Seronegative, complicated hydatid cyst of the lung: A case report.

Cystic echinococcosis (CE) is an important helminthic zoonotic disease that commonly affects the liver and lungs. Imaging methods and serology establish the diagnosis in most cases. Chest x-ray can diagnose uncomplicated pulmonary hydatid cysts, whereas superinfection and/or rupture of the hydatid cyst (complicated cysts) may change the radiographic appearance and lead to delayed diagnosis and treatment. We report the case of a patient with hemoptysis and chest pain, where computer tomography scan of the lung suggested a large, ruptured hydatid cyst. However, serological tests with indirect hemagglutination (IHA)for antibodies were negative, and there was massive growth of in sputum. Based on this, we concluded that the patient had a bacterial lung abscess. The diagnosis of CE was only made after surgical removal of the cyst followed by microscopy and polymerase chain reaction.