what is free air?
Started by obiwan
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You're not supposed to have free air in the abdomen. If you do, there's a hole somewhere that isn't supposed to be there (viscus perforation, for example).
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Free air is air in the peritoneum. All air should be external to the body (remember the gi tract and pulmonary space are connected to the outside through tubes and separated from the internal compartments and is therefore still outside the body). You can get air in the peritoneum via operations which allow air from outside the body in (which will slowly resolve over a couple of weeks) or through perforation of one of the air filled tubes. Free air can be detected via a chest x-ray, abdominal films, or a CT scan. The CT scan is the most sensitive, but is also the most expensive and exposes the patient to the most radiation. On a CXR you can look right under the diaphragm and note a clear or nearly clear stripe (the air rises and the peritoneal fluid sinks). On abdominal films you can often make out free air depending upon the position of the patient. It may be difficult/impossible to see free air in a supine patient, as the clear area is masked by the fluid and bowel behind it.
B
Blade28
Nope. Totally different situations.
Air-fluid levels are commonly seen in upright abdominal x-rays, in patients with a small bowel obstruction. Look for the classic "stepwise" pattern.
As noted above, free air in the abdomen may show perforation of a hollow viscus.
Or post-surgical changes.
Nothing more fun than a breathless call from the Radiology resident at 2am for free air on the patient you unzipped 24hrs ago . . .
As noted above, clinically correlate it all, or the surgeons will laugh at you . . .
For the last three radiographs on which I've diagnosed free air the provided clinical history has been "fever", "follow-up", and "shortness of breath".
Providing a brief, but pertinent, clinical history can go a long way.
Providing a brief, but pertinent, clinical history can go a long way.
Why were you taking x-rays of a belly 1 day after a laparotomy?
B
Blade28
To check Dobbhoff/NGT placement?
Tube-check for a G-tube or J-tube that was dislodged?
Sudden distention and N/V that's more than simple post-op ileus?
4
45408
is that useful for a Schleinberger/ASDF? what about an HIJKLMNOP?
Chest xray for decreased sats.
Probably wouldn't hurt to mention one more little gem with regards to free-air . . . those on high dose steroids can theoretically perf without much symptomology until much later in the disease process. So someone who has free air within the context of high dose steroids . . . have high clinical suspicion. What would my surgical friends want next, you know, ordered before I call you?
That makes sense. For some reason I was thinking KUB, not CXR.
I don't know. Maybe for a possibly dislodged NG. If sudden distention happened that close to the surgery, I think I would either get a CT or just go back in depending on my clinical suspicion.
Anyway, I was just curious because I couldn't recall ever getting one that close to a laparotomy, foreign body checks excluded.
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