A 45 year old man referred to pulmonology medicine

A 45 year old man referred to pulmonology medicine ward because of progressive dyspnoea over a one month period.He is a heavy alcohol drinker and has a smoking history of 10 years.He was diagnosed with chronic pancreatitis 5 month prior to presentation.On physical examination his vitals are normal except for dullness to percussion and decreased breath sound over the left hemithorax.The physician think of pleural effusion.Which is best investigation to diagnose pleural effusion?

Right lateral decubitis CXR

CT scan

USG

Left lateral decubitus CXR

Usg

Best inv: USG

Best Radiograph: Left lateral decubitus CXR

USG