title: CT in pulmonary hydatid disease: unusual appearances.
abstract: OBJECTIVE
  To study the CT features of pulmonary hydatid disease.
  
  
  METHODS
  Thirty-two consecutive patients with surgically proven pulmonary hydatid cysts.
  
  
  METHODS
  SheriKashmir Institute of Medical Sciences, Srinagar, Kashmir, India, a tertiary-care referral center.
  
  
  METHODS
  CT of the chest was obtained in all cases on Somatom DR double rotate CT scanner (Siemens; Erlangen, Germany).
  
  
  RESULTS
  Forty cysts of different size and shapes were encountered, 34 of them being ruptured. CT density of the cysts varied from - 42 to 160 Hounsfield units (HU; median, 15.5 HU). Apart from the classically described features of pulmonary hydatid disease, a crescent-shaped rim of air at the lower end of the cyst (inverse crescent sign) was seen in three cysts, and a bleb of air in the wall of two as-yet unruptured cysts (signet ring sign). Thick wall (>10 mm) was observed in four cysts, and each of them had associated evidence of infection.
  
  
  CONCLUSIONS
  Inverse crescent sign, signet ring sign, high CT density, and thick wall should be recognized as features of pulmonary hydatid cysts on CT.
authors: Departments of Internal Medicine, SheriKashmir Institute of Medical Sciences, Srinagar, Kashmir, India. parvaizk@hotmail.com
authors: P A
authors: PA
authors: Koul
authors: A N
authors: AN
authors: Koul
authors: A
authors: A
authors: Wahid
authors: F A
authors: FA
authors: Mir
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D004445:Echinococcosis, Pulmonary / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed