Gallbladder sludge: what is its clinical significance? Shaffer EA(1). (1)Faculty of Medicine, Department of Medicine, Foothills Hospital, Room C210, 1403 29th Street NW, Calgary, AB T2N 2T9, Canada. Biliary sludge is a mixture of particulate solids that have precipitated from bile. Such sediment consists of cholesterol crystals, calcium bilirubinate pigment, and other calcium salts. Sludge is usually detected on transabdominal ultrasonography.