Общий билирубин (TBIL)

The Total Bilirubin (TBIL) test quantifies the sum of unconjugated (indirect) and conjugated (direct) bilirubin in serum. By reflecting heme catabolism and hepatobiliary handling of bilirubin, it serves as a core marker across prehepatic, hepatic, and posthepatic disorders. This assay is used to assess hemolytic processes (eg, sickle cell disease, hereditary spherocytosis, sideroblastic anemia, pernicious anemia), evaluate hepatocellular injury, and detect cholestasis or impaired bile flow. It supports the identification and severity assessment of viral hepatitis, helps confirm biliary tract patency, and aids in diagnosing neonatal jaundice of physiologic or hemolytic origin. The test may also assist in gauging severity following exposure to chemicals that provoke erythrocyte hemolysis and in evaluating disorders of the pancreas or adjacent structures that affect the biliary tree.

This test provides a quantitative measurement of total bilirubin— the sum of indirect (unconjugated) and direct (conjugated) fractions— in serum. Bilirubin is a yellow-brown end product of hemoglobin degradation that imparts characteristic color to bile, stool, and urine. Red blood cells circulate for approximately 90–150 days; about 1% of circulating erythrocytes are removed daily by the reticuloendothelial system (notably in the spleen, lymph nodes, and bone marrow), generating 100–250 mg of bilirubin per day. Indirect bilirubin released to plasma is subsequently taken up by hepatocytes and conjugated with glucuronic acid, producing the water-soluble direct fraction that enters bile, passes to the intestine, and is eliminated in feces. Under physiologic conditions, only a small amount of indirect bilirubin is present in blood as it transits from sites of production to the liver. Hyperbilirubinemia arises when this pathway is perturbed. Increased erythrocyte destruction augments heme turnover, producing excess indirect bilirubin and raising the serum total bilirubin concentration. Hepatocellular injury—commonly from viral hepatitis or from acute and chronic exposures to alcohol, medications, or household and industrial chemicals—disrupts membrane integrity, allowing intracellular constituents, including bilirubin, to enter the circulation. Impaired bile flow also elevates serum bilirubin: extrinsic compression from tumors, enlarged lymph nodes, or scarring, as well as dyskinesia of the biliary tract, can increase intraluminal pressure, distend canaliculi, and promote leakage of biliary components into blood. Less common causes of elevated bilirubin exist but are encountered infrequently and generally have limited clinical impact. Accordingly, total bilirubin testing supports the evaluation of disorders related to erythrocyte turnover, liver parenchymal function, and the patency of the biliary system, and it helps correlate biochemical abnormalities with the clinical picture of jaundice.