How do you approach diagnosis of a unilateral pleural effusion — when is thoracentesis mandatory?

1 Answer

Approach to Unilateral Pleural Effusion: Step 1 - Confirm and Quantify: - CXR: Blunting of costophrenic angle (>200 mL needed) - Ultrasound: Superior to CXR, identifies loculations, guides thoracentesis Step 2 - Thoracentesis MANDATORY when: - First presentation of unilateral effusion (your patient) - Bilateral effusions of unequal size - Fever or other infection signs - Unexplained effusion despite clinical diagnosis - Patient not improving as expected Step 3 - Fluid Analysis - Light's Criteria (Exudate = ANY of): 1. Pleural LDH/serum LDH >0.6 2. Pleural protein/serum protein >0.5 3. Pleural LDH >2/3 upper limit of normal serum LDH Transudate causes: CCF, cirrhosis, nephrotic syndrome, hypothyroidism Exudate causes: Pneumonia, TB, malignancy, PE, rheumatoid Additional Tests on Fluid: - Glucose (low in TB, RA, empyema) - pH (low <7.2 = empyema, malignancy) - Cell count (>10,000 neutrophils = empyema; lymphocytes = TB/malignancy) - AFB culture and ADA (>40 U/L suggests TB) - Cytology (malignant cells) - Triglycerides (if chylothorax suspected) For your patient: - Unilateral effusion, no prior disease = mandatory thoracentesis - Light's criteria to classify, then work up cause accordingly