Presentation
CT requested upon urinary bladder tumor.
Patient Data
Age: 70 years
Gender: Female
From the case:
Mercedes-Benz sign of gallstones
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An accidental finding of multiple, air-containing gallstones.
In the center of the gallstones the density is between -150 HU and -100 HU.
Case Discussion
Ultrasound is still the first line imaging tool for diagnosing gallstones.
Gas or fluid containing gallstones are relatively rare findings on abdominal CT. Characteristic finding is the low density, star shaped center within a gallstone, producing a triradiate pattern, similar to Mercedes-Benz automobile sign.
CT can reveal air inside the stones:
- stones with central density under -100 HU are considered as gas containing gallstones
- stones with central density between 0 and -100 HU can contain mixed gas and fluid
As a pathological background, degenerating stones can collect nitrogen gas in central fissures