Abdominal X-ray

Question 1

How would you structure an x-ray interpretation?

Answer 1

1. Confirm details
2. Assess image type and quality
3. Bowel and other organs
4. Bones
5. Calcification
6. Presenting an abdominal X-ray

Question 2

How would you confirm a patient’s details?

Answer 2

Patient details: name, date of birth and unique identification number.

Date and time the film was taken

Previous imaging: useful for comparison.

Question 3

How would you assess imagine type and quality?

Answer 3

1. Assess the projection of the abdominal X-ray.
   a. Anterior-posterior (AP) supine
   b. Anterior-posterior (AP) erect
2. Exposure:
   a. Assess the X-ray to ensure the whole abdomen is visible from the level of the diaphragm to the pelvis.
   b. Ensure the exposure is adequate to allow radiological assessment of both the small and large bowel.

Question 4

How would you ensure you have a structured approach to interpretation?

Answer 4

It’s important to have a systematic approach to interpreting abdominal X-rays as this decreases the risk of missing pathology.

In this guide we use the BBC approach:

1. Bowel and other organs: small bowel, large bowel, lungs, liver, gallbladder, stomach, psoas muscles, kidneys, spleen and bladder.
2. Bones: ribs, lumbar vertebrae, sacrum, coccyx, pelvis and proximal femurs.
3. Calcification and artefact (e.g. renal stones)

Question 5

What would you say about the bowel and other organs?

Answer 5

1. Differentiate between small and large bowel
2. Bowel diameter
3. Small bowel obstruction
4. Large bowel obstruction
5. Rigler’s (double wall) sign
6. Inflammatory bowel disease
7. Other organs and structures

Question 6

How would you differentiate between the small and large bowel?

Answer 6

The small bowel usually lies more centrally, with the large bowel framing it.

The small bowel’s mucosal folds are known as valvulae conniventes and are visible across the full width of the bowel.

The large bowel wall features pouches or sacculations that protrude into the lumen, known as haustra. In between the haustra are spaces known as plicae semilunaris. The haustra are thicker than the valvulae conniventes of the small bowel and typically do not appear to completely traverse the bowel. This distinction is unfortunately unreliable as dilated large bowel can have a haustral pattern that does, in fact, traverse the bowel.

Faeces have a mottled appearance and are most often visible in the colon, due to trapped gas within solid faeces.

Question 7

What are normal diameters for the bowel?

Answer 7

The upper limits for the normal diameter of different bowel segments are as follows:

Small bowel: 3cm
Colon: 6 cm
Caecum: 9 cm

This is often referred to as the ‘3/6/9 rule’.

Question 8

How would you spot small bowel obstruction on an xray?

Answer 8

Typical abdominal X-ray features of small bowel obstruction include dilation of the small bowel (>3cm diameter) and much more prominent valvulae conniventes creating a ‘coiled-spring appearance‘.

Question 9

What causes small bowel obstruction?

Answer 9

Adhesions (75%)

Also abdominal hernias, intrinsic or extrinsic compression

When interpreting an abdominal X-ray you should always inspect the inguinal regions, particularly if considering a hernia as a cause of small bowel obstruction, as they are often fairly obvious (even on plain abdominal X-rays).

Question 10

How would you spot large bowel obstruction on an xray?

Answer 10

Typical abdominal X-ray findings in volvulus differ depending on the sub-type:

1. Sigmoid volvulus: a characteristic ‘coffee bean’ appearance.
2. Caecal volvulus: often described as having a fetal appearance.

Question 11

What causes large bowel obstruction?

Answer 11

The most common causes of large bowel obstruction include colorectal carcinoma and diverticular strictures. Less common causes include hernias and volvulus.

Question 12

What is Rigler’s (double wall) sign?

Answer 12

In healthy individuals, only the inner wall of the bowel should be visible on an abdominal X-ray. The presence of free air within the abdomen (pneumoperitoneum) can result in both sides of the bowel wall becoming visible (this is known as Rigler’s sign).

Question 13

What causes Rigler’s (double wall) sign?

Answer 13

Perforated abdominal viscus (e.g. perforated bowel, perforated duodenal ulcer) and recent abdominal surgery.

You should look closely for free air under the diaphragm on an erect chest X-ray if you suspect pneumoperitoneum.

Question 14

What are features of IBD on an abdominal X-ray?

Answer 14

1. Thumbprinting: mucosal thickening of the haustra due to inflammation and oedema causing them to appear like thumbprints projecting into the lumen.
2. Lead-pipe (featureless) colon: loss of normal haustral markings secondary to chronic colitis.
3. Toxic megacolon: colonic dilatation without obstruction associated with colitis.

Question 15

What would you say about other organs?

Answer 15

Lungs: inspect the lung bases for pathology (e.g. consolidation) as abdominal pain can, in some cases, be caused by basal pneumonia.

Liver: a large right upper quadrant structure.

Gallbladder: rarely visible on an abdominal X-ray, however, you should quickly inspect for calcified gallstones and cholecystectomy clips.

Stomach: visible between the left upper quadrant and midline, containing a variable amount of air.

Psoas muscles: the lateral edge is marked by a relatively straight line either side of the lumbar vertebrae and sacrum.

Kidneys: both are often visible, the right kidney is lower than the left due to the presence of the liver on the right.

Spleen: located in the left upper quadrant, superior to the left kidney.

Bladder: has a variable appearance depending on the fullness of the bladder.

Question 16

What bony structures should you identify on an abdominal xray?

Answer 16

Ribs
Lumbar vertebrae
Sacrum
Coccyx
Pelvis
Proximal femurs

A wide range of bony pathologies can be identified on abdominal X-ray including fractures, osteoarthritis, Paget’s disease and bony metastases.

Question 17

What calcifications can be seen on an abdominal xray?

Answer 17

Calcified gallstones in the right upper quadrant
Renal stones/staghorn calculi
Pancreatic calcification
Vascular calcification
Costochondral calcification
Contrast (e.g. following a barium meal)
Surgical clips
Jewellery

Question 18

How would you present an abdominal xray?

Answer 18

“This is a supine AP abdominal radiograph of Jayne Lister, date of birth 11th April 1970. The film is of good quality with adequate exposure. No prior imaging is available for comparison. Both the small and large bowel appear within normal limits. Other abdominal viscera appear normal within the limits of this projection. No obvious bony pathology is identified. No abnormal calcification is visible. In summary, this is a normal plain radiograph of the abdomen.”