Haemopericardium pericardial fluid collection composed of blood. Haemopericardium to some extent occurs after cardiac surgery. It may also be caused by blunt or penetrating trauma, perforation of the heart or a coronary artery after cardiac catheterization and coronary angioplasty respectively. Haemopericardium may also occur with some pericardial metastatic tumours and with the postpericardiotomy syndrome. Postoperative haemopericardium is now recognized as an aetiological factor for the development of constrictive pericarditis. Chest X-ray demonstrates widening of the cardiac silhouette as with any pericardial effusion. The diagnosis of haemopericardium can be made with spin echo MRI. On T1-weighted images, haemopericardium has high signal intensity of part of nearly all of the effusion as opposed to the low intensity of nonhaemorrhagic effusion may disclose high density of a pericardial haematoma.