Presentation
Cough and breathlessness. Abnormal chest x-ray.
Patient Data
Two well-defined cystic lesions, one in the posterior segment of the left upper lobe and the other in the lateral basal segment of the left lower lobe.
Patient was managed conservatively.
Cavitation of both lesions which now contain detached membranes (water lily sign).
Case Discussion
Hydatid disease is a parasitic infection most commonly caused by the larval stage of Echinococcus granulosus 1,2. In adults, the liver is the most commonly affected organ followed by the lungs but in the pediatric population 1 the lungs are the most common site of involvement 3,4.
In the case of pulmonary hydatid, lower lobe involvement is common with the right lower lobe being more commonly affected 1, 5-7.
Uncomplicated hydatid cysts appear as well-defined fluid attenuation lesions with smooth walls. Calcification is rare in pulmonary hydatid, unlike hepatic hydatid disease 2,8,9.
CT features vary depending on whether the rupture is contained or not. In cases of contained rupture the air crescent sign or inverse crescent sign may be seen.
Accumulation of air between the endocyst and pericyst causes rupture of the endocyst and collapse of the membranes. Cumbo sign 10 and water lily sign 10,11 are features of a complete rupture.
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