Bile Acids

Bile acids are indispensable molecules that are needed for the absorption of fat and fat soluble vitamins. They are synthesized in the liver, excreted in the intestine where they perform their absorptive function, are reabsorbed and transported back to the liver thereby completing the enterohepatic cycle. Synthesis of bile acids is needed to compensate for fecal loss, and several hereditary disorders have been identified in bile acid synthesis, that is the conversion of cholesterol into the two primary bile acids chenodeoxycholic and cholic acid. Patients can have cholestasis, jaundice, liver disease, fat malabsorption, fat-soluble vitamin deficiency, but also neurological disease. As most bile acid synthesis defects have a characteristic bile acid profile, bile acid analysis by tandem mass spectrometry in plasma and urine should be performed in patients with these symptoms. In this chapter, we focus on the analysis of bile acids using mass spectrometry (MS), both ultra performance liquid chromatography (UPLC)-MS/MS and flow-injection MS/MS to perform quantitative and qualitative analysis, respectively.