Bilirubin, Direct

Measurement of the levels of bilirubin is used in the diagnosis and treatment of liver, hemolytic, hematologic, and metabolic disorders, including hepatitis and gallbladder obstruction. The assessment of direct bilirubin is helpful in the differentiation of hepatic disorders.

Bilirubin is final product in heme catabolism. Heme is part of haemoglobin, protein in erythrocytes that binds and transports oxygen through our body. There are 2 types of bilirubin, direct and indirect. The first to appear is unconjugated bilirubin (also called indirect, or pre-hepatic). It makes a complex with albumines and goes straight to liver for conjugation in order to become soluble in water and eliminated from body. The main enzyme in this process (UDP-glucuronyl transferase) is localized in liver cells. Through many chemical reactions, the final product of this process is conjugated bilirubin (also called direct or hepatic), that now goes to small intestine (duodenum) through bile ducts. The measurement of direct bilirubin in blood represents liver function, since liver is a place where it originally comes from, but it also represents function of gallbladder and bile ducts. Elevated levels of direct bilirubin could be sign of hepatobiliary disease, such as hepatitis, cirrhosis or gallstones, obstruction of bile ducts (stones, tumor of pancreatic head). Elevated level of direct bilirubin is accompanied by jaundice (yellowish coloration of skin and sclerae), light-coloured feces, and dark-coloured urine. The reference range for direct bilirubin is 0.1-0.4 mg/dL.

This test is performed in following conditions such as:

• Renal function impairment

Also Known As: Bilirubin Conjugated