Subdiaphragmatic free gas is one of the ways of detecting presence of free intraperitoneal air (i.e. pneumoperitoneum). It is the presence of free, extraluminal air in the anterior subhepatic space.
As little as 1 mL of free gas can be detected but the patient may be needed to be kept in upright position for about 10 minutes for the air to rise.
Erect chest x-rays covering the upper abdomen are often considered the best for detecting free subdiaphragmatic gas but an erect abdominal x-ray covering the lung bases will be just as sensitive.
- Chilaiditi syndrome
- subdiaphragmatic abscess
- omental fat interpositioned between the liver and diaphragm
- subpulmonary pneumoperitoneum
- enlarged gastric bubble
- gas containing liver hematoma
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