This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Radiology
Water bottle hea is seen in - 
Select and explain. 
A. PDA, B. Chronic emphysema, C. Pericardial effusion, D. Constrictive pericarditis
C: Pericardial effusion
Answer: C: Pericardial effusion 
Explanation: It refers to the shape of the cardiac silhouette on erect front chest xrays in paients who has a large pericardial effusion. * there can be globular enlargement of the cardiac shadow giving a water bottle configuration * lateral CXR may show a veical opaque line (pericardial fluid) separating a veical lucent line directly behind the sternum (pericardial fat) anteriorly from a similar lucent veical lucent line (epicardial fat) posteriorly; this is known as the Oreo cookie sign 5