Echocardiographic simulation of pericardial fluid accumulation by right pleural effusion

On two-dimensional echocardiography, in the subcostal four-chamber view, right pleural effusion can present as a large echo-free space adjacent to the echo-free space representing the right atrium, thus simulating a loculated pericardial effusion or a pericardial cyst. On occasion, the echo-free space representing the right pleural effusion can bulge into the right atrium, distorting the right atrial shape, and thereby produce an echocardiographic appearance that may be confused with an indentation of the right atrial wall by pericardial effusion. The latter has recently been described as a sign of pericardial tamponade.