- due to persistence of blind ending ventral parietal pericardial recesses
- cyst that communicates with pericardial space – pericardial diverticula
imaging
- well defined
- oval or occasionally lobulated
- right cardiophrenic angle (70%)
- left cardiophrenic angle (20%)
- sometimes higher up in mediastinum
- clear fluid
- MR: low to intermediate on T1, high on T2 with no post Gado enhancement