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What is Pneumatosis and explain in detail?
Pneumatosis is the abnormal presence of air or other gas within tissues.In the lungs, emphysema involves enlargement of the distal airspaces, and is a major feature of chronic obstructive pulmonary disease (COPD). Other pneumatoses in the lungs are focal (localized) blebs and bullae, pulmonary cysts and cavities.
Pneumoperitoneum (or peritoneal emphysema) is air or gas in the abdominal cavity, and is most commonly caused by gastrointestinal perforation, often the result of surgery.
Pneumarthrosis, the presence of air in a joint, is rarely a serious sign.

Lung cysts
A lung cyst, or pulmonary cyst, encloses a small volume of air,  and has a wall thickness of up to 4 mm. A minimum wall thickness of 1 mm has been suggested, but thin-walled pockets may be included in the definition as well