Posts
- What is jaundice or Hepatitis?
- Babies with Jaundice
- What causes jaundice?
- Treatments
Jaundice means the yellow appearance of the skin and whites of the eyes that occurs when the blood contains an excess of the pigment called bilirubin.
Bilirubin is a natural product arising from the normal breakdown of red blood cells in the body and is excreted in the bile, through the actions of the liver.
Although jaundice is most often the result of a disorder affecting the liver, it can be caused by a variety of other conditions affecting, for example, the blood or spleen. It should be thoroughly investigated, so that the underlying cause can be identified and treated.
How does a person get jaundice?
The red blood cells in our circulation carry oxygen to all parts of the body and have a life span of about 120 days. At the end of their life, they are broken down and removed from the circulation by special cells called phagocytes, which are found within the bone marrow, spleen and liver.
New red blood cells are of course continually manufactured, and this also takes place within the bone marrow.
Following breakdown of the red blood cells some of their component parts – such as amino acids and iron – can be re-used by the body. Other components such as bilirubin need to be removed.
Knowing how this removal pathway works is the key to understanding how jaundice occurs.
Most waste products of the body are excreted in the urine via the kidneys, but the liver and bile system is the other main physical route out of the body for these substances.
By 'waste products', we mean the many compounds that arise in the course of the body's metabolism. But almost all forms of drugs must also be eliminated either via the urine or bile routes.
In the case of bilirubin released from old red blood cells, it passes through the bloodstream to the liver, where the liver cells process it.
These cells carry out many complex chemical functions and also produce the liquid bile that is the 'vehicle' by which the cells discharge their output to the bile duct system. This is a branching network of tiny tubes throughout the liver that merge in the same way as the branches of a tree.
Ultimately, a single main bile duct comes out of the liver and joins the first part of the small intestine (duodenum). Bile (and therefore bilirubin) then passes out through the small and large intestines and is excreted in the stool (faeces).
Bile is green in colour. But bacteria in the large bowel act to change the bilirubin to substances that are brown, which gives stool its characteristic colour.
Some of the bilirubin is reabsorbed back into the body through the bowel wall – eventually appearing in the urine as a substance called urobilinogen (although the typical yellow or orange colour of urine is in fact due a different pigment called urochrome).
Therefore, any failure of the bilirubin removal pathway will lead to a build-up of bilirubin in the blood. When this happens the individual's skin turns yellow – causing jaundice.
What conditions can be associated with jaundice?
An excessive breakdown of red blood cells
The balance between manufacture and breakdown of red blood cells is normally precisely balanced and equal. But there are several conditions in which the rate of breakdown increases. If the amount of bilirubin released exceeds the liver's capacity to remove it – jaundice will develop.
The medical term for excessive red cell breakdown is 'haemolysis', and within the developed world it's a fairly rare condition. Malaria is however a major cause in tropical climates because the malaria parasites live within the red blood cells and shorten their life.
Similarly, the condition in which a foetus develops haemolysis, due to incompatibility of its Rhesus blood group with that of its mother, is now rarely seen in the UK – where we routinely check for 'Rhesus antibodies' in the mother's blood. In parts of the world where antenatal care isn't as good, haemolytic disease of the newborn is more common.
A temporary jaundice of newborn babies is however quite common, due to the relative immaturity of the baby's liver cells and the higher than normal rate of cell breakdown that occurs in the first few weeks of life.
It improves rapidly without treatment, although when too high it can be speeded up by exposing the baby to ultraviolet light. Jaundice of the newborn is commoner in premature babies because their liver is even more immature than a baby born at term.
Autoimmune haemolytic anaemia is a rare disease in which the body's immune system seems to attack the red cells. It usually affects adults.
Haemolysis can also be a side-effect of some drugs,
