Jaundice 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.

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. Rat fever (leptospirosis) can also cause jaundice.

Laboratory findings include:

* Urine: no bilirubin present, urobilirubin > 2 units (except in infants where gut flora has not developed).
* Serum: increased unconjugated bilirubin.

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, metastatic carcinoma and Niemann-Pick disease, type C. 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).

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" can 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".

No one test can differentiate between various classifications of jaundice. A combinations of liver function tests is essential to arrive at a diagnosis.
Pre-hepatic Jaundice Hepatic Jaundice Post-hepatic Jaundice
Total bilirubin Normal / Increased Increased Increased
Conjugated bilirubin Increased Normal Increased
Unconjugated bilirubin Increased Normal / Increased Normal
Urobilinogen Increased Normal / Increased Decreased / Negative
Urine Color Normal Dark Dark
Stool Color Normal Normal Pale
Alkaline phosphatase levels Normal Increased Increased
Alanine transferase and Aspartate transferase levels Normal Increased Increased
Conjugated Bilirubin in Urine Not Present Present Present
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