CT in pulmonary hydatid disease: unusual appearances.

Abstract

OBJECTIVE: To study the CT features of pulmonary hydatid disease. 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, 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.