title: Radiological characteristics of pulmonary hydatid disease in children: less common radiological appearances.
abstract: OBJECTIVE
  To evaluate the chest roentgenogram and CT characteristics of pulmonary hydatid disease (PHD).
  
  
  METHODS
  Forty-seven (27 male and 20 female, aged between 3 and 11 years) consecutive pediatric patients with surgically proven pulmonary hydatid cysts were enrolled for the study. Posteroanterior and lateral chest roentgenograms, CT of the chest, and laboratory findings (latex agglutination, Casoni skin test, and eosinophil count) were obtained from all of the patients. The radiological features (localization, internal architecture, number, diameter) were determined.
  
  
  RESULTS
  On CT examination, a total of 79 cysts were determined. On chest roentgenogram, 57 of 79 cysts were detected in all patients. Single cysts were seen in 33 patients, while multiple cysts were seen in 14. Median CT density of the cysts was 21 Hounsfield units (HU) (0-80). There were six giant cysts (>10 cm of cyst diameter). The crescent sign, water lily sign, and air-fluid level were seen in two, five and eight of the cysts, respectively. Apart from the classically described features of pulmonary hydatid cysts of the lung, a crescent-shaped rim of air at the lower end of the cyst (inverse crescent sign) was detected in three cysts. All of the liquid content of the cyst was expelled to the bronchial system (dry cyst sign) was observed in seven cysts. There were two infected cysts. Heavily calcified curvilinear cyst wall was present in one cyst. Pericystic reaction in the lung tissue was observed in five patients. Other features included pleural effusion (n=2), mediastinal shift (n=6) and atelectasis (n=7).
  
  
  CONCLUSIONS
  Chest roentgenogram is helpful for diagnosis of intact cysts but, it is impossible to define entire morphology of the complicated cysts. CT imaging recognize certain details of the lesions and discover others that are not visible by conventional radiography. In conclusion, CT examination should be done to elucidate cystic nature of the lung mass and for accurate localization in the preoperative period. In addition, inverse crescent sign should be recognized as feature of pulmonary hydatid cysts on CT.
authors.affiliation: Department of Radiology, School of Medicine, Zonguldak Karaelmas University, 67600 Kozlu/Zonguldak, Turkey. sunarerdem@yahoo.com
authors.forename: C Zuhal
authors.initials: CZ
authors.lastname: Erdem
authors.forename: L Oktay
authors.initials: LO
authors.lastname: Erdem
mesh_terms: D002648:Child; D002675:Child, Preschool; D004445:Echinococcosis, Pulmonary / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging*; D008297:Male; D014057:Tomography, X-Ray Computed