Abdominal Xray Signs And How To Read An AXR

Question 1

What is the system for reading an AXR?

Answer 1

Overview: work from rectum backwards - distal to proximal

1. Check for normal structures:
   A. rectum
   B. Large bowel - haustral markings don’t extend across lumen (large bowel isn’t lined)
   C. Small bowel - valvulae extend across entire lumen (small bowel is lined)
   D. Kidneys, ureters, bladder - KUB
   E. Organs - stomach, liver, GB, spleen, pancreas
   F. Bones - ribs 10-12, lumbar/sacral vertebrae, ilium/part of ischium, hip joints, femur head

2. Gas pattern (gas=black on xrays)
A. Stomach - should always be there
B. Small bowel - 2/3 loops visible
C. Sigmoid/rectum - almost always there
More gas than this may mean obstruction

Question 2

Why is it unusual to see solid stool in the ascending colon?

Answer 2

The ascending colon is processing liquid stool direct from the ileum, this means constipation normally occurs in the distal colon (led sided).

Question 3

Why might you see large bowel dilatation with small bowel dilatation?

Answer 3

Obstruction of the large bowel with reflux through the ileocaecal valve causing gas to build in the small bowel too.

Question 4

Why is large bowel dilatation without small bowel dilatation worrying?

Answer 4

This implies that none of the gas in the large bowel is being let back in to the small bowel, and increases the risk of perforation.

Question 5

What does small bowel obstruction look like on AXR?

Answer 5

Large bowel are not visible since they have received no stool or air thanks to the obstruction.

Dilated bowel has lines that completely cross the lumen, indicating it is small bowel and not large bowel.

The entire small bowel may be dilated due to the lack of valves within the small bowel, but since it is a closed system between the ileocaecal valve and the pyloric sphincter.

Question 6

What does a sigmoid volvulus look like?

Answer 6

A sigmoid volvulus is a twist of the sigmoid colon. (Like twisting the midsection of a piece of string)

Coffee bean sign - volvulus looks like coffee bean, apex points up at the RUQ and the bottom pointed at the LLQ where the twist has occurred.

Question 7

What does a caecal volvulus look like?

Answer 7

The apex points upwards at the LUQ, and it is not shaped like a coffee bean.