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.