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.[3] A minimum wall thickness of 1 mm has been suggested,[3] but thin-walled pockets may be included in the definition as well.[4] Pulmonary cysts are not associated with either smoking or emphysema.[5]
A lung cavity has a wall thickness of more than 4 mm.[3]
Gastric pneumatosis (or gastric emphysema) is air or gas cysts in the stomach wall[6]
Joints
Pneumarthrosis is the presence of air in a joint. Its presentation on radiography is a radiolucent cleft often called a vacuum phenomenon, or vacuum sign.[7] Pneumarthrosis is associated with osteoarthritis and spondylosis.[8]
Pneumarthrosis is a common normal finding in shoulders[7] as well as in sternoclavicular joints.[9] It is believed to be a cause of the sounds of joint cracking.[8] It is also a common normal post-operative finding at least after spinal surgery.[10] Pneumarthrosis is extremely rare in conjunction with fluid or pus in a joint, and its presence can therefore practically exclude infection.[8]
A vacuum sign, or vacuum phenomenon, is a normal finding on shoulder X-rays.
Other
Subcutaneous emphysema is found in the deepest layer of the skin. Emphysematous cystitis is a condition of gas in the bladder wall. On occasion this may give rise to secondary subcutaneous emphysema which has a poor prognosis.[11]
Pneumoparotitis is the presence of air in the parotid gland caused by raised air pressure in the mouth often as a result of playing wind instruments. In rare cases air may escape from the gland and give rise to subcutaneous emphysema in the face, neck, or mediastinum.[12][13]
Terminology
The term pneumatosis has word roots of pneumat- + -osis, meaning "air problem/injury".
References
^"Medical Definition of PNEUMATOSIS". www.merriam-webster.com. Retrieved 31 July 2021.
^page 64 in: Adrian Shifren (2006). The Washington Manual Pulmonary Medicine Subspecialty Consult, Washington manual subspecialty consult series. Lippincott Williams & Wilkins. ISBN 9780781743761.
^ a b cDr Daniel J Bell and Dr Yuranga Weerakkody. "Pulmonary cyst". Radiopaedia. Retrieved 2019-05-01.
^Araki, Tetsuro; Nishino, Mizuki; Gao, Wei; Dupuis, Josée; Putman, Rachel K; Washko, George R; Hunninghake, Gary M; O'Connor, George T; Hatabu, Hiroto (2015). "Pulmonary cysts identified on chest CT: are they part of aging change or of clinical significance?". Thorax. 70 (12): 1156–1162. doi:10.1136/thoraxjnl-2015-207653. ISSN 0040-6376. PMC 4848007. PMID 26514407.
^Araki, Tetsuo. "Pulmonary cysts identified on chest CT:are they part of ageing change or of clinical significance" (PDF). Retrieved 19 January 2019.