Hi, Gall bladder (GB) sludge is a very frequent finding on ultrasonography. Normally the GB will appear to be one smooth fluid filled sac (esp if the scan was done after an over night fast). This is because, bile being liquid allows the ultrasound waves to pass through easily. If there is a stone, it will reflect some of the waves back and this will make it visible on the ultrasound. GB sludge is a term used when the bile, instead of appearing as a single smooth layer in the GB appears as two different layers. This happens when the bile in the GB has two different densities, so one sinks in the other. This heavier sludge usually consists of crystals made up of cholesterol and pigments. This usually occurs after a pregnancy, rapid weight loss and prolonged fasting. The sludge usually does not cause any symptoms, but has been blamed rarely for biliary colic, pancreatitis and rarely cholecystitis. But more commonly the sludge usually disappears on its own and rarely requires any treatment. Hope this helped and thanks for the question.