Idiopathic right atrial enlargement.

A 26-year-old man presented with lower extremity edema and abdominal protrusion associated with dyspnea for 5 years, which had increased 7 months earlier. Echocardiography demonstrated a huge right atrium of 19.5 × 15.2 cm with a thick smoke pattern and severe tricuspid regurgitation. Magnetic resonance imaging confirmed intact pericardium. A pulmonary perfusion scan demonstrated multiple perfusion defects, suggesting recurrent small pulmonary emboli. Idiopathic enlargement of the right atrium was diagnosed. The patient declined surgery.