Is a gallbladder sludge considered a gallbladder disease?

Yes if there's pain.: Pain after eating, anywhere in the upper abdomen, especially with fatty foods, may be cholecystitis. This is true if stones are present, called "cholelithiasis with cholecystitis." sometimes when the gall bladder ultrasound is "normal", i.e. There are no stones, the gall bladder doesn't empty properly (seen on cck hida). This can also be true with sludge. In all cases, surgery relieves the pain.