Diagnosis of empyema is suggested by which finding?

• A. Sputum culture positive
• B. Clear pleural fluid with low protein
• C. Thoracentesis showing frank pus or cloudy pleural fluid
• D. Normal pleural fluid glucose

Answer: (C)

Empyema is infection of the pleural space with accumulation of purulent fluid. The most definitive clue is the gross appearance of the pleural fluid obtained by thoracentesis: frank pus or a clearly cloudy, pus-containing effusion confirms empyema.

Sputum culture being positive indicates a lung infection but does not prove pleural space infection. A pleural effusion that is clear with low protein points to a nonpurulent transudate or uncomplicated exudate, not empyema. Normal pleural fluid glucose is not typical in empyema; the glucose in pleural fluid is often low due to consumption by bacteria and inflammatory cells.