Which of the following conditions is characterized by an enlarged gallbladder?

An enlarged gallbladder is most commonly associated with cholecystitis, which is the inflammation of the gallbladder. Cholecystitis typically occurs when a gallstone blocks the cystic duct, leading to a backup of bile and increased pressure within the gallbladder. This condition can be acute or chronic, and in either case, swelling of the gallbladder is a notable clinical feature. The inflammation often causes the gallbladder to become enlarged and may present with symptoms such as abdominal pain, nausea, and fever.

In contrast, while cholelithiasis refers to the presence of gallstones, it does not necessarily result in gallbladder enlargement unless there is an associated acute cholecystitis. Diverticulitis involves the inflammation of diverticula in the colon and is not related to gallbladder size. Intussusception refers to a condition in which part of the intestine slides into an adjacent segment, also unrelated to gallbladder enlargement. Thus, among the conditions listed, cholecystitis is specifically characterized by an enlarged gallbladder due to the underlying inflammation.