Imaging Case of the Week 97

This PA erect chest x-ray is from a 40 year old female patient who has presented with abdominal pain. What can you deduce from the x-ray?

PA erect

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[peekaboo_link name=”Answer”]Answer[/peekaboo_link] [peekaboo_content name=”Answer”]

The lung fields are clear and the cardiomediastinal contour is normal. However, there appears to be an air crescent under the left diaphragm. Is this pneumoperitoneum?

The patient indeed had a large pneumoperitoneum, secondary to a perforated antral ulcer; the following CT scans were obtained just an hour after the plain x-ray!

CT abdo

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CT pneumoperitoneum

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  • About 76% of perforated peptic ulcers will reveal free air on erect chest x-rays.
  • In patients who are unfit or too sick to stand upright, a left lateral decubitus x-ray can show a small pneumoperitoneum.
  • Both erect cxr and left lateral decubitus abdominal x-rays require the patient to be in position for at least 10 mins to allow sufficient time for the air to rise.
  • On the left, it can be difficult to distinguish free air from gas in the stomach/colon.
  • CT is the most sensitive investigation for the detection of free peritoneal gas.

(Reference: Textbook of Radiology and Imaging by Sutton)