History: abdominal distention
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Findings: Large air filled “coffee bean” shaped structure in the mid-abdomen
Answer: Sigmoid volvulus
The sigmoid colon often has a small upside-down U-loop. So if those two ends happen to start twisting (I use the analogy of a "twist-tie" on a loaf of bread), it creates not just a single obstruction point, but TWO!
- Proximal obstruction blocks the colon proximal to the twist
- Distal obstruction blocks the segment between the twists yielding a "closed loop" obstruction which is at high risk of rupture
Sometimes these can be a little tricky (even on CT) and commonly they can get confused with a sigmoid volvulus.
- Sigmoid voluvus obstruction is at the sigmoid colon so you typically have dilated descending colon, transverse colon, etc. proximally but no gas in the rectum.
- Cecal volvulus obstruction is at the cecum so your colon should be empty as your body tries to push through the mechanical obstruction.
Plain film signs you can look for are:
- Coffee bean sign: dilated gas filled (often ahaustral) sigmoid colon resembling a coffee bean - as seen here
- absent rectal gas and dilated proximal-mid colon (as described above)
- Frimann-Dahl sign: similar to coffee bean sign but you see classically 3 seperated haustra converging towards the point of obstruction
- Northern exposure sign: where the apex of the sigmoid loop is above the transverse colon. (not a big fan of this, especially if there is a redundant transverse colon)
- typically the sigmoid volvulus extends up into the right upper quadrant (liver overlap sign) versus cecal volvulus which tends to go into the left upper quadrant