Bilirubin is the principal breakdown product of red blood cells. The liver processes bilirubin into bile, which is transported by the biliary network of tubes within the liver to the gallbladder. The gallbladder releases bile into the small intestine, where it aids in digestion. A variety of disorders can cause an elevated bilirubin due to increased red blood cell breakdown, problems with bilirubin processing, or blockage of bile transport.
Hemolytic Anemia
Hemolytic anemia describes a group of conditions in which red blood cells undergo premature degradation. The National Heart, Lung and Blood Institute notes that red blood cells normally survive in blood circulation for approximately 120 days before removal and breakdown by the liver and spleen. With hemolytic anemia, red blood cell survival is significantly shortened. The increased rate of red blood cells destruction causes an elevation in circulating bilirubin, as the liver cannot keep up with the increased workload.
Hemolytic anemia may occur with a variety of disorders including sickle cell anemia, hereditary spherocytosis, thalassemia, glucose-6-phosphate dehydrogenase deficiency, autoimmune hemolytic anemia, drug-induced hemolytic anemia, hemolytic transfusion reaction and preeclampsia.
Liver Disease
Any disorder that disrupts liver cell function or destroys a significant number of liver cells can cause an elevated bilirubin level. In the review article "Jaundice in the Adult Patient" published in "American Family Physician," Drs. Sean Roche and Rebecca Kobos note that acute hepatitis caused by viruses such as hepatitis A and hepatitis B, reactions to medicines or toxins, and circulatory shock, can cause transient elevations in bilirubin. Chronic liver diseases such as alcoholic hepatitis, chronic hepatitis C, autoimmune hepatitis, hemochromatosis and nonalcoholic steatohepatitis often cause a persistently elevated bilirubin level. Inherited disorders of bilirubin metabolism, including Gilbert syndrome, Rotor's syndrome and Dubin-Johnson syndrome, can also cause chronic elevations in circulating bilirubin.
Biliary Diseases
Diseases of the biliary tract system, which transports bile to the gallbladder, can cause obstruction of bile flow with a resultant buildup of circulating bilirubin. Obstruction of bile flow is termed cholestasis. Dr. David Dugdale III of the University of Washington School of Medicine notes in a National Library of Medicine Medline Plus entry that possible causes of cholestasis within the liver include primary biliary cirrhosis, primary sclerosing cholangitis, sarcoidosis, Sjögren's syndrome and pregnancy. Bile flow obstruction can also occur outside the liver. Dr. Dugdale reports that possible causes include gallstones blocking the release of bile into the intestine, gallbladder or bile duct cancer, cysts, cholangitis, pancreatitis, pancreatic tumors and narrowing of the bile transport ducts, or bile duct strictures.
References
- National Heart, Lung and Blood Institute: Hemolytic Anemia
- "American Family Physician"; Jaundice in the Adult Patient; Sean P. Roche, M.D., Rebecca Kobos, M.D.; January 2004
- Merck Manual for Healthcare Professionals: Chronic Hepatitis
- Medline Plus: Cholestasis
- "Harrison's Principles of Internal Medicine, 16th Edition"; Dennis L. Kasper, M.D., et al., Editors; 2004
