emphysematous cholecystitis

**Definition:** Acute cholecystitis complicated by gas-forming organisms, with gas in the gallbladder lumen, wall, or pericholecystic space. About 20–50% of cases are acalculous, which is a much higher share than in ordinary cholecystitis.

**Pathophysiology:** The leading theory is vascular compromise (cystic artery ischemia) followed by secondary bacterial invasion. Cystic duct obstruction, atherosclerosis, and diabetic microangiopathy all contribute to this. Ischemic, hypoxic tissue favors anaerobes and facultative anaerobes, which ferment tissue substrates and produce gas. - Organisms: Clostridium perfringens (about 50%), E. coli, Klebsiella, other anaerobes, and Staphylococcus, Streptococcus, and Pseudomonas species.

**Risk factors:** - Diabetes mellitus (about 20–50% of cases; the key association) - Male sex (male:female about 3:1) and age 50–70 - Atherosclerotic vascular disease - Critical illness (ICU, burns, trauma, prolonged TPN, or fasting) in acalculous cases - Immunosuppression

**Clinical presentation:** Symptoms resemble acute cholecystitis: RUQ pain, fever, nausea and vomiting, leukocytosis, and possibly a positive Murphy sign. Diabetics may have blunted or atypical findings, so the diagnosis is often delayed. Crepitus may occur in severe disease. Complications include gangrene (about 75%), perforation (about 15–20%, versus about 2% in ordinary cholecystitis), sepsis, and abscess. Mortality is about 15–25%, versus about 4% in uncomplicated cholecystitis.

**Diagnosis:** - Plain film: gas in the gallbladder, which may show an air-fluid level. This is seen late and is often missed. - Ultrasound: a hyperechoic focus with "dirty" posterior shadowing, which can be mistaken for a porcelain gallbladder or bowel gas. - CT is the most sensitive and specific test. It shows gas in the lumen or wall and can detect perforation. - Differential for gas in the biliary system: emphysematous cholecystitis, gallstone ileus or a cholecystoenteric fistula (pneumobilia), post-ERCP or sphincterotomy, and a biliary-enteric anastomosis. Pneumobilia is gas in the bile ducts. In emphysematous cholecystitis the gas is in the gallbladder wall or lumen.

**Management:** - Resuscitation with IV fluids. - Broad-spectrum antibiotics covering anaerobes and gram-negative rods, such as piperacillin-tazobactam or a carbapenem. Add metronidazole if the regimen lacks anaerobic coverage. Cover Clostridium (penicillin or clindamycin). - Emergent or urgent cholecystectomy is the definitive treatment. - Percutaneous cholecystostomy is an option for patients too unstable for surgery, as a bridge to later surgery.

**Boards pearls:** - Think of an elderly diabetic man with RUQ pain and gas on imaging. - Gas in the gallbladder wall on imaging is the classic finding. - Clostridium perfringens is the classic organism. - It has a higher rate of gangrene and perforation than standard cholecystitis. - The treatment is urgent surgery plus antibiotics. - Do not confuse it with emphysematous pyelonephritis (another gas-forming infection in diabetics, caused by E. coli or Klebsiella) or with porcelain gallbladder (calcified wall, associated with gallbladder cancer).