Distinguish transudate from exudate in abdominal effusion by protein concentration and cell count.

• A. Transudate: high protein (>3 g/dL) and high cellularity; Exudate: low protein (<3 g/dL) and low cellularity
• B. Transudate: low protein (<3 g/dL) and high cellularity; Exudate: high protein (>3 g/dL) and low cellularity
• C. Transudate: low protein (<3 g/dL) and low cellularity; Exudate: high protein (>3 g/dL) and high cellularity
• D. Transudate: low protein and low cellularity; Exudate: high protein and low cellularity

Answer: (C)

The important idea is that the nature of an effusion reflects the underlying process: non-inflammatory fluid (transudate) leaks due to pressure or oncotic imbalances, so it carries little protein and few cells; inflammatory fluid (exudate) leaks due to damaged vessels, so it is rich in protein and contains many inflammatory cells.

In abdominal effusions, a transudate typically has low protein content (usually under about 3 g/dL) and low cellularity (fewer cells). An exudate, on the other hand, has high protein content (over about 3 g/dL) and high cellularity (many cells). This combination—low protein with low cellularity for transudate, and high protein with high cellularity for exudate—matches the correct interpretation. The distinction helps point toward non-inflammatory causes like hydrostatic or oncotic imbalance for transudates, versus inflammatory or infectious processes for exudates.