Message in a bottle. The use of chest radiography for diagnosis of pericardial effusion.

Introduction: The diagnosis of pericardial effusion may be elusive, and only diagnosed with echocardiography.

Case reports: Here we report the cases of two patients who presented to the emergency centre (EC) with dyspnoea, and their chest X-rays (CXR) revealed the "water bottle sign", which is the typical appearance of the cardiac silhouette that is present when there is a large pericardial effusion.

Discussion: This clinched the diagnosis of pericardial effusion, where the diagnosis may have otherwise been delayed. We discuss these cases, and the relevant literature and discuss the benefits of standard chest radiography in aiding in the diagnosis of pericardial effusion.