Fig. 24

Oreo cookie sign. On lateral chest radiograph the Oreo cookie sign is depicted: it consists of an increased radiopacity of the pericardium (black asterisk)—caused by pericardial effusion—which appears to be anteriorly and posteriorly delimited by two radiolucent lines (black arrows), caused by pericardial and epicardial fat. This radiographic pattern reproduces the so called “Oreo cookie sign,” similar to the famous biscuit