Intramural bowel gas, also known as pneumatosis intestinalis, refers to the clinical or radiologically finding of gas within the wall of the bowel.
There are different terminologies in the medical literature, such as pneumatosis intestinalis, pneumatosis coli, and pneumatosis cystoides intestinalis. Pneumatosis coli is used when only the colic wall is involved and is generally an incidental finding in asymptomatic patients. Pneumatosis cystoides intestinalis is descriptive for multiple gaseous cysts along the bowel wall.
Intramural gas can be seen in intestinal ischaemia and eventually bowel infarction. This is the most concerning aetiology for intramural gas.
Gas in the bowel wall in the neonatal period, whatever its shape, is diagnostic of necrotising enterocolitis.
Asymptomatic pneumatosis intestinalis may result from a variety of interrelated contributing factors including:
- mucosal integrity
- intraluminal pressure
- bacterial flora
- intraluminal gas
Gas tracks along the bowel wall, appearing as either linear, which are usually submucosal, or rounded cystic "bubbly" collections, which are usually subserosal 1. Where they join, they may outline the circumferenial margin of the bowel, creating rings.
Gas in the bowel wall is most easily identified with CT and plain radiography, but ultrasound and MRI can be usefully in paediatric patients where there is a desire to avoid radiation.
Other imaging findings help differentiate sinister causes from benign causes, such as 4:
- dilated bowel
- bowel wall thickening
- abnormal bowel wall enhancement
- portal venous gas
- atherosclerosis and vascular occlusion
The presence of pneumomediastinum favours a benign cause 1.
- bowel ischaemia and infarction
- inflammatory bowel disease
- steroid use
- autoimmune disease and immunosuppression
- connective tissue disorders
- primary pneumatosis
- pulmonary disease
- post endoscopy / colonoscopy
- post operative
- post enteric tube
- CT colonography
- pseudopneumatosis (mimics) include:
- gas trapped between bowel wall and luminal contents
- gas trapped by opposing mucosal folds
- gas bubbles adherent to bowel wall
From a clinical perspective, it is essential not to confuse the incidental imaging finding of asymptomatic pneumatosis with symptomatic colonic perforation because the treatment is significantly different 2.
- 1. Devos AS, Blickman JG, Blickman JG. Radiological Imaging of the Digestive Tract in Infants and Children. Springer Verlag. (2007) ISBN:3540407332. Read it at Google Books - Find it at Amazon
- 2. Pickhardt PJ, Kim DH, Taylor AJ. Asymptomatic pneumatosis at CT colonography: a benign self-limited imaging finding distinct from perforation. AJR Am J Roentgenol. 2008;190 (2): W112-7. doi:10.2214/AJR.07.2843 - Pubmed citation
- 3. Ho LM, Paulson EK, Thompson WM. Pneumatosis intestinalis in the adult: benign to life-threatening causes. AJR Am J Roentgenol. 2007;188 (6): 1604-13. doi:10.2214/AJR.06.1309 - Pubmed citation
- 4. Martin L. Gunn. Pearls and Pitfalls in Emergency Radiology. ISBN: 9781139619899