Jaundice
Jaundice
Jaundice is a condition in which a person’s skin and the whites of the eyes are discolored a shade of yellow due to an increased level of bile pigments in the blood resulting from liver disease. It is sometimes called icterus, from a Greek word for the condition. Jaundice is not a disease buta symptom of an underlying disease or condition. It is caused by too much bilirubin in the blood stream, and is characterized by yellowness of skin, sclera (white of eyes), mucous membranes, and of body fluids such urine and blood plasma. The resulting yellow color (jaune means yellow in French) is also described by the Latin term icterus.
Liver and bile
In order to understand jaundice, it is useful to know about the role of the liver in producing bile. The most important function of the liver is the processing of chemical waste products like cholesterol and excreting them into the intestines as bile. The liver is the premier chemical factory 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 chemicals from the blood for processing. Many of these outward-bound chemicals are excreted into the bile. One particular substance, bilirubin, is yellow. Bilirubin is a product of the breakdown of hemoglobin, which is the protein inside red blood cells. If bilirubin cannot leave the body, it accumulates and discolors other tissues. The normal total level of bilirubin in blood serum is between 0.2 milligrams per deciliter (mg/dL) and 1.2 mg/dL. When it rises to 3 mg/dL or higher, the person’s skin and the whites of the eyes become noticeably yellow.
Bile is formed in the liver. It then passes into the network of hepatic bile ducts, which join to form a single tube. A branch of this tube carries bile to the gallbladder, where it is stored, concentrated, and released on a signal from the stomach. Food entering the stomach is the signal that stimulates the gallbladder to release the bile. The tube, which is now called the common bile duct, continues to the intestines. Before the common bile duct reaches the intestines, it is joined by another duct from the pancreas. The bile and the pancreatic juice enter the intestine through a valve called the ampulla of Vater. After entering the intestine, the bile and pancreatic secretions together help in the process of digestion.
Bilirubin
Most bilirubin, which is a reddish pigment, is a byproduct of red blood cells. When a red blood cell, which has a lifespan of about 120 days, is no longer functional. It is recycled by organs such as the spleen and liver. Hemoglobin, the red pigment in a red blood cell, is broken down, or catabolized, into several substances that are either used to make new blood cells, proteins, or other pigments. After the bilirubin is liberated from the red blood cell, it is bound to albumin and transported via blood plasma to the liver, where it is conjugated or joined to glucuronic acid, and excreted into the bile ducts. Bilirubin is also the prominent pigment of bile, a digestive substance secreted by the liver into the gallbladder and small intestine (jejunum), and it is also responsible for the brown color of feces.
Jaundice
There are several ways in which a person can have too much bilirubin, or become jaundiced. Hemolytic jaundice occurs when the liver is overloaded with bilirubin. In conditions and diseases causing hemolysis (the separation of hemoglobin from the red blood cells), including hemolytic anemias, incompatible blood transfusion, and extreme heat or cold, the liver is unable to remove enough bilirubin from the blood stream. Liver cells which are damaged by hepatocellular disease (hepatitis, cirrhosis), toxins, tumors, or inflammatory conditions, are unable to conjugate bilirubin, thus preventing normal excretion. Neonatal jaundice, especially in premature infants, is fairly common. This type of jaundice is caused by the fact that the liver is immature and lacks specific enzymes to conjugate bilirubin, and a large amount of bilirubin is consequently excreted into the blood stream instead of being incorporated into bile.
Causes
There are many different causes for jaundice, but they can be divided into three main categories based on where they start—before, in, or after the liver (prehepatic, hepatic, and post-hepatic). When bilirubin
begins its life cycle, it cannot be dissolved in water. The liver changes bilirubin so that it becomes soluble in water. These two types of bilirubin are called uncon-jugated (insoluble) and conjugated (soluble). Blood tests can easily distinguish between these two types of bilirubin. The most common cause of jaundice is obstruction of bile flow through the biliary system. For example, a gallstone, a liver tumor, or a pancreatic tumor can block a biliary duct. The treatment of jaundice depends on the cause.
Identification
Disease in the biliary system can be identified by imaging techniques, of which there are many types. X rays are taken a day after swallowing a contrast agent that is secreted into the bile. This study gives functional as well as anatomical information. There are several ways of injecting x-ray dye directly into the bile ducts. It can be done through a thin needle pushed straight into the liver or through a scope passed through the stomach that can inject dye into the Ampulla of Vater. CT (computed tomography) and MRI (magnetic resonance imaging) scans are very useful for imaging certain conditions like cancers in and around the liver or gall stones in the common bile duct.
Newborns are the only major category of patients in whom the jaundice itself requires attention. Because the insoluble bilirubin can get into the brain, the amount in the blood must not go over certain levels. If there is reason to suspect increased hemolysis in the newborn, the bilirubin level must be measured repeatedly during the first few days of life. If the level of bilirubin shortly after birth threatens to go too high, treatment must begin immediately. Exchanging most of the baby’s blood was the only way to reduce the amount of bilirubin until the middle part of the twentieth century. At that time, it was discovered that bright blue light renders the bilirubin harmless. (Actually, in 1956, Sister Ward, a nurse at Rochford General Hospital in England, accidentally discovered the use of blue light for this purpose.) Now jaundiced babies are fitted with eye protection and placed under bright fluorescent lights. The light chemically alters the bilirubin in the blood as it passes through the baby’s skin.
Hemolytic diseases are treated, if at all, with medications and blood transfusions, except in the case of a large spleen. Surgical removal of the spleen (splenectomy) can sometimes cure hemolytic anemia. Drugs that cause hemolysis or arrest the flow of bile must be stopped immediately.
Most liver diseases have no specific cure, but the liver is so robust that it can heal from severe damage and regenerate itself from a small remnant of its original tissue.