Medical distinction between pulmonary edema and pleural effusion

The common expression ‘water in the lungs’ can refer to two distinct medical conditions: pulmonary edema or pleural effusion. Pulmonary edema involves fluid accumulation within the lung tissue and alveoli, often linked to severe left ventricular heart failure. In contrast, pleural effusion involves fluid buildup in the pleural space surrounding the lungs.

According to a 2023 review in American Family Physician, pleural effusion affects approximately 1.5 million patients annually in the United States. Common causes in adults include heart failure, infections, cancer, and pulmonary embolism. Dr. Alessandro Mariani, a thoracic surgeon at the University of São Paulo, emphasizes that medical treatment depends on whether the fluid is inside or around the lungs and identifying the underlying cause, such as heart, liver, or kidney disease.