Acute cholecystitis is an inflammatory condition of the gallbladder typically incited by mechanical obstruction. Accurate diagnosis of this common clinical condition is challenging due to variable imaging appearances as well as overlapping clinical manifestations with biliary colic, acute hepatitis, pancreatitis, and cholangiopathies. In acute cholecystitis, increased dilatation and high intraluminal pressures lead to gallbladder inflammation and may progress to gangrenous changes, focal wall necrosis, and subsequent perforation. In acute calculous cholecystitis, gallstones are the cause of obstruction and are often impacted in the gallbladder neck or cystic duct, leading to gallbladder inflammation. In acalculous cholecystitis, patients are typically critically ill, often with hypotensive episodes and prolonged gallbladder stasis, which lead to obstruction, gallbladder ischemia, and inflammation. Helpful sonographic findings of acute cholecystitis include a dilated gallbladder; increased intraluminal pressures in the gallbladder, resulting in a bulging fundus (tensile fundus sign); intraluminal sludge in the setting of right upper quadrant pain; wall hyperemia, which may be quantified by elevated cystic artery velocities or hepatic artery velocities; mucosal ischemic changes, characterized by loss of mucosal echogenicity; pericholecystic inflammation, characterized by hyperechoic pericholecystic fat; and mucosal discontinuity. Extruded complex fluid next to a wall defect is definitive for gallbladder wall perforation, and further evaluation with CT or MRI allows evaluation of the full extent of perforation and other potential complications. The sonographic Murphy sign, while helpful if positive, is relatively insensitive for accurate diagnosis of acute cholecystitis. Thus, overreliance on the sonographic Murphy sign results in surprisingly low diagnostic accuracy in practice.
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