Grant Lafaine M., John Savio
University of Texas Southwestern Medical Center
SUNY Upstate Medical University
Cholestatic jaundice occurs due to cholestasis, a condition where bile flow significantly reduces or completely stops, leading to bile components (eg, bilirubin) accumulating in the bloodstream. Cholestasis can result from functional impairment of the hepatocytes in the secretion of bile or due to an obstruction at any level of the excretory pathway of bile, from the level of the hepatic parenchymal cells at the basolateral (sinusoidal) membrane of the hepatocyte to the ampulla of Vater in the duodenum. Cholestatic jaundice can be classified into intrahepatic or extrahepatic cholestasis, depending upon the level of obstruction to bile flow. Intrahepatic or functional cholestasis can be due to a condition involving the liver parenchymal cells or the intrahepatic bile ducts. Extrahepatic or obstructive cholestasis is due to an excretory block outside the liver and the extrahepatic bile ducts. Furthermore, intrahepatic cholestasis can be further subclassified as intralobular, affecting liver parenchymal cells and transporter molecules, or extralobular, affecting intrahepatic bile ducts. Clinically, cholestasis leads to the retention of bile constituents in the blood. The 2 primary constituents of bile are bilirubin and bile acids. Histologically, the retention of bilirubin in the hepatocytes, bile canaliculi, or bile ducts causes bilirubinostasis, which clinically manifests as jaundice. Biochemically, cholestasis is marked by the elevation of predominantly serum alkaline phosphatase. On the other hand, the stagnation of bile acids causes typical changes in the periportal region of the liver, termed cholate stasis, and presents clinically as pruritus. As the excretion of bilirubin follows hepatocellular pathways different from those of bile acids, serum bilirubin level may be normal in some instances of severe cholestasis (eg, anicteric cholestasis), and the patient may present with pruritus without jaundice. Prominent features of cholestasis are pruritus and malabsorption of fat and fat-soluble vitamins.
胆汁淤积性黄疸是由于胆汁淤积所致，胆汁淤积是指胆汁流动显著减少或完全停止，导致胆汁成分（如胆红素）在血液中蓄积。胆汁淤积可由肝细胞分泌胆汁的功能受损引起，也可由于胆汁排泄途径任何部位的梗阻所致，从肝细胞基底外侧（窦状隙）膜的肝实质细胞水平到十二指肠的 Vater 壶腹。根据胆汁流动梗阻的部位，胆汁淤积性黄疸可分为肝内胆汁淤积或肝外胆汁淤积。肝内或功能性胆汁淤积可能是由于涉及肝实质细胞或肝内胆管的疾病所致。肝外或梗阻性胆汁淤积是由于肝脏和肝外胆管以外的排泄受阻所致。此外，肝内胆汁淤积可进一步细分为小叶内胆汁淤积，影响肝实质细胞和转运分子，或小叶外胆汁淤积，影响肝内胆管。临床上，胆汁淤积导致胆汁成分在血液中潴留。胆汁的两种主要成分是胆红素和胆汁酸。组织学上，胆红素在肝细胞、胆小管或胆管中的潴留导致胆红素淤积，临床上表现为黄疸。生化方面，胆汁淤积的主要特征是血清碱性磷酸酶升高。另一方面，胆汁酸的潴留导致肝脏门周区域出现典型变化，称为胆盐淤积，临床上表现为瘙痒。由于胆红素的排泄途径与胆汁酸不同，在某些严重胆汁淤积的情况下（如无黄疸性胆汁淤积），血清胆红素水平可能正常，患者可能出现无黄疸的瘙痒症状。胆汁淤积的突出特征是瘙痒以及脂肪和脂溶性维生素吸收不良。
