Abdominal X-Ray
Interpreting an Abdominal X-Ray is an essential skill for any junior doctor. It is a common investigation that you will be asked to order, and can be used to investigate a variety of conditions.
Learning how to interpret abdominal X-Rays is often a skill that medical students are expected to pick up as they shadow on the wards. Therefore, to help you learn this skill, you can use the following acronym DR BOB C.
By using this, you will be able to go through abdominal X-Rays in a systematic way to ensure you don’t miss any important details. It also gives you a great structure when you need to present the findings to your senior.
So if you are presented with a AXR like this, let’s see how to go through it.
D – Details
When starting with any Abdominal X-Ray, the first thing to do is to confirm that it is of the right patient. This will involve checking for the following features.
- Confirm Name
- Confirm Age
- Confirm DoB
- Confirm Date and Time of Film
- Is there anything to compare the film to?
Many patient’s who have prolonged admissions or a background of respiratory disease may have chronic AXR changes.
Therefore it is important to always ask whether there is a previous ABXR that you can compare to. This will help to identify whether any abnormality is longstanding or chronic.
R – RIPE
This is a sub-mnemonic. After you have confirmed that the AXR is for the correct patient, you should then comment on the film quality.
This involves mentioning 4 key features: Rotation, Inspiration, Projection and Exposure.
Whilst “Inspiration” is used more for Chest X-rays, keeping it in the acronym let’s you comment on the field of view.
R - Rotation
- Pelvic brim should be horizontal
- Spinous processes should be vertical against vertebral bodies
"I - Inspiration" (Field of View)
- Diaphragm to pelvis should be present
P - Projection
- The standard way to do an abdominal x-ray is anterior-posterior AP. This means that the plate is held behind the the patient and the X-Ray beam is aimed from in front of them.
- The AXR will usually state if it is taken AP or PR. As AP is the norm, if there is nothing written, then you can assume that it is taken PA
- Also check if it is taken in the erect or supine position, as this will influence where free air rises.
E - Exposure
- Exposure is how well you can see the structures.
- You should be able to see the vertebral bodies. This is a well exposed X-Ray
- If you cannot see the vertebrae, this is underexposed and means you could miss key pathology
State what you believe to be obvious pathology if you can and then say you will work through it systematically.
B- Bowel
Now that you have confirmed patient details and commented on the film quality, you can start going through the Abdominal X-Ray systematically.
The first part of the acronym (B) focuses on the bowels. This involves looking at the large and small bowels.
Small Bowel
When looking at the small bowel, the main feature we are trying to assess if there is an obstruction. Small bowel can be discerned from large bowel by its location (more central) and it also has valvulae coniventes – these are folds that cross the whole diameter of the lumen of the small bowel.
Small bowel should be more or less invisible in a normal abdominal X-Ray. If it is more visible then this suggests it might be dilated due to an obstruction. The cut-off is 3cm. Dilation more than 3cm shows a small bowel obstruction.
Large Bowel
When looking at the large bowel, the main feature we are trying to assess if there is an obstruction. Small bowel can be discerned from large bowel by its location (more peripheral) and it also has haustra – these are folds that do not cross the whole diameter of the lumen .
There are various features we look at for the large bowel:
- Large bowel obstruction – This is dilation more than 6cm or 9cm for th caecum and sigmoid.
- Faecal loading – faeces gives a mottled appearance in AXR and can indicate constipation.
- Loss of haustra markings – this is a sign of large bowel inflammation. Seen in conditions like ulcerative colitis and C dif. If this is combined with dilation then it suggests toxic megacolon, which is a surgica emergency.
- Pneumoperitoneum – Normally only inner wall is visible on AXR. If there is perforation, air collects on both sides leading to the double wall sign (Riggler) which is suggestive of air in the peritoneal cavity.
O – Other Organs
Whilst the bowels takes up most of the focus in AXR analysis, remember that the abdomen is fully of other organs.
After scanning through the bowels, we recommend a screen of the other organs working superiorly to inferiorly to detect any pathology. This will ensure you are not missing anything important.
Lungs Bases
- Check for lung base consolidation – can give apparent abdominal pain
Liver and Gallbladder
Liver
- Check for masses, cysts
Gallbladder
- Check for cholecystectomy clips
- Check for calcifications = gallstones
Stomach
- This is seen in the left upper quadrant.
