Jaundice (from French "jaun" meaning "yellow", aka icterus) is yellowish pigmentation of the skin, conjunctiva, and other mucous membranes.
What does jaundice mean? It sounds like someone who's being a bit of a joker !
Jaundice means that your skin and mucous membranes have become yellowish.
Bilirubin is a waste product formed when old RBC's break down, and is usually removed by the liver. Jaundice is caused by hyperbilirubinemia (raised bilirubin in blood, as it is unable to be removed by the liver which is too immature or sick), which subsequently increases bilirubin in the extracellular fluid, causing the yellowish pigmentation. It is classified into:
Pre-hepatic (hemolytic), where the pathology is occuring prior to the liver, specifically, increasing the rate of hemolysis (breakdown of RBC). Bilirubin is the yellow breakdown product of normal heme (principal component of RBC) catabolism. Examples include:
Certain genetic diseases, including sickle cell anemia, spherocytosis, thalassemia, G6PD deficiency
Kidney disease, e.g. hemolytic uremic syndrome
Defects in bilirubin metabolism, e.g. Gilbert's syndrome (i.e. genetic disorder of bilirubin metabolism)
Hepatic (hepatocellular), where the pathology is located in the liver. Examples include:
Hepatitis (acute or chronic, including drug induced)
Alcoholic liver disease
Post-hepatic (cholestatic, obstructive), where the pathology is located after the liver (where bilirubin is conjugated), specifically, an interruption to the drainage of bile (containing conjugated bilirubin) in the biliary system. Patients often complain of an itch due to depositon of bile salts. Examples include:
What makes your skin yellow?
It's caused by bilirubin, which diffuses out into the skin, making it yellow. This in turn caused by high levels of bilirubin in blood. We divide the causes into problems before, at, and after the liver.
What is bilirubin?
Bilirubin is a breakdown product of heme, in red blood cells. It is excreted into bile, urine, and feces. Which is what makes these things yellowish.
So what are these before, at and after liver problems, that cause high bilirubin in blood?
Before the liver, means there's increased bilirubin coming in, which only happens because more red blood cells are being broken down, which is called hemolysis. This can be caused by blood diseases, kidney disease. At the liver, is anything and everything that can go wron giwht th eliver, like inflammation, metabolism of something toxic, scarring of liver tissue, alcohol damage. After the liver, is problems with draining of the bile. So it's something obstructing, like a gallstone, or pancreatic cancer.
Oh wow. That sounds very similar to kidney injury, which you divide into stuff before, at, and after the kidneys, and it's also problems with blood, problems with the kidney itself, and obstruction of the urinary tract!
Blood bilirubin, is usually <1.2 mg/dL (<25µmol/L), and when >2.5 mg/dL (>50µmol/L) leads to jaundice: -> note that the threshold for bilirubin to cause jaundice in babies is 2.5x HIGHER, as it is more normal to have higher bilirubin as a baby
Increased unconjugated bilirubin in blood, since the liver is unable to conjugate with sufficient speed
No bilirubin in urine, since unconjugated bilirubin is water insoluble
Increased urobilinogen in stool, because the bile duct is not obstructed, so bilirubin has access to the intestine (where bilirubin is converted to urobilinogen). The exception is in infants where gut flora hasn't developed
Bilirubin in urine, since conjugated bilirubin is water soluble
Increased urobilinogen in stool, per above
No urobilinogen in stool, since bilirubin has no access to the intestine (where bilirubin is converted to urobilinogen), in complete obstruction of the bile duct. Stools arepale due to lack of (intestinal) urobilinogen
Increased conjugated bilirubin in urine, because there is conjugation in the liver. Urine isdark due to conjugated bilirubin in urine
What makes you say someone is yellow due to high bilirubin?
When bilirubin in blood is higher than a particular level.
How do you tell the difference between pre-hepatic and hepatic?
That's pretty straightforward, because the liver conjugates bilirubin. So pre-hepatic is going to have more UNconjugated bilirubin, because the liver is unable to conjugate with enough speed. Because conjugated bilirubin is water soluble, but UNconjugated bilirubin is water INsoluble, hepatic is going to have more conjugated bilirubin, which makes it darker.
How about hepatic and post-hepatic?
Because there's a blockage in the access of bilirubin into the intestine, where bilirubin is converted into urobilinogen and stercobilin, there's NO urobilinogen.
Yellow discoloration of the skin of the palm and soles, but not of the sclera and other mucous membranes (e.g. oral cavity) is due to carotenemia (excess intake of carrots)
Discoloration can also be caused by side effect to using the drug mepacrine, or excessive exposure to phenols
Why else can you be yellow?
Because you're eating too many carrots .
Prognosis is excellent if appropriate monitoring and Tx is provided. Most wil improve with no adverse effects
Nonetheless it is important to consider potential dangers of severe hyperbilirubinemia, to prevent devastating consequences of kernicterus
Is there any problem other than looking like you've had an awful spray tan?
Too much bilirubin in blood, can cause it to accumulate in the grey matter of the brain, which can cause irreversible brain damage. That's called kernicterus.