**Question:** Pleural effusion with very low glucose is

A. Transudate
B. Exudate
C. Transudate with high protein
D. Transudate with low protein

**Correct Answer:** B. Exudate

**Core Concept:** Pleural effusion is a condition where excess fluid accumulates in the pleural space, the space between the two pleural layers that line the lungs and chest wall. This fluid can be classified into two types: transudate and exudate, based on the levels of glucose and protein in the fluid.

**Why the Correct Answer is Right:** An effusion with very low glucose (40 mg/dL). In this case, the effusion would not be expected to have very low glucose levels.

B. Transudate with high protein is another classification but does not address the glucose content. Pleural effusions with high protein levels can be transudates, but the question asks for effusions with very low glucose levels.

C. Transudate with low protein occurs in conditions like heart failure, where there is a decrease in plasma protein levels, leading to low protein content in the effusion. However, the question specifically mentions very low glucose levels, which distinguishes it from other transudates.

**Clinical Pearl:** A low glucose effusion with high protein (transudate with low protein) is a clinical clue for heart failure, while a low glucose effusion with normal protein (transudate with low glucose) is a clue for pulmonary hypertension. These distinctions are crucial for differentiating between the causes of pleural effusions and guiding appropriate diagnostic and therapeutic decisions.