Background: Cholecystitis is defined as inflammation of the gallbladder that occurs most commonly because of an obstruction of the cystic duct from cholelithiasis. Ninety percent of cases involve stones in the cystic duct (ie, calculous cholecystitis), with the other 10% representing acalculous cholecystitis. Although bile cultures are positive for bacteria in 50-75% of cases, bacterial proliferation may be a result of cholecystitis and not the precipitating factor. Risk factors for cholecystitis mirror those for cholelithiasis and include increasing age, female sex, certain ethnic groups, obesity or rapid weight loss, drugs, and pregnancy.
Acalculous cholecystitis is related to conditions associated with biliary stasis, including debilitation, major surgery, severe trauma, sepsis, long-term total parenteral nutrition (TPN), and prolonged fasting. Other causes of acalculous cholecystitis include cardiac events; sickle cell disease; Salmonella infections; diabetes mellitus; and cytomegalovirus, cryptosporidiosis, or microsporidiosis infections in patients with AIDS.
Pathophysiology: Acute calculous cholecystitis is caused by obstruction of the cystic duct, leading to distention of the gallbladder. As the gallbladder becomes distended, blood flow and lymphatic drainage are compromised, leading to mucosal ischemia and necrosis. A study by Cullen et al (2000) demonstrated the ability of endotoxin to cause necrosis, hemorrhage, areas of fibrin deposition, and extensive mucosal loss, consistent with an acute ischemic insult. Endotoxin also abolished the contractile response to cholecystokinin (CCK), leading to gallbladder stasis.
Although the exact mechanism of acalculous cholecystitis is unclear, a couple of theories exist. Injury may be the result of retained concentrated bile, an extremely noxious substance. In the presence of prolonged fasting, the gallbladder never receives a CCK stimulus to empty; thus, the concentrated bile remains stagnant in the lumen.
In the US: An estimated 10-20% of Americans have gallstones, and as many as one third of these people develop acute cholecystitis. Cholecystectomy for either recurrent biliary colic or acute cholecystitis is the most common major surgical procedure performed by general surgeons, resulting in approximately 500,000 operations annually.
Most patients with acute cholecystitis have a complete remission within 1-4 days. However, 25-30% of patients either require surgery or develop some complication.
Patients with acalculous cholecystitis have a mortality rate ranging from 10-50%, which far exceeds the expected 4% mortality rate observed in patients with calculous cholecystitis. Emphysematous cholecystitis has a mortality rate approaching 15%.
Perforation occurs in 10-15% of cases.
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