Jaundice is a condition in which a person's skin and the whites of the eyes are discolored yellow due to an increased level of bile pigments in the bloodresulting from liver disease. Jaundice is sometimes called icterus, from a Greek word for the condition.
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 theintestines 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 forall nutrients, toxins, and drugs absorbed by the digestive tract. The liveralso 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, itaccumulates and discolors other tissues. The normal total level of bilirubinin blood serum is between 0.2 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 bileducts, 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 signalfrom 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 ofVater. After entering the intestine, the bile and pancreatic secretions together help in the process of digestion.
There are many different causes for jaundice, but they can be divided into three categories based on where they start--before, in, or after the liver (pre-hepatic, hepatic, and post-hepatic). When bilirubin begins its life cycle, it cannot be dissolved in water. The liver changes it so that it is soluble inwater. These two types of bilirubin are called unconjugated (insoluble) andconjugated (soluble). Blood tests can easily distinguish between these two types of bilirubin.
Bilirubin begins as hemoglobin in the blood-forming organs, primarily the bone marrow. If the production of red blood cells (RBCs) falls below normal, theextra hemoglobin finds its way into the bilirubin cycle and adds to the pool.
Once hemoglobin is in the red cells of the blood, it circulates for the lifespan of those cells. The hemoglobin that is released when the cells die is turned into bilirubin. If for any reason the RBCs die at a faster rate than usual, bilirubin can accumulate in the blood and cause jaundice.
Many disorders speed up the death of red blood cells. The process of red blood cell destruction is called hemolysis, and the diseases that cause it are called hemolytic disorders. If red blood cells are destroyed faster than they can be produced, the patient develops anemia. Hemolysis can occur in anumber of diseases, disorders, conditions, and medical procedures, includingmalaria; as a side effects of certain drugs, including some antibiotic and anti-tuberculosis medicines, drugs that regulate the heartbeat, and levodopa, adrug used to treat Parkinson's disease); certain drugs in combination with ahereditary enzyme deficiency known as glucose-6-phosphate dehydrogenase (G6PD); poisons (snake and spider venom, certain bacterial toxins, copper, and some organic industrial chemicals directly attack the membranes of red blood cells); artificial heart valves; hereditary RBC disorders; enlargement of the spleen; diseases of the small blood vessels; immune reactions to RBCs; transfusions; kidney failure and other serious diseases; erythroblastosis fetalis, a disease of newborns marked by the presence of too many immature red blood cells in the baby's blood; and high bilirubin levels in newborns.
Normal newborn jaundice is the result of two conditions occurring at the sametime--a pre-hepatic and a hepatic source of excess bilirubin. First of all,the baby at birth immediately begins converting hemoglobin from a fetal typeto an adult type. The fetal type of hemoglobin was able to extract oxygen from the lower levels of oxygen in the mother's blood. At birth the infant can extract oxygen directly from his or her own lungs and does not need the fetalhemoglobin any more. So fetal hemoglobin is removed from the system and replaced with adult hemoglobin. The resulting bilirubin loads the system and places demands on the liver to clear it. But the liver is not quite ready for thetask, so there is a period of a week or so when the liver has to catch up. During that time the baby is jaundiced.
Liver diseases of all kinds threaten the organ's ability to keep up with bilirubin processing. Starvation, circulating infections, certain medications, hepatitis, and cirrhosis can all cause hepatic jaundice, as can certainhereditary defects of liver chemistry, including Gilbert's syndrome and Crigler-Najjar syndrome.
Post-hepatic forms of jaundice include the jaundices caused by failure of soluble bilirubin to reach the intestines after it has left the liver. These disorders are called obstructive jaundices. The most common cause of obstructivejaundice is the presence of gallstones in the ducts of the biliary system. Other causes have to do with birth defects and infections that damage the bileducts; drugs; infections; cancers; and physical injury. Some drugs--and pregnancy on rare occasions--simply cause the bile in the ducts to stop flowing.
Certain chemicals in bile may cause itching when too much of them ends up inthe skin. In newborns, insoluble bilirubin may get into the brain and do permanent damage. Long-standing jaundice may upset the balance of chemicals in the bile and cause stones to form. Apart from these potential complications andthe discoloration of skin and eyes, jaundice by itself is inoffensive. Othersymptoms are determined by the disease producing the jaundice.
In many cases the diagnosis of jaundice is suggested by the appearance of thepatient's eyes and complexion. The doctor will ask the patient to lie flat on the examining table in order to feel (palpate) the liver and spleen for enlargement and to evaluate any abdominal pain. The location and severity of abdominal pain and the presence or absence of fever help the doctor to distinguish between hepatic and obstructive jaundice.
Disorders of blood formation can be diagnosed by more thorough examination ofthe blood or the bone marrow, where blood is made. Occasionally a bone marrow biopsy is required, but usually the blood itself will reveal the diagnosis.The spleen can be evaluated by an ultrasound examination or a nuclear scan if the physical examination has not yielded enough information.
Liver disease is usually assessed from blood studies alone, but again a biopsy may be necessary to clarify less obvious conditions. A liver biopsy is performed at the bedside. The doctor uses a thin needle to take a tiny core of tissue from the liver. The tissue sample is sent to the laboratory for examination under a microscope.
Newborns are more likely to have problems with jaundice if:
- They are premature.
- They are Asian or Native Americans.
- They have been bruised during the birth process.
- They have lost too much weight during the first few days.
- They are born at high altitude.
- The mother has diabetes.
- Labor had to be induced.
Disease in the biliary system can be identified by imaging techniques, of which there are many. 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 intothe bile ducts. It can be done through a thin needle pushed straight into theliver or through a scope passed through the stomach that can inject dye intothe Ampulla of Vater. CT and MRI 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 itselfrequires 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 tosuspect increased hemolysis in the newborn, the bilirubin level must be measured repeatedly during the first few days of life. If the level of bilirubinshortly 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 amountof bilirubin until a few decades ago. Then it was discovered that bright bluelight will render the bilirubin harmless. 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 hemolysisor arrest the flow of bile must be stopped immediately.
Most liver diseases have no specific cure, but the liver is so robust that itcan heal from severe damage and regenerate itself from a small remnant of its original tissue.