A 60-year-old diabetic man is admitted to the hospital with a diagnosis of acute cholecystitis. The WBC count is 28,000, and a plain film of the abdomen and CT scan show evidence of intramural gas in the gallbladder. What is the most likely diagnosis?
Emphysematous gallbladder Acalculous cholecystitis Cholangiohepatitis Sclerosing cholangitis