The document summarizes pericardial diseases. It discusses the anatomy and physiology of the pericardium, acute pericarditis including symptoms, diagnosis and treatment, and pericardial effusion and tamponade. Acute pericarditis is usually self-limited and treated with NSAIDs. Larger effusions may require hospitalization. Pericardial effusion can progress to tamponade, where fluid accumulation compresses the heart and impairs filling.