Pericardial effusion is defined as which of the following?

• A. Buildup of fluid between the visceral and parietal pericardium
• B. Thickening of the pericardium
• C. Blood pooling in the pericardial space
• D. Fluid in the pleural cavity

Answer: (A)

Pericardial effusion is the buildup of fluid in the pericardial cavity, the space between the visceral and parietal layers of the pericardium. Normally this space contains only a small amount of lubricating fluid; when fluid accumulates, the sac enlarges and can compress the heart, potentially impairing filling and, if large or rapid, causing tamponade. This is distinct from thickening of the pericardium, which is a structural change rather than fluid collection. A collection of blood in the pericardial space is hemopericardium, a different scenario often related to trauma. Fluid in the pleural cavity refers to a pleural effusion, which involves the space around the lungs, not the pericardial sac.