Jaundice Health Article

Definition

Jaundice is a condition in which the patient has a yellow hue because of high blood levels of bilirubin, a breakdown product of hemoglobin that is potentially toxic. The yellow discoloration is most noticeable in the skin, the sclera (whites of the eyes), and the inner surface of the eyelids.

Description

Jaundice is a physical sign or finding, not a disease. Many different diseases or conditions may cause a person's bilirubin level to be elevated. Most important to the understanding of causes of this sign is a good explanation of normal liver function with regard to the production and excretion of bile. Bile is a fluid excreted by the liver that aids in digestion and absorption of fats.

The liver is a large, solid organ in the right upper quadrant of the abdomen. It is the premier "chemical processing plant" in the body; most incoming and outgoing chemicals pass through it. It is the first stop for all nutrients, toxins, and drugs absorbed by the digestive tract. The liver also collects waste products from the blood for disposal. Many of these outward-bound chemicals (including bilirubin) are excreted into the bile.

Bile is made up of water; chemicals that act as detergents; and substances such as glycogen, bilirubin, cholesterol, and other byproducts of hepatic metabolism. It is formed by cellular metabolism and passes into the network of hepatic bile ducts, which join to form the common duct. A branch of this tube carries bile to the gall-bladder, where it is stored and concentrated. When fats enter the stomach, the gallbladder secretes bile into the common bile duct. Before the common bile duct reaches the duodenum, it is joined by another duct from the pancreas. The bile and the pancreatic juice are triggered to enter the intestine through a valve called the ampulla of Vater by the presence of partially digested fats in the duodenum. After entering the intestine, the bile and pancreatic secretions together help to complete the process of digestion.

The liver removes toxins from the bloodstream, including bilirubin. Bilirubin is a potentially toxic waste product from the breakdown of hemoglobin, the oxygen-carrying molecule of red blood cells (RBCs). When bilirubin is first released from old RBCs or other sources, it cannot be dissolved in water. The liver changes it so that it is soluble in water. These two forms are called unconjugated (insoluble) and conjugated (soluble) bilirubin. Because of the type of laboratory test performed on the different forms of this molecule, unconjugated bilirubin is also called indirect bilirubin, and conjugated bilirubin is called direct bilirubin. Bilirubin is a bright yellow pigment and gives bile its characteristic color. If bilirubin cannot be cleared from the body in a timely fashion, it leaks into body tissues and stains them yellow temporarily, resulting in jaundice. The normal level of bilirubin in blood serum is between 0.2 mg/dL and 1.2 mg/dL. When it rises to 3 mg/dL or higher, jaundice becomes evident. "Icteric" is an adjective (based on the Greek word for jaundice) used to describe a jaundiced patient.

Causes and symptoms

There are many different causes of jaundice, but they can be divided into three categories: before, during, or after the liver has performed its task of making bilirubin soluble. These categories can also be called prehepatic, hepatic, and posthepatic causes of jaundice.

Prehepatic causes of jaundice

There are many different prehepatic causes of jaundice. When old RBCs die, hemoglobin is released into the bloodstream. When the rate of formation of new RBCs and the rate of loss of old RBCs are well balanced, the normal liver can keep pace with disposal of used hemoglobin. If the body is having difficulty making RBCs (due to mineral or vitamin deficiencies), hemoglobin may leak into circulation and overwhelm the liver. Conversely, if RBCs are destroyed rapidly, the liver may also be overwhelmed. Disorders that cause RBCs to dis-integrate prematurely are called hemolytic disorders.

One cause of hemolysis (or prematurely destroyed RBCs) to be aware of starts at the neonatal point, in babies born of Rh-negative mothers. Other causes include a long list of drugs, among them rifampin, methyldopa, certain antibiotics, quinine, and levodopa. Trauma can also destroy RBCs. Some common causes of trauma include surgery for mechanical heart valves, implants, and roughened surfaces of blood vessels such as occur in microangiopathic hemolytic anemia. The parasite that causes malaria develops inside red blood cells and ruptures the RBCs when it is mature. A number of hereditary defects affect red blood cells, including glucose-6-phosphate dehydrogenase (G6PD) deficiency (in which RBCs disintegrate under certain stresses, particularly when exposed to certain drugs), sickle-cell disease (in which the structure of hemoglobin is abnormal), and spherocytosis (in which a protein in the outer membrane of the RBC causes weakness in the membrane).

An enlarged spleen can also cause hemolysis. The spleen is the reservoir organ, located near the upper end of the stomach, that filters the blood. It is supposed to filter out and destroy only worn-out RBCs. If it becomes enlarged, it filters out normal cells as well. A wide variety of conditions, including many causes of hemolysis listed above, can enlarge the spleen to the point where it removes too many red blood cells. Also, in several types of cancer (such as chronic leukemia) and immune-system diseases, antibodies are produced that react with RBCs and destroy them. In addition, if a patient is given an incompatible blood type, it sets off an immune reaction, and hemolysis results.

In all causes of prehepatic jaundice, the predominant bilirubin is insoluble—that is, unconjugated. Hemolysis alone will rarely cause the total bilirubin level to rise above 7 mg/dL.