Abdominal x-ray review: ABDO X

Last revised by Daniel J Bell on 3 Apr 2023

Abdominal x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using ABDO X is a helpful and systematic method for abdominal x-ray review:

  • A: air - where it should and should not be

  • B: bowel - position, size and wall thickness

  • D: dense structures, calcification and bones

  • O: organs and soft tissues

  • X: eXternal objects and artifacts



Air should only be seen within the lumen of the bowel. Erect chest x-rays are more sensitive than abdominal radiographs to the presence of free intraperitoneal air. Signs of pneumoperitoneum on abdominal radiographs include:

Read more: abdominal x-ray assessment of air


Normal small bowel:

  • is located centrally within the abdomen

  • has folds running across the diameter of the lumen known as the valvulae conniventes

  • usually contains a small volume of air.

Normal large bowel:

  • is located peripherally

  • has folds that run part of the way across known as the haustral folds

  • usually contains some air or fecal matter.

In the presence of ascites, the bowel loops are clustered centrally.

The 3-6-9 rule refers to an approximate maximum size in centimeters of the small bowel, large bowel and cecum respectively.

Small bowel wall thickening is difficult to appreciate on plain radiography, whereas thickening of the large bowel is represented by thumbprinting.

Read more: abdominal x-ray assessment of bowel


Examine carefully all of the bones visible on abdominal radiographs:

  • lowest ribs

  • vertebral column 

  • pelvic bones

  • femoral heads and necks

Calcification within organs may be detected - in particular, look carefully for calcified renal tract or gallbladder stones.

Read more: abdominal x-ray assessment of densities


Abdominal radiographs are a blunt instrument for critical evaluation of the solid organs but information regarding pathological changes in size may be gleaned. The fat surrounding organs provides an interface which allows their contour to be seen. Remember to examine the lung bases for consolidation (which can cause abdominal pain) and the inguinal regions for signs of herniae.

Read more: abdominal x-ray assessment of organs and soft tissues

External objects and artifacts

A multitude of medical devices and foreign bodies may be detected on an abdominal radiograph.

Read more: abdominal x-ray assessment of external objects and artifacts

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Cases and figures

  • Figure 1: normal large bowel
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  • Figure 2: normal small and large bowel
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  • Figure 3: normal abdominal organs
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  • Figure 4: organs and soft tissues
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