Clinical features

1. Ask your patient to sit upright or stand for 5 minutes to allow any free pleural fluid to drain to the lung base. 
2. Place the stethoscope diaphragm 3 cm below the 12th rib in the midclavicular line. 
3. Percuss directly with your free hand (by finger flicking or with the pulp of a finger) along three or more parallel lines from the apex of each hemithorax perpendicularly down toward the base. 
4. Pleural effusions can be confirmed by asking a patient to lean to one side and then reassess the fluid level to see whether it had shifted. 

Why?

Auscultatory percussion can help diagnose a pleural effusion

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
suspected pleural effusion c (pre-test probability: %)	pleural effusion (chest X-ray)	dullness on auscultatory percussion	19 (9.8 to 35)	-	0.045 (0.019 to 0.11)	-