Pigment stones
Contents
Pigment stones are type of Gallstones
Appearance
Bilirubin (“pigment”, “black pigment”) stones are small, dark
Usually numerous.
Composition
- Bilirubin – insoluble bilirubin pigment polymer
- Calcium (calcium phosphate) salts- that are found in bile.
They contain less than 20% of cholesterol (or 30%, according to the Japanese classification system).
Between 2% and 30% of stones are bilirubin stones
Black and brown pigment gallstones are morphologically, compositionally, and clinically distinct.
Black stones
Black stones form primarily in the – gallbladder in sterile bile and are associated with advanced age, chronic hemolysis, alcoholism, cirrhosis, pancreatitis, and total parenteral nutrition.
Brown stones
Brown stones form not only within the gallbladder but also within the intrahepatic and extrahepatic ducts; they are uniformly infected with enteric bacteria and are usually associated with ascending cholangitis.
Pathogenesis of black stones
High heme turnover- chronic hemolysis or cirrhosis,
Unconjugated bilirubin – present in bile at higher than normal concentrations.
Calcium bilirubinate crystallize from the solution and form stones.
Oxidations cause the bilirubin precipitates to take on a jet-black color, and stones formed in this manner are termed black pigment gallstones.
Pathogenesis of black stones is related to nonbacterial, nonenzymatic hydrolysis of bilirubin conjugates. At the pH of bile, this results in two monohydrogenated bilirubin anions that precipitate with calcium ions.
Pathogenesis of Brown pigment stones
Bacteria hydrolyze lecithin to release fatty acids that bind calcium and precipitate from the solution.
The resulting concretions have a claylike consistency and are termed brown pigment stones.
Unlike cholesterol or black pigment gallstones, which form almost exclusively in the gallbladder, brown pigment gallstones often form de novo in the bile ducts.
Brown pigment stones are formed in bile infected with enteric bacteria that elaborate hydrolytic enzymes: β-glucuronidase, phospholipase A, and conjugated bile acid hydrolase. The resulting anions of bilirubin and fatty acids form insoluble calcium salts.
Gallstones – Pigment stones – Table
| Pigment stones | Black pigment stones | Brown pigment stones | |
| 1 | Common Situation | High heme turnover | Infection |
| 2 | Stone Formation | Calcium bilirubinate crystallize from the solution and form stones | Bacteria hydrolyze lecithin to release fatty acids that bind calcium and precipitate from the solution. |
| 3 | Consistency | Harder | claylike consistency |
| 4 | Mechanism | Pathogenesis of black stones is related to nonbacterial, nonenzymatic hydrolysis of bilirubin conjugates. | Formed in bile infected with enteric bacteria that elaborate hydrolytic enzymes |
| 5 | Site of formation | Form almost exclusively in the gallbladder | Often form in the bile ducts |
