Jaundice
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Please help improve this article or section by expanding it. Further information might be found on the talk page or at requests for expansion. (May 2007) |
| Jaundice, NOS Classification and external resources |
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| Yellowing of the skin and sclera caused by Hepatitis A. | |
| ICD-10 | R17. |
| ICD-9 | 782.4 |
| DiseasesDB | 7038 |
| MedlinePlus | 003243 |
| MeSH | D007565 |
Jaundice, also known as icterus (attributive adjective: "icteric"), is yellowish discoloration of the skin, sclerae (whites of the eyes) and mucous membranes caused by hyperbilirubinemia (increased levels of bilirubin in the blood). This hyperbilirubinemia subsequently causes increased levels of bilirubin in the extracellular fluids. Typically, the concentration of bilirubin in the plasma must exceed 1.5 mg/dL[1], three times the usual value of approximately 0.5mg/dL[1], for the coloration to be easily visible. Jaundice comes from the French word jaune, meaning yellow.
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[edit] Normal Physiology
In order to understand how jaundice results, it is important to understand where the pathological processes that cause jaundice take their effect. It is also important to further recognize that jaundice itself is not a disease, but rather a symptom of an underlying pathological process that occurs at some point along the normal physiological pathway of the metabolism of bilirubin.
[edit] Pre-Hepatic events
When red blood cells have completed their life span of approximately 120 days, their membranes become fragile and prone to rupture. As the cell traverses through the reticuloendothelial system, their cell membranes rupture and the contents of the red blood cell is released into the blood. The component of the red blood cell that is involved in jaundice is hemoglobin. The hemoglobin released into the blood is phagocytosed by macrophages, and split into its heme and globin portions. The globin portion, being protein, is degraded into amino acids and plays no further role in jaundice. Two reactions then take place to the heme molecule. The first reaction is the oxidation of heme to form biliverdin.This reaction is catalyzed by microsomal enzyme heme oxygenase and it results in biliverdin (green color pigment), iron and carbon monoxide. Next step is reduction of biliverdin to yellow color tetrapyrol pigment bilirubin by cytosolic enzyme biliverdin reductase. This bilirubin is known as "unconjugated", "free" or "indirect" bilirubin. Approximately 4 mg per kg of bilirubin is produced each day.[2] The majority of this bilirubin comes from the breakdown of heme from expired red blood cells in the process just described. However approximately 20 per cent comes from other heme sources, including ineffective erythropoiesis, breakdown of other heme protrins such as muscle myoglobin and cytochrome enzymes.[2]
[edit] Hepatic events
The unconjugated bilirubin then travels to the liver through the bloodstream. Because this bilirubin is not soluble, however, it is transported through the blood bound to serum albumin. Once it arrives at the liver, it is conjugated with glucuronic acid (to form bilirubin diglucuronide, or just "conjugated bilirubin") to become more water soluble. The reaction is catalyzed by the enzyme UDP-glucuronide transferase.
[edit] Post Hepatic events
This conjugated bilirubin is excreted from the liver into the biliary and cystic ducts as part of bile. Intestinal bacteria convert the bilirubin into urobilinogen. From here the urobilinogen can take two pathways. It can either be further converted into stercobilinogen, which is then oxidized to stercobilin and passed out in the faeces, or it can be reabsorbed by the intestinal cells, transported in the blood to the kidneys, and passed out in the urine as the oxidised product urobilin. Stercobilin and urobilin are the products responsible for the coloration of faeces and urine, respectively.
[edit] Causes
When a pathological process interferes with the normal functioning of the metabolism and excretion of bilirubin just described, jaundice may be the result. Jaundice is classified into three categories, depending on which part of the physiological mechanism the pathology affects. The three categories are:
- Pre-hepatic: The pathology is occurring prior the liver
- Hepatic: The pathology is located within the liver
- Post-Hepatic: The pathology is located after the conjugation of bilirubin in the liver
[edit] Pre-hepatic
Pre-hepatic jaundice is caused by anything which causes an increased rate of hemolysis (breakdown of red blood cells). In tropical countries, malaria can cause jaundice in this manner. Certain genetic diseases, such as sickle cell anemia, spherocytosis and glucose 6-phosphate dehydrogenase deficiency can lead to increased red cell lysis and therefore hemolytic jaundice. Commonly, diseases of the kidney, such as hemolytic uremic syndrome, can also lead to coloration. Defects in bilirubin metabolism also present as jaundice. Jaundice usually comes with high fevers.
