Gross and microscopic features of cholesterol and pigment stones 2nd mbbs pathology
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cholesterol pigment gallstones gross microscopic morphology pathology
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Cholesterol and pigment gallstones: gross and microscopic features
1. Cholesterol stones
Gross features
- Form only in the gallbladder.
- Usually multiple, though occasionally a single large stone may fill the fundus.
- Typically round or ovoid.
- Pure cholesterol stones are:
- Pale yellow
- Hard
- Finely granular externally
- On cut section, show a glistening radiating crystalline pattern.
- Stones containing more calcium salts and bilirubin become grey-white, greenish, brown, or black, and may be laminated.
- Multiple stones may become faceted because they press against one another.
- Usually radiolucent, but 10% to 20% contain enough calcium carbonate to be radiopaque.
Microscopic features
- Composed predominantly of cholesterol monohydrate crystals, constituting more than 50% of the stone.
- Crystals are typically flat, rectangular plates with notched corners.
- On polarised light, cholesterol crystals are birefringent.
- The crystals are embedded in a matrix of mucin glycoprotein, with variable calcium salts and bilirubin pigment.
Source: Robbins, Cotran & Kumar Pathologic Basis of Disease, Cholelithiasis morphology.
2. Pigment stones
These are composed mainly of calcium salts of unconjugated bilirubin. They are of two types: black and brown.
| Feature | Black pigment stones | Brown pigment stones |
|---|---|---|
| Usual location | Gallbladder, with sterile bile | Large intrahepatic or extrahepatic bile ducts |
| Association | Chronic hemolysis, cirrhosis, ineffective erythropoiesis | Biliary infection and stasis, often with parasites |
| Gross appearance | Black, small, brittle/friable, often numerous | Brown, soft, greasy or soap-like |
| Shape | Spiculated, irregular, molded | Usually rounded and laminated |
| Radiology | Often radiopaque due to calcium salts | Usually radiolucent |
Gross features
- Colour ranges from brown to black.
- Black stones:
- Small, usually less than 1.5 cm
- Numerous
- Brittle and friable
- Irregular, spiculated, or molded contours
- Often radiopaque.
- Brown stones:
- Soft and laminated
- Greasy or soap-like consistency
- Usually form within infected bile ducts
- Usually radiolucent.
Microscopic features
- Predominantly contain calcium bilirubinate, that is, insoluble calcium salts of unconjugated bilirubin.
- Black pigment stones contain oxidised polymerised calcium bilirubinate, with calcium carbonate/phosphate, mucin, and small amounts of cholesterol.
- Brown pigment stones contain calcium bilirubinate plus calcium soaps, especially calcium palmitate and calcium stearate, cholesterol, and mucin.
- Mucin glycoproteins form the scaffold and cementing matrix in both cholesterol and pigment stones.
One-line viva distinction
- Cholesterol stone: pale-yellow, hard, radiating crystalline cut surface, cholesterol crystals with notched corners.
- Black pigment stone: black, small, multiple, friable, calcium bilirubinate.
- Brown pigment stone: brown, soft, greasy, laminated, infected bile ducts.
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