Recognizing Free Air

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William Herring, M.D. © 2002

Remember

Air will rise to whatever is the highest part of the abdomen

The 3 Signs of Free Air

Air beneath diaphragm Both sides of bowel wall Falciform ligament sign

ERECT

Air beneath the diaphragm forms a crescentric lucency seen best on the right side over the liver

Air on both sides of the bowel wall (Rigler’s sign). Normally (see below) you do not see the bowel wall as a discrete line.

Normal

Falciform Ligament Sign

Air over the convexity of the liver on a supine view outlines the Falciform ligament, which is usually invisible.

These are the Causes of Free Air

Rupture of a hollow viscus Perforated ulcer Perforated diverticulitis Perforated carcinoma Trauma or instrumentation

Post-op 5–7 days NOT perforated appendix

Which of the following patients has free air?

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Yes

No

Does this patient have free air?

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Yes

No

Does this patient have free air?

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Yes

No

Does this patient have free air?

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Yes

No

Does this patient have free air?

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CorrectThere is Free Air

Both sides of the bowel wall (the stomach) are visible

Go Ahead

CorrectThere is No Free Air

The stomach is dilated, but both sides of the stomach wall are not visualized

Go Ahead

CorrectThere is No Free Air

None of the signs of free air is present here

Go Ahead

Both sides of the bowel wall are visualized here.

CorrectThere is Free Air

Go Ahead

WrongLook Again

Remember to look for the 3 signs of free air

Air beneath diaphragm Both sides of bowel wall Falciform ligament sign

Go Back

Congratulations, You Graduate

I know my Free Air