Laboratory findings include:
- Urine: no bilirubin present, urobilirubin > 2 units (except in infants where gut flora has not developed).
- Serum: increased unconjugated bilirubin.
[edit] Hepatic
Hepatic jaundice causes include acute hepatitis, hepatotoxicity and alcoholic liver disease, whereby cell necrosis reduces the liver's ability to metabolise and excrete bilirubin leading to a buildup in the blood. Less common causes include primary biliary cirrhosis, Gilbert's syndrome (a genetic disorder of bilirubin metabolism which can result in mild jaundice, which is found in about 5% of the population), Crigler-Najjar syndrome and metastatic carcinoma. Jaundice seen in the newborn, known as neonatal jaundice, is common, occurring in almost every newborn as hepatic machinery for the conjugation and excretion of bilirubin does not fully mature until approximately two weeks of age.
Laboratory Findings include:
- Urine: Conjugated bilirubin present, Urobilirubin > 2 units but variable (Except in children)
[edit] Post-hepatic
Post-hepatic jaundice, also called obstructive jaundice, is caused by an interruption to the drainage of bile in the biliary system. The most common causes are gallstones in the common bile duct, and pancreatic cancer in the head of the pancreas. Also, a group of parasites known as "liver flukes" live in the common bile duct, causing obstructive jaundice. Other causes include strictures of the common bile duct, biliary atresia, ductal carcinoma, pancreatitis and pancreatic pseudocysts. A rare cause of obstructive jaundice is Mirizzi's syndrome.
The presence of pale stools and dark urine suggests an obstructive or post-hepatic cause as normal feces get their color from bile pigments.
Patients also can present with elevated serum cholesterol, and often complain of severe itching or "pruritus".
[edit] Laboratory Results
[edit] Laboratory Tests
| Pre-hepatic Jaundice | Hepatic Jaundice | Post-hepatic Jaundice | |
|---|---|---|---|
| Total bilirubin | Normal / Increased | Increased | Increased |
| Conjugated bilirubin | Normal | Normal / Decreased | Increased |
| Unconjugated bilirubin | Increased | Normal / Increased | Normal |
| Urobilinogen | Increased | Normal / Increased | Decreased / Negative |
| Urine Colour | Normal | Dark | Dark |
| Stool colour | Normal | Normal | Pale |
[edit] Neonatal jaundice
Neonatal jaundice is usually harmless: this condition is often seen in infants around the second day after birth, lasting until day 8 in normal births, or to around day 14 in premature births. Serum bilirubin normally drops to a low level without any intervention required: the jaundice is presumably a consequence of metabolic and physiological adjustments after birth. In extreme cases, a brain-damaging condition known as kernicterus can occur; there are concerns that this condition has been rising in recent years due to inadequate detection and treatment of neonatal hyperbilirubinemia. Neonatal jaundice is a risk factor for hearing loss.[3]
[edit] Jaundiced eye
It was once believed persons suffering from the medical condition jaundice saw everything as yellow. By extension, the jaundiced eye came to mean a prejudiced view, usually rather negative or critical. Alexander Pope, in 'An Essay on Criticism' (1711), wrote: "All seems infected that the infected spy, As all looks yellow to the jaundiced eye."[4] Similarly in the mid 19th century the English poet Lord Alfred Tennyson wrote in the poem 'Locksley Hall': "So I triumphe'd ere my passion sweeping thro' me left me dry, left me with the palsied heart, and left me with a jaundiced eye."
[edit] Hyperbilirubinemia
What is hyperbilirubinemia? Hyperbilirubinemia is a condition in which there is too much bilirubin in the blood. When red blood cells break down, a substance called bilirubin is formed. Babies are not easily able to get rid of the bilirubin and it can build up in the blood and other tissues and fluids of the baby's body. This is called hyperbilirubinemia. Because bilirubin has a pigment or coloring, it causes a yellowing of the baby's skin and tissues. This is called jaundice.
Depending on the cause of the hyperbilirubinemia, jaundice may appear at birth or at any time afterward.
What causes hyperbilirubinemia? During pregnancy, the placenta excretes bilirubin. When the baby is born, the baby's liver must take over this function. There are several causes of hyperbilirubinemia and jaundice, including the following:
Physiologic jaundice Physiologic jaundice occurs as a "normal" response to the baby's limited ability to excrete bilirubin in the first days of life.
Breast milk jaundice About 2 percent of breastfed babies develop jaundice after the first week. Some develop breast milk jaundice in the first week due to low calorie intake or dehydration.
