Cholecystitis

Cholecystitis is inflammation of the gallbladder, most often caused by a blockage in the cystic duct that traps bile inside. About 95% of cases are calculous, caused by gallstones. Critically ill patients may develop acalculous cholecystitis due to bile stasis and reduced blood flow. The trapped bile increases intraluminal pressure, restricting venous outflow and impairing lymphatic drainage, leading to tissue swelling and hypoxia.

As pressure builds in the gallbladder, oxygen delivery declines and ischemia develops, particularly in the fundus, the least well-perfused region. This oxygen deprivation damages the mucosal lining and triggers an inflammatory response. Neutrophils infiltrate the gallbladder wall, and retained bile salts further irritate tissue. Prolonged ischemia can lead to necrosis or perforation if untreated.

Risk factors include obesity, rapid weight loss, high-fat diets, pregnancy, oral contraceptive use, long-term fasting, mechanical ventilation, and ICU admission following major trauma. Hemolytic disorders also increase risk. Critically ill patients, particularly those on total parenteral nutrition or with sepsis, are susceptible to acalculous cholecystitis, which occurs without gallstones.

Pain typically occurs in the right upper quadrant below the right costal margin, often radiating to the right scapular region or posterior shoulder. Onset usually follows high-fat meals by 30 minutes to several hours. Associated symptoms include nausea, vomiting, fever, positive Murphy's sign, leukocytosis, and elevated liver enzymes.

A gallstone can migrate and block the pancreatic duct at the ampulla of Vater, causing acute pancreatitis. This complication occurs when stones escape the gallbladder and obstruct the shared ductal opening. Understanding this relationship is important for recognizing that cholecystitis complications may extend beyond the gallbladder itself.

Calculous cholecystitis accounts for 95% of cases and is caused by gallstones blocking the cystic duct. Acalculous cholecystitis occurs without gallstones, primarily in critically ill patients experiencing bile stasis and ischemia. It commonly develops after major surgeries like coronary artery bypass grafting, especially in patients on total parenteral nutrition, with sepsis, or following trauma.

Yes, secondary bacterial infection may develop as cholecystitis progresses. Common causative organisms include Escherichia coli and Klebsiella species. The damaged mucosal lining from ischemia and inflammation allows bacteria to colonize the gallbladder wall, potentially worsening the condition and increasing risk of serious complications.