X-Ray Teasers



A 40yo man presents with ankle pain after a fall

Describe and interpret the Xray:


This is a classic case that could easily come up in the SCEs, and teaches us a valuable lesson about interpreting Xrays.  This is a plain AP Xray of the left ankle. There is possibly a subtle transverse fracture of the fibula approximately 10cm above the joint.  There is a cortical irregularity of the medial malleolus which may represent an undisplaced fracture, and the ankle mortice looks disrupted, with widening of the medial joint space.

So what do you do?


Here’s the lateral:


Which shows the now obvious posterior malleolar fracture, and that “subtle” fibular fracture is actually a nasty spiral fracture

…and the oblique view…


which shows a grossly disrupted ankle that clearly needs an ORIF.

And yes, these Xrays are all from the same patient (we didn’t make this up!).


In the SCE. if you are shown an Xray that is usually part of a series, eg ankle, hip, shoulder, C-spine, then make sure you ask for ALL of the available views!




An 88 year old woman presents with upper abdominal pain and vomiting. (She has never had surgery before). Describe and interpret her CT scan. (This is from a real patient seen last night!)

image 1



This is a single axial slice of a CT abdoment with oral and IV contrast. The most striking abnormality is gas in the liver.  This can either be in the biliary tree, or in the portal veins. The more centralised location of the gas in this case suggests that it is in the biliary system. This is called “Pneumobilia”.  There is a long list of causes of pneumobilia, if you don’t know them see our links at the end of this answer.  We’ll give you some clues for this case…

Here is another slice from same patient’s CT:

image 2


This shows distended loops of small bowel with air-fluid levels consistent with a small bowel obstruction.

Got any ideas as to what would cause pneumobilia and a small bowel obstruction?


Here’s another image from her CT:

image 3


There is a 3cm diameter irregularly calcified mass in the right iliac fossa, within the lumen of the small bowel.  This is a GALLSTONE!


The patient has had a spontaneous biliary-enteric fistula (which has allowed gas to enter the biliary system), and has a passed a gallstone into her small bowel, causing a gallstone ilieus, or small bowel obstruction.



Learn your differential diagnoses, and when you see two seemingly unrelated things on an image, try and find where your list of differentials intersect:

Pneumobilia DDx: (see this link for a nice succinct differential). In a virgin abdomen, something has to have leaked or perforated to allow the gas into the biliary system. In this case it was the biliary-enteric fistula.

Small Bowel Obstruction DDx: Adhesions, Adhesions, Adhesions, Hernia, Crohn’s, Intussusception, Gallstone, Ileus

Always ask for more images (in the SCE), as this will nearly always help you find the answer (if it isn’t obvious on the first image). You might not get a second image, but if you can’t see the answer on the first image you are shown, you won’t lose anything by asking.


Here’s a link to a differential diagnosis for Portal Venous Gas, another ominous CT sign.  It has a simple explanation & some images that will help you differentiate biliary from portal venous gas.


Here’s a couple of images showing penumobilia, visible on a plain abdominal x-ray. (blue circles) Subtle but quite important if you notice it!



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