What is the cause of spontaneously resolving pericardial effusion?

Q: A 30 year old man, presented with history of fever of 1 month duration and massive pericardial effusion on X-ray chest. There was no sign of cardiac tamponade. Repeat CXR after 3 days showed almost complete clearance of the pericardial effusion without any specific treatment. What is the most likely diagnosis? What is the mechanism of spontaneous clearance of pericardial effusion?

A:Pericardial effusion that resolves spontaneously is generally viralpericarditis; this a fairly common cause for pericardial effusion. Theonly unusual feature in your case is that the effusion, as youdescribe, was massive. It is therefore advisable for you to repeatan echocardiographic examination at 4wks and 3 months to exclude arecurrence, although this possibility is remote.