Teaching Case

A 14-year-old young male patient from a rural area with a history of trauma was consulted for pain and haemoptysis in the emergency room.

Chest x-ray reveals presence of air-fluid level in the lower third of the left hemithorax. Computed tomography confirms the presence of a cystic lesion with air - fluid level, internal membranes "floating", serpinginous hyperattenuating membranes and pleural effusion. He undergoes surgery. Uncomplicated postoperative course.

Background: Hydatid disease is a parasitic zoonosis produced by the larval stage of Echinococcus tapeworm [1].
Clinical perspective: This pathology is an endemic entity in some countries of the world, mainly in agricultural and livestock areas, South America [1] being an example, especially in Chile.
It is important to spread the imaging findings, since there are sectors in Europe with high infection rates, which may present similar manifestations (Mediterranean region). [1]
Imaging perspective: This disease affects the liver, presenting characteristic imaging findings. However, secondary involvement due to haematogenous dissemination may occur in almost every other part of the body (lung, kidneys, spleen, brain, bone). Pulmonary involvement is the most frequent site of haematogenous dissemination in children and the second in adults. [1]
Rupture of a cyst is the most frequent complication. [2]
The modalities of study are radiography and computed tomography. CT is the modality of choice for diagnosis of complicated hydatid cyst. [2]
Key findings: In X-ray the presence of an air-fluid level is a sign of a complicated cyst. In CT the presence of a cystic lesion with air-fluid level and floating membranes (water lily sign), serpinginous hyperattenuating membranes (“serpent sign”) and pleural effusion suggest a complicated cyst. [2]
Teaching points: Imaging of pulmonary complicated cyst in a patient in an endemic area.