Objective: To study the CT features of pulmonary
Patients: Thirty-two consecutive
patients with surgically proven pulmonary hydatid cysts.
Setting: SheriKashmir Institute of Medical Sciences,
Srinagar, Kashmir, India, a tertiary-care referral center.
Interventions: CT of the chest was obtained in all cases on
Somatom DR double rotate CT scanner (Siemens; Erlangen,
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.