Pleural effusion obscuring pulmonary echinococcosis: diagnosis by cytology

Echinococcosis or hydatid disease , caused by larvae of the tapeworm Echinococcus, is frequently seen in an endemic country like India. A single organ is involved in 85-90% cases, pulmonary involvement occurs in 10 - 30% of cases, being second only to the hepatic involvement. Besides anaphylactic reactions a pulmonary hydatid cyst may be complicated by rupture into neighbouring structures like bronchi and pleural cavity with or without infection. We report an unusual case of ruptured hydatid disease in pleural cavity rarely seen in adults diagnosed by fine needle aspiration cytology. A 45 year old male came to our emergency department in shock with symptoms of shortness of breath and altered mental status from the previous day. Radiograph showed massive left sided pleural effusion and therapeutic aspiration was done. Pleural fluid cytology showed few hydatid scolices. Serum echinococcal antigen was also tested to be positive. CT scan revealed pleural effusion with multiple air pockets and pleural thickening on left side, and loculated cyst with septae on right side, thereby confirming the diagnosis as active pulmonary hydatid cyst with rupture into the pleural cavity, which is not a common finding in adult population. Hydatid cyst rupture should be considered in the differential diagnosis of cases with pleural effusion. Rupture of a pulmonary hydatid cyst into the pleural cavity is rare, but represents the most serious complication of the hydatid disease. In regions where echinococcal disease is endemic, a high level of clinical suspicion is necessary for diagnosis and appropriate management of this condition.