Microscopic gallstones: A mixture of microscopic particulate matter in bile, also called biliary sludge, that occurs when particles of material precipitate from bile. (Bile is the fluid that is made by the liver. It is stored in the gallbladder until after a meal when it passes out of the gallbladder and through the common bile duct into the intestine to help digest fat in the meal.)
The composition of biliary sludge varies. The most common particulate components of biliary sludge are cholesterol crystals and calcium salts.
Biliary sludge has been associated with certain conditions including rapid weight loss, fasting, pregnancy, medications (ceftriaxone, octreotide), and bone marrow or solid organ transplantation although it most commonly occurs in individuals with no identifiable condition.
Biliary sludge can be looked upon as a condition of microscopic gallstones, although it is not clear at what size the particles in biliary sludge should be considered gallstones. More important than the differentiation by size is whether or not there are symptoms since symptoms of biliary sludge or gallstones are treated similarly.
Biliary sludge usually causes no symptoms and may appear and disappear over time. Biliary sludge, however, may cause intermittent symptoms and, on occasion the particles may grow in size and become larger gallstones.
The most common symptom of biliary sludge -- when it causes symptoms -- is pain in the abdomen often associated with nausea and vomiting. This occurs when the particles obstruct the ducts leading from the gallbladder to the intestine.
Biliary sludge also may cause more serious complications, including inflammation of the pancreas (pancreatitis), and inflammation of the gallbladder (cholecystitis).
Biliary sludge can be detected with ultrasound of the abdomen or by directly examining bile contents under a microscope (bile microscopy).
If patients with biliary sludge develop symptoms or complications, gallbladder removal (cholecystectomy) is performed as treatment. Since sludge usually does not cause symptoms, it should be strongly suspected that a patients symptoms are due to sludge before the gallbladder is removed.