Mechanism of stone formation
Calculus formation is based on three key processes:
- Dyscholia — disturbance of the chemical composition of bile.
- Stasis — bile stasis in the gallbladder cavity.
- Infectious factor — inflammatory processes in the biliary tract.
The process of stone formation begins with the creation of an organic matrix, onto which salt crystals subsequently layer.
Classification and Morphology
Stones are classified according to their chemical composition:
- Cholesterol stones: the most frequent (80%). They can be pure cholesterol (single, rounded) or mixed (multiple, layered on cross-section).
- Pigment stones: dark brown or black, often having an irregular polygonal shape with facets.
- Calcium stones: less common, characterized by high density.
In mixed stones, the gallbladder is often enlarged, its wall is thickened, and the mucous membrane acquires a granular appearance.
Clinical manifestations
Despite frequent asymptomatic carriage, as the disease progresses, patients note:
- Sensation of heaviness in the right upper quadrant.
- Spastic pain (biliary colic).
- Dyspeptic disorders: nausea and bitter taste in the mouth.
- Obstructive jaundice occurring when a stone blocks the bile duct.
Briefly: answers to topical questions
What complications can develop in cholelithiasis?
Local, inflammatory, and obstructive complications can develop in cholelithiasis:
- Local lesions — pressure sores of the gallbladder wall leading to perforation, adhesion formation, and fistulas.
- Inflammatory processes — cholecystitis, cholangitis, and cholangiolitis.
- Obstructive conditions — biliary tract obstruction and biliary colic.
- Damage to adjacent organs — acute pancreatitis.
Which components form the organic matrix of a gallstone?
The organic matrix of a gallstone is formed from cellular, protein, and microbial components. It includes:
- Cellular elements — desquamated epithelial cells, leukocytes, and cellular detritus.
- Protein substances — mucus, fibrin, collagen, and other secretion proteins.
- Microorganisms — bacteria acting as an organic basis during inflammatory processes.
The formation of the colloidal matrix is primary according to the colloidal theory of stone formation, or occurs secondarily during salt crystallization.
As a result of what pathological processes do pigment stones form?
Pigment stones form as a result of pathologies accompanied by an excess of bilirubin or infectious-inflammatory changes in the biliary tract. Two pathogenetic variants are distinguished:
- Black stones — form against the background of increased hemolysis (e.g., in congenital hemolytic anemias, sickle cell disease) and in liver cirrhosis due to increased bilirubin concentration.
- Brown stones — form against the background of chronic inflammation in the intra- and extrahepatic bile ducts.
What microscopic changes are observed in the gallbladder wall during the long-term course of cholelithiasis?
During the long-term course of cholelithiasis, microscopic signs of chronic calculous cholecystitis develop in the gallbladder wall. The following changes are observed:
- Mucous membrane — atrophy, sclerosis of the lamina propria, formation of Rokitansky-Aschoff sinuses.
- Muscular layer — hypertrophy or sclerosis.
- Inflammatory infiltration — lymphomacrophagic infiltration (leukocytes appear during exacerbation).
In special forms, extensive fibrosis extending beyond the wall (xanthogranulomatous variant) or replacement of structures with dense hyaline sclerosis with possible calcification (hyalinizing variant) is detected.
What is the biochemical mechanism of dyscholia development in the formation of cholesterol stones?
The biochemical mechanism of dyscholia consists in the disturbance of the ratio of bile micelle lipids (dyslipoproteinemia). The process is caused by the following factors:
- Enzymatic shifts — increase in HMG-CoA reductase activity (enhances cholesterol synthesis) or decrease in 7α-hydroxylase activity (inhibited by estrogens or allosterically inhibited by bile acids).
- Change in bile composition — absolute increase in cholesterol concentration and decrease in the level of solubilizers (bile acids and phospholipids/lecithin).
As a result, the lithogenic index (the ratio of cholesterol to the sum of bile acids and phospholipids) exceeds the 1:10 proportion, leading to cholesterol precipitation and crystallization.
The "4F" rule (in the context of risk factors): Female, Forty (age 40+), Fat (obesity), Fertile (multiparity).
Class and exam questions
Where is pain localized in biliary colic?
Typical localization of pain — right upper quadrant.
How do cholesterol stones differ on cross-section?
Mixed cholesterol stones have a layered structure: alternation of dark layers (pigments) and light layers (cholesterol).
What factors contribute to the development of cholelithiasis?
In addition to age and sex, significant factors are obesity, diabetes mellitus, use of oral contraceptives, and ileal resection.
What else to study on this topic
- Pathophysiology of biliary colic in duct obstruction.
- Differential diagnosis of pigment and cholesterol stones.
- The role of the organic matrix in initiating crystallization.
- Morphological changes of the gallbladder wall in chronic cholecystitis.
- Complications of cholelithiasis (cholangitis, gallbladder hydrops).
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