The 'Mercedes-Benz sign' on CT abdomen (three low-density stellate lines within a hyperdense gallstone) indicates:

• A Cholesterol gallstone with radial clefts — NOT suitable for oral dissolution therapy
• B Calcified (calcium carbonate) gallstone — difficult to dissolve
• C Gallstone with central pigment nucleus — mixed composition
• D Gas-containing gallstone — suitable for lithotripsy ✓

Explanation

The Mercedes-Benz or 'Star of David' sign on CT describes a low-density triradiate crack pattern within a gallstone, caused by nitrogen gas filling fissures in a cholesterol stone. This indicates a gas-containing (nitrogen) stone that is generally suitable for shock-wave lithotripsy (ESWL) because the gas clefts suggest it is pure cholesterol and will fragment. It is NOT a contraindication — in fact it predicts good response. Calcified (calcium-rich) stones are radio-opaque uniformly and respond poorly to dissolution.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.