'Double-arch' sign and 'air-bubble' sign--two radiological signs of ruptured hydatid cyst in lung.

*Assistant Professor, **Professor, Department of Pulmonary Medicine, Medical College, Kolkata, West Bengal Received: 17.07.2012; Revised: 06.11.2012; Accepted; 09.01.2013 A fifty five year old male presented with episodes of scanty haemoptysis for two days, cough with expectoration for las t four years . Chest X – ray (CXR), posteroanterior view showed a homogeneous rounded opacity in left lower zone, and absolute eosinophil count was 1,200/ μL. Contrast enhanced computed tomography (CECT) scan of thorax showed a mass – like lesion in left lower lobe with air pockets within the lesion – the ‘air – bubble’ sign (Figure 1). Previous CXR of 6 months back revealed a cystic lesion with air – fluid level within it in the left lower zone, which was capped with a crescent of air – forming ‘double arch’ sign or Cumbo’s sign, another radiological sign which is pathognomonic for ruptured hydatid cyst (Figure 2). Anti – echinococcal IgG antibody was highly positive, i.e., 32.45 U/mL (normal value: < 8 U/mL, ELISA method). Hydat id disease i s caused by a parasite, Echinococcus granulosus. The diagnosis of echinococcosis is generally made on the basis of clinical history and ‘Double – arch’ sign and ‘Air – bubble’ Sign – Two Radiological Signs of Ruptured Hydatid Cyst in Lung