40 year old male farmer who has livestock was admitted with paroxysms of cough and expectoration. Clinical examination was normal. Chest X-ray showed a large thin walled cavity containing membranes in the lower lobe of the left lung with left pleural effusion. CT scan of the chest revealed a 'water lily' sign. What is the most probable diagnosis?
High-Yield Explanation
Water lily sign although rarely seen is pathognomonic of echinococcosis. Cyst with a freely floating endocyst.