- Check for air bubble – this is a normal finding
Urinary System
Kidney
- Check for calcifications
- Check for masses
Psoas muscle
- Check for abscesses
Ureters
- These run down tips of spinal processes and pelvic brim
- Check for calcifications
Bladder
- Check for urinary retention
- Masses in pelvis may suggest pelvic tumours
B – Bones
An abdominal X-Ray is not the most sensitive investigation for looking at abdominal structures.
However, even on an AXR, you will be able to spot gross abnormalities associated with the bones, especially the vertebral column.
Therefore, after looking at the bowels and the other organs, to complete your systematic analysis, make sure you comment on the bones to avoid missing key pathology.
Vertebrae
The vertrebra should be clearly visible on an Abdominal X-ray, especially if there are no other pathological signs. Therefore, it is important that you comment on the spinal column, looking for the following features:
- Fractures, lytic lesions
- Ankolysing Spondylosis – this is seen by fusion of the vertebra leading to a “bamboo spine”
Sacrum and Coccyx
Sacrum
- Fractures
- SI joint fusion = This is seen in anjylosing spondylitis
Coccyx
- Fractures
Pelvis
Though not the highest priority of an abdominal X-Ray, you may be able to spot the following:
- Pubic rami fractures
- Ischial fractures
Ribs
On an AXR, it is possible to detect fractures of the lower ribs. Have a glance to see if you can spot any.
Femur
Look out for the following:
- Neck of femur fracture
- Hip dislocation
- Osteoarthritis of the hip joint
C- Calcifications and Other
Before you conclude your interpretation of an abdominal X-Ray, remember there are still other things that you can detect.
This includes calcifications, which show up as white and other objects like foreign bodies or iatrogenic materials.
Calcifications
Look for calcifications in the following areas as these may represent particular pathologies:
Right Upper Quadrant
- Gallstones
Right/ Left Flank (kidneys)
- Staghorn (renal) calculi
Paravertebral
- Abdominal aorta calcification
Epigastric area
- Chronic pancreatitis (shown by calcification of the pancreas)
Other Lines/Tubes/Opacification
The following features are also detectable on abdominal X-Rays.
- Uretertic stents
- NG tube
- Surgical clips
- Piercings
- Foreign bodies in the bowel
Review Areas
Before you end your analysis, it is recommended to review 4 areas. This is because there are 4 of the most common places where pathology is missed in a Chest X-Ray. This is often because changes here may be very subtle, and you will easily miss them unless you speficially concentrate on these areas. The 4 areas are.
• Small and large bowel
• Pelvic Ramus
• Sacro-iliac joint and hip joint
• Right Upper quadrant
Example
Now that we know how to systematically go through a AXR, let’s have a look at how we would interpret the AXR we saw at the beginning.
AXR Interpretation
D – This is an Abdominal X-Ray taken on ….., of the following patient….. Is there a previous AXR to compare to
R – Commenting first on the quality, it is not rotated, there is adequate field of view, the projection is anterior-posterior it is adequately exposed as I can see the vertebral bodies clearly
On initial inspection, there is no obvious pathology, but I will proceed to go through it systematically.
B – Looking at the film, the small bowel is not visible. The ascending and transverse colon are visible with some air in the large bowel, but it is not distended. There is evidence of some faecal loading in the rectum.
O – Looking at the other organs, there is no basal lung consolidation. No hepatobiliary abnormality. The urinary system looks normal and no evidence of a psoas muscle abscess.
B – There are no fractures to the bones. There is a lateral curvature of the spine but the vertebrae appear normal. There is normal spacing of the sacroliliac and hip joints.
C – There are no other calcifications or foreign bodies.
In summary this AXR shows some faecal loading in the rectum and a lateral curvature of the spine. It would be useful to see if there is previous to compare to in order to see if this is a new finding or chronic.
Check out the following pages to see more examples of common pathologies seen on Abdominal X-Ray.
Sources
Image 1: © Nevit Dilmen, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
Image 2: Bickle, I. Faecal loading. Case study, Radiopaedia.org. (accessed on 11 Oct 2022) https://doi.org/10.53347/rID-44486
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