Single giant isolated hydatid cyst in left lung: a rare case report

Hydatid disease is a zoonotic parasitic infection caused by Echinococcus granulosus. Humans are accidental intermediate hosts. Hydatid disease is transmitted by the fecal-oral route through the ingestion of eggs of Echinococcus granulosus. Dogs (and other canines) are definitive host. Adult tapeworm lives in their intestines and sheds eggs in feces. Sheep, goats, cattle, sometimes humans (accidental) are intermediate host. In Humans infection occurs by Ingestion of eggs which hatch in the intestine to form larvae (oncospheres)which penetrate the intestinal wall and enter bloodstream to lateron lodge in liver, lungs, or other organs and form hydatid cysts. The lungs are the second most common site after the liver. Pulmonary hydatid cysts account for about 10–30% of all hydatid disease cases worldwide (1). Among these, single isolated pulmonary hydatid cysts (i.e.in lung only, without liver involvement) are reported in approximately 25–40% of pulmonary cases(2), Right lung more common than left. But left lung hydatid cysts can still occur, usually in lower lobes. Herein we present a rare case of left upper lingual hyatid cyst in a 16 yr old adolescent boy that was misdiagnosed as tuberculous loculated effusion in local health center. When sputum specimen was stained by acid-fast staining for detection of Mycobacterium tuberculosis, hooklets of Echinococcus granulosus were observed. A simple chest X-ray showed a homogeneous opacity in the upper and middle part of the left lung. Computed tomography scan verified existence of thin walled caviar lesion with irregular air–fluid level and was diagnosed as hyatid cyst, which was later confirmed during surgical removal. Misdiagnoses of pulmonary hydatid cyst may even lead to irreparable damages. Therefore, accurate diagnosis is necessary to prevent severe complications.