The air bubble sign is seen in CT of complicated (ruptured or infected) pulmonary hydatid cyst and refers to small bubbles of gas within the periphery of pulmonary mass and is helpful, particularly in endemic areas, in suggesting the diagnosis over other masses (e.g. metastases or primary lung tumours) 1,2. It is thought to represent air tracking between the pericyst and the hydatid cyst membrane 1.
It should not be confused with the similarly named sign of tension pneumocephalus: see air bubble sign (tension pneumocephalus).
- 1. Yuncu G, Ors Kaya S, Sevinc S, et al. The diagnostic value of the ‘Air Bubble Sign’ in complicated pulmonary hydatid cysts. J Thorac Cardiovasc Surg. 2007;133:1524–74.
- 2. Singh U, Kumar S, Gour H, Singh N, Ramaraj M, Mittal V, Jhim D. Complicated hydatid cyst and "air bubble" sign: a stepping-stone to correct diagnosis. (2015) The American journal of case reports. 16: 20-4. doi:10.12659/AJCR.892621 - Pubmed