Black and brown pigment gallstones differ in microstructure and microcomposition.

Area of Science:

• Gastroenterology
• Biochemistry
• Materials Science

Background:

• Pigment gallstones are broadly classified into black and brown subtypes.
• These subtypes exhibit variations in chemical makeup and the processes leading to their formation.

Purpose of the Study:

• To investigate the microstructural and microchemical differences between black and brown pigment gallstones.
• To determine if these differences correlate with distinct formation mechanisms.

Main Methods:

• Scanning electron microscopy (SEM) was employed to analyze stone surfaces and cross-sections.
• Microchemical techniques, including electron probe microanalysis and plasma/argon ion etching, were used to identify elemental and chemical composition.
• Specific attention was paid to the distribution of calcium bilirubinate, calcium palmitate, and protein structures.

Main Results:

• Black bilirubinate and black phosphate stones displayed smooth, homogenous surfaces, while brown stones were rough with lamellated bands.
• Black stones showed high sulfur and copper concentrations, with sulfur in a low valence state, suggesting protein disulfide linkages.
• Brown stones contained significant calcium palmitate in lighter bands and calcium bilirubinate in darker bands.
• Protein networks were observed in black stones but not brown stones; calcium bilirubinate had a rod-shaped arrangement in black stones.

Conclusions:

• Structural and compositional disparities between black noncarbonate and brown pigment gallstones support divergent formation mechanisms.
• The layered structures in black carbonate and brown stones indicate that biliary composition fluctuations influence gallstone growth.