Dull percussion most likely indicates which of the following?

• A. Hyperresonance
• B. Hyperinflation
• C. Pneumothorax
• D. Pleural effusion

Answer: (D)

Dull percussion reflects increased density beneath the percussion point, such as fluid or solid tissue. A pleural effusion places fluid in the pleural space, layering at the bases and muffling sound transmission, so the percussion note becomes dull. This finding fits with fluid collection around the lung and is typically accompanied by reduced breath sounds over the affected area.

In contrast, more air in the chest—seen with hyperresonance in pneumothorax or emphysema—produces a louder, booming sound, not dull. Hyperinflation is also associated with increased resonance rather than dullness.

So, dull percussion is most consistent with a pleural effusion.