What laboratory studies suggest the etiology of biliary obstruction? What is the pathophysiology basis for this?
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Biliary obstruction is the blockage of any duct that carries bile from the liver to the gallbladder and small intestine (Coucke, Akbar, Kahloon, & Lopez, 2020). Bile is made in the liver and contains a mix of bilirubin, cholesterol, fats, bile acids, and salts (Coucke et al., 2020). Bile is also an alkaline, bitter-tasting, yellowish-green fluid (McCance, & Huether, 2019). Bile has different functions, including excretory, emulsifying dietary fats, facilitating intestinal absorption, eliminating cholesterol, and protecting the organism from enteric infections by excreting immune globulin A (Boyer, 2013). Bile is produced by the liver and flow to the common hepatic duct. Approximated 50% of bile flows into the cystic duct and stored in the gallbladder (Coucke et al., 2020). The rest of the bile flows through the common bile duct and converging through the main pancreatic duct to empty into the duodenum (Coucke et al., 2020). When there is a biliary obstruction, it disrupts the bile flow and can lead to serious complications such as hepatic dysfunction, renal failure, bleeding problems, infection, and others (Coucke et al., 2020).
The most common cause of blocked bile ducts are gallstones (Harvard Health Publishing, 2020). Biliary obstruction is mainly divided into intrahepatic cholestasis and extrahepatic biliary obstruction (Coucke et al., 2020). The intrahepatic cholestasis can be from different diseases such as primary biliary cholangitis, acute hepatitis, and drug-induced liver injury (Coucke et al., 2020). In cholelithiasis, gallstones are formed by the impaired metabolism of cholesterol, bilirubin, and bile acids (McCance, & Huether, 2019). There are three types of gallstones and depend on chemical composition, including cholesterol, pigmented, and mixed (McCance & Huether, 2019). The obstruction causes the gallbladder to become extended, inflamed and decreased blood flow, and bilirubin would back up and enter the bloodstream. As a result, the biliary obstruction can lead to jaundice, ischemia, necrosis, bacterial infection, and perforation of the gallbladder (McCance, & Huether, 2019).
Several abnormal laboratory studies indicate biliary obstruction, which including the elevation of serum bilirubin level, alkaline phosphatase, levels of serum transaminases, and hepatitis serology (Bonheur & Kapoor, 2019). The obstruction of bile ducts can also increase urine urobilinogen level, clay-colored stools, and jaundice (McCance, & Huether, 2019). The normal level of total serum bilirubin values is in the range of 0.2-1.2 mg/dL. For patients with obstructive jaundice, their total serum bilirubin can elevate the level of 3mg/dL and can also have dark-colored urine (Coucke et al., 2020). The common signs and symptoms for cholangitis patients are right upper quadrant pain, nausea and vomiting, fever, and yellowing of the skin. They can also develop complications with mental status change and hemodynamic shock (Coucke et al., 2020). Therefore, clinicians can diagnose patients with biliary obstruction based on abnormal laboratory studies and presenting symptoms during office visits.
References
Bonheur, J. L., & Kapoor, V. K. (2019). Biliary obstruction workup. Medscape. Retrieved from: https://emedicine.medscape.com/article/187001-workup
Boyer J. L. (2013). Bile formation and secretion. Comprehensive Physiology, 3(3), 1035–1078. Retrieved from:
Coucke, E., Akbar, H., Kahloon, A., & Lopez, P. (2020). Biliary Obstruction. StatPearls. Retrieved from: https://www.ncbi.nlm.nih.gov/books/NBK539698/
Harvard Health Publishing. (2020). Bile duct diseases. Retrieved from: https://researchguides.gonzaga.edu/az.php?a=p
McCance, K.L., & Huether, S.E. (2019). Pathophysiology: The biologic basis for disease in adults and children (8th ed.). St. Louis, MI: Elsevier.