CORRECT!
The differential diagnosis for the causes of an enlarged heart shadow includes cardiomyopathy, aortic stenosis, aortic regurgitation, hypertension, ventricular aneurysm and pericardial effusion. In this patient, the cardiac silhouette is enlarged and has a "flask" shaped or "water bottle" shaped heart. These findings are consistent with a pericardial effusion.
In addition, on the lateral view there is a widened soft tissue density around the heart consistent with a pericardial effusion (arrows). If fluid within the pericardial sac accumulates rapidly, even 100 to 200 ml can cause tamponade. Gradual effusions may develop without any signs or symptoms because the pericardium has time to expand. The diagnosis of pericardial effusion can be confirmed by echocardiography or CT. There are many causes of pericardial effusions including uremia, malignancy, infection and connective tissue disease such as lupus.