The gallbladder is located between the intestines and the liver. It stores bile from the liver until it’s time to release it into the intestines to aid in digestion. If the gallbladder doesn’t empty completely, particles in the bile, like cholesterol or calcium salts, can thicken from staying in the gallbladder for too long. They eventually become biliary sludge, which is commonly referred to as gallbladder sludge.