Abdominal X-ray - System and anatomy
Image data and quality

Key points

  • Check the patient details
  • Check which projection has been used - AP or decubitus
  • If assessing for perforation always look at the ERECT chest X-ray
  • Check you can see the whole abdomen

Patient and image data

You should always check that the image data refers to the correct patient and that the X-ray is the current examination.

Check the image data to see if it is a standard Anterior-Posterior (AP) supine projection.

Supine Anterior-Posterior (AP) projection

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Supine Anterior-Posterior (AP) projection

  • Abdominal X-rays are usually acquired using an AP (Anterior-Posterior) projection (X-rays pass through the patient from front to back), with the patient positioned supine.

Erect chest X-ray

If perforation of the bowel is suspected then an ERECT chest X-ray must be requested. This is the most sensitive plain radiographic study to detect the presence of free gas in the abdomen.

Erect Chest X-ray - Pneumoperitoneum

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Erect Chest X-ray - Pneumoperitoneum

  • Pneumoperitoneum (free gas in the abdomen) does not always indicate perforation of an abdominal viscus.
  • This patient had an abdominal operation shortly before this image was acquired, which accounts for the free gas seen under the diaphragm.

Other projections

Occasionally patients are too ill to be positioned erect. In this case a CT scan may be appropriate, or a 'decubitus' radiograph can be obtained. For a decubitus image the patient lies on their side and X-rays pass through the body from back to front. For a 'left decubitus' the patient lies on their left.

Decubitus positioning

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Decubitus positioning

  • Use of the decubitus position can demonstrate pneumoperitoneum in a patient who cannot be positioned for an erect chest X-ray to be performed. Gas rises to the upper part of the abdomen and so will be seen on one side of the abdominal X-ray image.
  • This projection is not commonly performed.

Abdominal X-ray quality

Abdominal X-rays provide limited information at the best of times. Often anatomical structures are not clearly demonstrated, and abnormalities can be obscured by normal anatomical structures. For example, small renal stones may be obscured by overlying bowel.

When an image is of low quality there is often little that can be improved and therefore repeating images is usually unfruitful.

The whole abdomen should be included. Often two images are required to view the entire abdomen from the diaphragm to the hernial orifices, and from left to right abdominal walls. Large patients may require more images.