You have a gallbladder that is blocked at the neck. The blockage is basically a gallstone and the gallbladder is full of sludge. Sludge is name used to describe a solid mass of bile that can vary in size from grains of sand to the size of the gallbladder itself. Because of the stone and sludge the gallbladder is filling with watery fluid (hydrops) as has become swollen, giving pain.