 19, 20.

Hattori et al. [11] also performed intraoperative thoracic duct angiography to identify the thoracic duct and confirm abnormal communication between the thoracic duct and pericardium with or without thoracic duct obstruction. Drainage and dietary manipulation is an effective therapy in approximately 55% of cases [12]. Surgical treatment is required when failure to respond to a diet rich in medium-chain triglycerides and pericardiocentesis occurs. Information provided by lymphangiography is important for surgery.

Surgical treatment consists of ligation and excision of the thoracic duct and partial pericardiectomy. Thoracic duct ligation has to be performed just above the diaphragm because the anatomy of the thoracic duct may vary, and in approximately 25% of cases, multiple ducts are present at the level above the diaphragm [18]. Pericardiectomy is performed to ensure complete drainage and to prevent later constrictive pericarditis. This procedure has also been performed by video-assisted thoracoscopy (VATS) 21, 22, 23. Hattori et al. [11] treated one patient with primary chylopericardium with VATS. They performed ligation of the thoracic duct, and a partial pericardiectomy successfully in a patient with thoracotomy because they were unable to identify thoracic duct by VATS.

The type of surgical procedure used, VATS versus open thoracotomy, should be decided on a patient-to-patient basis and should be chosen according to each situation by responsible surgeons. Percutaneous catheterization and embolization of the thoracic duct have been reported for treatment of chylothorax and chylopericardium [24]. Further trials are needed to elucidate the effectiveness of this therapy.