Jaundice from hemolysis Jaundice may occur with the breakdown of red blood cells due to hemolytic disease of the newborn (Rh disease), having too many red blood cells, or bleeding.
Jaundice related to inadequate liver function Jaundice may be related to inadequate liver function due to infection or other factors. Who is affected by hyperbilirubinemia? About 60 percent of term newborns and 80 percent of premature babies develop jaundice. Infants of diabetic mothers and of mothers with Rh disease are more likely to develop hyperbilirubinemia and jaundice.
Why is hyperbilirubinemia a concern? Although low levels of bilirubin are not usually a concern, large amounts can circulate to tissues in the brain and may cause seizures and brain damage. This is a condition called kernicterus.
What are the symptoms of hyperbilirubinemia? The following are the most common symptoms of hyperbilirubinemia. However, each baby may experience symptoms differently. Symptoms may include:
yellow coloring of the baby's skin (usually beginning on the face and moving down the body)
poor feeding or lethargy The symptoms of hyperbilirubinemia may resemble other conditions or medical problems. Always consult your baby's physician for a diagnosis.
How is hyperbilirubinemia diagnosed? The timing of the appearance of jaundice helps with the diagnosis. Jaundice appearing in the first 24 hours is quite serious and usually requires immediate treatment. When jaundice appears on the second or third day, it is usually "physiologic." However, it can be a more serious type of jaundice. When jaundice appears on the third day to the first week, it may be due to an infection. Later appearance of jaundice, in the second week, is often related to breast milk feedings, but may have other causes.
Diagnostic procedures for hyperbilirubinemia may include:
direct and indirect bilirubin levels These reflect whether the bilirubin is bound with other substances by the liver so that it can be excreted (direct), or is circulating in the blood circulation (indirect).
red blood cell counts
blood type and testing for Rh incompatibility (Coomb's test) Treatment for hyperbilirubinemia: Specific treatment for hyperbilirubinemia will be determined by your baby's physician based on:
your baby's gestational age, overall health, and medical history extent of the disease your baby's tolerance for specific medications, procedures, or therapies expectations for the course of the disease your opinion or preference Treatment depends on many factors, including the cause of the hyperbilirubinemia and the level of bilirubin. The goal is to keep the level of bilirubin from increasing to dangerous levels. Treatment may include:
phototherapy Since bilirubin absorbs light, jaundice and increased bilirubin levels usually decrease when the baby is exposed to special blue spectrum lights. Phototherapy may take several hours to begin working and it is used throughout the day and night. The baby's position is changed to allow all of the skin to be exposed to the light. The baby's eyes must be protected and the temperature monitored during phototherapy. Blood levels of bilirubin are checked to monitor if the phototherapy is working.
fiberoptic blanket Another form of phototherapy is a fiberoptic blanket placed under the baby. This may be used alone or in combination with regular phototherapy.
exchange transfusion to replace the baby's damaged blood with fresh blood Exchange transfusion helps increase the red blood cell count and lower the levels of bilirubin. An exchange transfusion is done by alternating giving and withdrawing blood in small amounts through a vein or artery. Exchange transfusions may need to be repeated if the bilirubin levels remain high.
ceasing breastfeeding for one or two days Treatment of breast milk jaundice often requires stopping the breastfeeding for one to two days and giving the baby formula often helps lower the bilirubin levels. Breastfeeding can then be resumed.
treating any underlying cause of hyperbilirubinemia, such as infection Prevention of hyperbilirubinemia: While hyperbilirubinemia cannot be totally prevented, early recognition and treatment are important in preventing bilirubin levels from rising to dangerous levels.
Online source http://www.healthsystem.virginia.edu/uvahealth/peds_hrnewborn/hyperb.cfm List of sources: http://www.healthsystem.virginia.edu/uvahealth/peds_hrnewborn/online.cfm
[edit] External links
[edit] See also
[edit] Footnotes
- ^ a b Guyton, Arthur; Hall, John (September 2005). Textbook of Medical Physiology. Saunders. ISBN 978-0721602400.
- ^ a b Pashankar, D; Schreiber, RA (July 2001). "Jaundice in older children and adolescents". Pediatrics in Review 22 (7): 219-226.
- ^ O'Keefe, Lori (2001-05-05). "Increased vigilance needed to prevent kernicterus in newborns". American Academy of Pediatrics 18 (5): 231.
- ^ From "The Dictionary of Cliches" by James Rogers (Ballantine Books, New York, 1985).
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