JAUNDICE

It happens when the serum bilirubin exceeds 2.5mg/dl (43fmol/L), the abnormal elevated concentration of bilirubin in the blood causes the skin, sclerae become yellow-tinged or greenish-yellow in color. It is also known as icterus (attributive adjective: icteric), is a yellowish discoloration of the skin, the conjunctival membranes over the sclerae (whites of the eyes), and other mucous membranes caused by hyperbilirubinemia (increased levels of bilirubin in the blood).

Jaundice itself is not a disease, but rather a sign of one of many possible underlying pathological processes that occur at some point along the normal physiological pathway of the metabolism of bilirubin.

When red blood cells have completed their life span of approximately 120 days, or when they are damaged, their membranes become fragile and prone to rupture. As each red blood cell traverses through the reticuloendothelial system, its cell membrane ruptures when its membrane is fragile enough to allow this. Cellular contents, including hemoglobin, are subsequently released into the blood. The hemoglobin is phagocytosed by macrophages, and split into its heme and globin portions. The globin portion, a protein, is degraded into amino acids and plays no role in jaundice. Two reactions then take place with the heme molecule. The first oxidation reaction is catalyzed by the microsomal enzyme heme oxygenase and results in biliverdin (green color pigment), iron and carbon monoxide. The next step is the reduction of biliverdin to a yellow color tetrapyrol pigment called bilirubin by cytosolic enzyme biliverdin reductase. This bilirubin is "unconjugated," "free" or "indirect" bilirubin. Approximately 4 mg per kg of bilirubin is produced each day. The majority of this bilirubin comes from the breakdown of heme from expired red blood cells in the process just described. However approximately 20 percent comes from other heme sources, including ineffective erythropoiesis, and the breakdown of other heme-containing proteins, such as muscle myoglobin and cytochromes.

Hemolytic jaundice – increased destruction of red blood cells. The plasma with bilirubin will go to the liver and it cannot excrete the bilirubin as quickly as it is formed.

Hepatocellular Jaundice – it is caused by inability of damaged liver cells to clear normal amounts of bilirubin from the blood. Damaged liver cells may be from infection (viral hepatitis), medication or chemical toxicity or from excessive alcohol intake.

Obstructive Jaundice – it is caused by occlusion of the bile duct by a gallstone, an inflammatory process, a tumor or pressure from an enlarged organ.