Sunday, 26 September 2021

Spleen isn’t vital organ but more of a luxury

THE spleen has one of the less appealing names in human anatomy. I often think of it as the Hull or the Slough of the organ world.

Before I get outraged letters from angry Hull or Slough locals though, don’t forget that Hull was 2017 UK City of Culture and Slough has excellent transport links.

My point is that just because the spleen sounds less palatable than some other organs, that doesn’t mean it isn’t useful.

It does tend to go under the radar and probably the most common context in which you’ll hear about it is when it ruptures after an accident.

This has a lot to do with its position in the body. It is a fist-sized organ tucked just underneath the lower left ribs and any blow to this region has the potential to puncture it.

Because the spleen is a very vascular organ — it has lots of blood supply (up to 350 litres pass through every day) — a rupture is bad news and needs emergency intervention. This may result in removal of it altogether (a splenectomy).

In medieval times, at the time of the popular theory of the four humours governing the body’s function (blood, phlegm, yellow bile and black bile), physicians believed that the spleen produced black bile.

This was thought to create bad feelings and short tempers. Someone thought to be giving off fumes from their spleen was said to be “venting their spleen”.

In reality, its vascularity gives us a hint as to its real function. Before we are born, the spleen is responsible for producing red and white blood cells in our blood.

Red blood cells are the disc-shaped cells that are made up of proteins called haemoglobin which carry oxygen through our bloodstream to be used in the body tissues.

The white blood cells (of which there are various types) are focused on fighting infection.

Once we are born, the role of production of our blood cells switches to the bone marrow. This leaves the spleen free to take on more of a filtering role.

Just as the kidneys filter our blood to remove waste products, the spleen filters the blood in order to remove bacteria and viruses and, as such, performs a role in our immune system.

In particular, it helps remove various encapsulated bacteria that have evaded capture elsewhere — those which can cause pneumonia or meningitis.

Once it has isolated these, it kills them by using the various white blood cells it stores in its tissues. In this sense, the spleen is often referred to as a large lymph node.

Lymph is essentially leftover fluid that needs to find its way back into the bloodstream.

The lymphatic system forms a network of channels that help it on its way and a node in this system — like the ones that swell in your neck if you have a sore throat — are checkpoints where white blood cells are stored to fight any germs that are in the vicinity.

This is why your neck is sore when you have a sore throat — the lymph nodes swell as more white cells are activated to fight the infection.

If everything is working as it should, the spleen should not be felt, even if you have a cold.

However, there are various instances where it does need to work a bit harder and can swell.

This may cause a feeling of fullness in your left side or a sense of being full very quickly when eating.

Glandular fever is a common example and is caused by the Epstein Barr Virus. Liver disease can have the same effect and the spleen may also swell up in blood disorders such as leukaemia.

In certain types of leukaemia (a form of cancer that causes abnormal growth of certain types of blood cell), the affected blood cells build up in the spleen and the filtering process may go into overdrive, taking red blood cells out of the system and causing anaemia and removing platelets (which are the cells in the blood that help with clotting the blood – for example, if you cut yourself).

This removal of platelets can cause a propensity to bleed or bruise more easily (thrombocytopenia).

Aside from its role in our immune system, the spleen is also useful in the recycling of red blood cells.

A normal red blood cell has a lifespan of around 120 days after which the spleen removes it from circulation and breaks it down. The products of this are then sent off to other organs like the kidney and liver to be disposed of.

In conditions that affect the shape of red blood cells, such as sickle cell disease, this process can cause problems.

Sickle cell disease is a genetic condition that one gets if both parents carry the defective gene.

It alters the shape of red blood cells from the smooth disc shape into a crescent or “sickle” shape. This causes it to tend to clump together more easily (this can happen in various places around the body and can be extremely painful, not to mention dangerous, and is known as a sickle cell crisis).

It also means the lifespan of the affected red blood cells is much shorter.

The spleen gets rid of these cells after more like 10 to 20 days and, as such, can cause anaemia (low levels of haemoglobin).

In addition, the sickle shape damages the spleen and sufferers will often require splenectomy at quite an early age.

People who have to have their spleen removed become more prone to infections.

For the most part, they can still fight off infections but more serious ones can develop more quickly. In those individuals who are particularly vulnerable, long-term, low-dose antibiotics may be offered.

It is also wise for someone without a spleen to be fully vaccinated. Pneumococcal, Hib (Haemophilus influenzae type b) and meningitis C vaccines are important, as is the annual flu jab.

So, while the spleen performs some exceptionally useful functions, we can get on without it if we have to do so.

Furthermore, the liver can have a reasonable stab at taking over many of the spleen’s functions, so that the spleen is not what you might call a vital organ but rather more of a luxury.

Next time: vaccinations.

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