What causes gas gallstones?
As part of the crystallization process, there is a predilection for central fissure formation that radiates peripherally, leaving a void to be filled by either gas (likely nitrogen) or bile; roughly 50% of gallstones contain some amount of fissuring.
What causes rim-calcified gallstones?
Increased biliary calcium concentrations due to chronic CBD obstruction and low-grade GB wall inflammation lead to impaired H+ secretion by the GB wall and subsequent increase in calcium efflux into the GB lumen. High biliary calcium concentration is common in pigment stones; only about 10-20% of gallstones have calcium concentrations significant enough to be visualized on plain films [2].
Several multifaceted rim-calcified gallstones of varying sizes are present within the gallbladder.
The common bile duct diameter is at the upper limits of normal. No gallstones are seen within the common bile duct.
There is a gas-filled stone near the gallbladder neck revealing a “Mercedes-Benz” sign (arrow).