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Gallbladder Pathology Online

Pathology of the Pigment Gallstones

Dr  Sampurna Roy  MD


Pigment gallstones are of two major types, black and earthy brown, each consisting of calcium salts of bilirubin and other anions, along with an unmeasured residue that is largely mucin glycoproteins.

Visit: "Mixed" stones ; Cholesterol stone

Pigment stones comprise about 15% of the total gallstone formed in the gallbladder.

The black and brown stones have distinctive features:

Black Pigment Stones:

Black stones range in shape and size from irregular, mulberry or coral-like iridescent concretions of less than 1 cm across.

Often they are simply soft putty-like masses.

On section all pigment stones seem to be amorphous and glassy.

Black stones contain calcium bilirubinate, bilirubin polymers, calcium salts and mucin.

The incidence black stones is increased in elderly and malnourished patients.

There is usually no correlations with gender, ethnicity, or obesity.

Chronic hemolysis, as in sickle cell anemia and thalassemia, predispose to the development of black pigment stones.

Cirrhosis is also associated with a high incidence of black stones.

According some authors both cirrhosis and alcoholism predispose to pigment gallstone formation and that the effect of alcoholism may occur independent of cirrhosis. It was suggested that the apparent association of cirrhosis with pigment stones may, in fact, result from a direct effect of long-term ethanol ingestion on red blood cells, liver, or bile.

In most cases no predisposing cause for the formation of black pigment stones is evident.

The pathogenesis of black pigment stones is related to an increased concentration of unconjugated bilirubin in the bile.  Pigment gallstone disease.

Unconjugated bilirubin is insoluble in bile. Normally it is present in only trace amounts. When increased amounts are secreted by the hepatocytes, the unconjugated bilirubin precipitates as calcium bilirubinate, probably around a nidus of mucinous glycoproteins. The patients without known predisposing factors who develop black pigment stones often have increased concentrations of unconjugated bilirubin in the bile.

Brown pigment stones:

Brown pigment stones contain principally calcium bilirubinate mixed with cholesterol and calcium soaps of fatty acids.

Macroscopically these are usually spongy and laminated.

In contrast to the other types of gallstones, brown pigment stones are found more frequently in the intrahepatic and extrahepatic bile ducts than in the gallbladder.

These stones are almost always associated with bacterial cholangitis. Example: Escherichia coli which is the predominant organism. Brown stones are also associated with other infectious diseases like Ascaris lumbricoides, Clonorchis sinensis, and helminths that may invade the biliary tract.

In some cases these stones are found only in patients with mechanical obstruction to the flow of bile, as in sclerosing cholangitis or as a result of a catheter in the common bile duct after common bile duct surgery.

The pathogenesis of brown pigment stones is also related to an increased concentration of unconjugated bilirubin in the bile. 

Cholecystectomy is usually curative in black pigment stone disease, whereas stones often recur after cholecystectomy for brown stone disease.


Further reading:

The role of bacteria in pigment gallstone disease.

The etiology of pigment gallstones.

Pigment gallstone disease.

Pigment gallstone pathogenesis: slime production by biliary bacteria

Black and brown pigment gallstones differ in microstructure

Inhibition of cholesterol crystallization under bilirubin deconjugation: partial characterization of mechanisms wherby infected bile accelerates pigment stone formation. 

Cirrhosis and alcoholism as pathogenetic factors in pigment gallstone formation











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