Computed Tomography (CT) Findings of Pulmonary Hydatid Cysts in Children and the Factors Related to Cyst Rupture

BACKGROUND The lungs are the most common site of hydatid cysts in children. Rupture is the main complication of cysts causing morbidity and mortality. In this study we aimed to comprehensively describe the CT signs for cysts and analyze the relationship of cyst ruptures to the diameter and location of cyst. MATERIAL AND METHODS A total of 145 cysts from 102 patients, aged 17 years or younger, who underwent a multi-detector computed tomography (MDCT) evaluation and had surgically proven pulmonary hydatid disease were included retrospectively. The CT images were analyzed for radiologic findings and signs of cyst rupture. RESULTS The cysts had a mean diameter of 5.45±3.03 cm. Most of the patients had a solitary cyst (70.6%). The most common lobes involved were the lower lobes (58.6%). Peripherally located cysts were more common than central cysts. The overall number of ruptured cysts was 69 (47.5%). The most common sign was the waterlily sign with a prevalence of 24.6%. After exclusion of cysts of 1 cm, the mean cyst diameter was 6.23±2.83 cm in the unruptured group and 5.02±2.80 cm in the complete ruptured group (p=0.020). The mean cyst diameter was 6.38±3.11 cm for centrally located cysts, and 4.31±2.37 cm for peripherally located cysts (p<0.0001). CONCLUSIONS Pulmonary hydatid cysts commonly presents as solitary cysts with a predilection for lower lobes and the peripheral regions of the lung. Peripherally located cysts are more common but smaller than centrally located cysts. Radiologists should also be aware of atypical imaging findings of cyst rupture, and radiologic signs should be explored during radiologic evaluation.