Figure 3a. Emphysematous cholecystitis in a 49-year-old diabetic man with a 2-day history of substernal pain and fever. (a) Transverse US image through the gallbladder fossa demonstrates a curvilinear collection of high-amplitude echoes (arrowheads) with posterior dirty shadowing (arrow). (b) Longitudinal US image shows a diffusely echogenic gallbladder wall secondary to intramural gas (arrowheads). (c) US image reveals multiple tiny echogenic reflectors within the gallbladder lumen (arrows) corresponding to gas bubbles arising from the dependent wall (champagne sign).