The presence of effused chyle in the pericardium. In case of conspicuous effusion (> 1500 ml) or of its rapid development (> 200 ml), a heart tamponade may occur, thus requiring immediate drainage. In the majority of cases, a fistular link can be observed between mediastinal lymphatic structures (thoracic duct) and the pericardium. More often, this occurs because of lymphangiodysplasia or after a trauma (even a iatrogenic one).