Pneumoperitoneum - the importance of projection

Case contributed by Ian Bickle


This 35 year-old patient presented to A and E with upper abdominal pain of short duration.

Patient Data

Age: 35
Gender: Male

Initial films discussed with duty radiologist by the surgeon as concerns over a perforation but 'normal films'


At presentation a SUPINE chest x-ray and abdominal radiograph were performed for the clinical indication of abdominal pain.

SUPINE CXR: No free subdiaphragmatic gas

ABDOMINAL FILM:  Unusual area of lucency overlying the right upper quadrant, which appears extra-luminal in nature

REPEAT CXR IN THE ERECT POSITION (20 MINUTES LATER):  Large volume pneumoperitoneum.

Case Discussion

Sometimes the best lessons in life are the simple ones.

The learning points from this case are:

1.  Always interrogate the film characteristics - the projection is important to find the pathology

2.  Patients are always served better when clinicoradiological discussion takes place

3.  Even with advanced imaging modalities plain radiographs are still important and interesting

Pneumoperitoneum is more easily identified on the erect CXR, than the AXR, but a number of signs of free gas on AXR have been described.

These include:  the falciform ligament sign, triangles of gas, the football sign, inverted V sign and 'right upper quadrant gas sign'.

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