Gallstone disease: classification

Gallstones are classified:

• Localization: in the gallbladder; in the common bile duct; in the hepatic ducts.
• By the number of stones: single; multiple.
• By composition:
  • cholesterol - contain mainly cholesterol, have a round or oval shape, a lamellar structure, diameter from 4-5 to 12-15 mm; typical localization is a gallbladder;
  • pigment (bilirubin) are characterized by small sizes, usually multiple; rigid, brittle, perfectly homogeneous, located both in the gall bladder and in the bile ducts;

Pigmental stones are called that contain less than 30% cholesterol. There are black and brown pigmented stones.

• Black pigmented stones consist mainly of black pigment, phosphate and calcium carbonate without cholesterol. The mechanism of their formation is not completely clear, although the role of bile supersaturation with unconjugated bilirubin, changes in pH and calcium level in the bile, and excessive production of the organic matrix (glycoprotein) is known. Black pigmented stones account for 20-30% of the total number of gallstones and are more common in elderly patients. They can migrate to the bile ducts. The formation of black pigmented stones is characteristic for chronic hemolysis, for example for hereditary spherocytic or sickle cell anemia, artificial heart valves and vascular prostheses, all forms of liver cirrhosis, especially alcohol. The drug dissolution of black pigmented stones is at the stage of experimental development.
• Brown pigmented stones contain calcium bilirubin, polymerized to a lesser degree than in black pigmented stones, as well as palmitate and calcium stearate and cholesterol. Brown pigmented stones are formed in the bile ducts against the background of stasis of bile and infection, in the gallbladder are rare and usually roentgenogenous. Their formation is associated with the decomposition of diglucuronide bilirubin with beta-glucuronidase bacteria, as a result of which precipitated insoluble unconjugated bilirubinate. Brown pigmented stones are formed above the strictures (with sclerosing cholangitis) or in the enlarged sections of the biliary tract (with Caroli's disease). The formation of brown pigmented stones in the absence of diseases of bile ducts is associated with juxtapapillary diverticula of the duodenum. Bacterial inclusions are found in more than 90% of cases. In eastern countries, brown pigmented stones complicate the invasion of the biliary tract Clonorchis sinensis and Ascaris lumbricoides and are often located intrahepatically. From the common bile duct they are removed with the help of endoscopic papillosphincterotomy, and from the intrahepatic ducts - by lithotripsy, percutaneous drainage, or surgically.
• Mixed (are found most often) - more often multiple, the most diverse form; they include cholesterol, bilirubin, bile acids, proteins, glycoproteins, various salts, trace elements.

In Western countries cholesterol stones are more common. Despite the fact that the main component of cholesterol stones is cholesterol (51-99%), in them, as in other types of stones, components such as carbonate, phosphate, bilirubin and calcium palmitate, phospholipids, glycoproteins and mucopolysaccharides are found in various proportions. According to crystallography, cholesterol in gallstones is present in the form of monohydrate and in anhydrous form. The nature of the core of the stone is not established. The role of pigments, glycoprotein or amorphous material was assumed.

It remains unclear why the water insoluble cholesterol is retained in bile in a dissolved state and what mechanisms lead to its precipitation and the formation of gallstones.

[1], [2], [3], [4], [5], [6], [7], [8]