Fisiopatología de la litiasis biliar. Cálculos de colesterol

RESUMO

Biliary stones constitute an important issue in public health, until recently treated exclusively by surgical means. In the western world 80-90 percent of stones are composed of cholesterol, secondary to abnormalities in cholesterol and lipoprotein metabolism. In the last two decades significant advances in the treatment of this problem have been made, such as medical dissolution and extracorporeal lithotripsy. The most significant risk factors are obesity, rapid weight loss, female sex, pregnancy, diabetes, hypertriglyceridemia, estrosalts derived from cholesterol are hydrophylic sterols that are essential to micelle formation. The predominance of the hydrophylic domain makes them amphophylic. Primary bile salts cholate and deoxycholate are synthetized in the liver; secondary bile salts deoxycholate and lithocholate derived from primary ones by bacterial transformation in the gut; tertiary bile salts ursodeoxycholate and sulpholithocholate derived from secondary salts by bacterial action. Lecithin is the main phospholipid in bile, its main fuction is to solubilize cholesterol associated to bile salts. Micelles are complex structures made of cholesterol, lecithin and bile salts. Experimentally a triangular diagram has been designed representing molar concentrations of cholesterol, lecithin and bile salts. This diagram facilitates the understanding of biliary stones formation. Changing is components keeping constant total lipids, identifics several phases essential in stones formation, such as the micellar phase and the metastable phase. Supersaturated bile results from excess of cholesterol or deficiency of bile salts, and represents the initial abnormality that predispose to stones formation...