Why is it possible to perform a liver transplant using just a small part of a donor’s liver, but for other organs (kidney, heart, etc) the donor would have to donate the whole organ?
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AFAIK, the simple answer is a healthy liver can regenerate a single lobe or two as the liver can be broken down fractionally. Kidneys and hearts and etc, aren’t able to be fractional organs and be viable for transplant. It’s all or nothing.
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Like others say, the liver is magic in how it can regenerate, but ALSO the liver is magic in how efficient and effective it is. Generally you can lose up to 80% of your functional liver cells before you start feeling and being ill. In that same way, as little as 20% of a liver needs to be transplanted to give sufficient function to survive.
Edit: kidneys are also pretty amazing with how much function they can loose before things get serious, but because they can’t regenerate and are more fragile like, you need to transplant a whole one or nothing. Good thing we have two!
Your liver main deal is to eat up all the poison in your blood and get rid of it.
With a job like that it ended up needing to be really good at dying and growing back. So it’s special among organs that it is really good at not having much structure and growing back from any part left. So you can just throw any part in someone and it will try hard to turn back into a liver
Basically most organs are made up of permanent tissues whose cells can not regenerate at all, whereas the liver’s tissue is known as stable tissue which does have the ability to replicate but only in response to injury i.e cutting a part for a transplant. Note that stable tissues have minimal ability to replicate but the liver is the exception and has a great ability to regenerate about half of its full form. Why is the liver the exception? That I do not know.
Besides what people are saying about the regenerative nature and efficiency of the liver, the main reason the liver can be subdivided is that it recieves blood supply from two sources. A single lobe had enough available plumbing to tie into another system.
One thing a doctor friend once told me is that some organs have literally ZERO healing ability… like the kidneys. Any damage done to them persists for the rest of that organs lifetime. Some have marginal healing, like lungs, that can slowly repair smoking damage over the course of a few years.
The liver is made of connective tissue and while the shape of the left and right is a little different, it largely does the same thing. Skin is also an organ made of connective tissue and can also be partially transplanted.
Other organs have a shape that is essential to their function. The heart pumps blood from atrium to ventricle in a series, if you tried to take half of it, it wouldn’t work. It has specialized parts that work together and can’t function without them.
Sorry, gonna have to be a bit crass here for clarity. Does half a pump work correctly, or half a filter? No. Hearts and kidneys are composed of discrete structures that work together as a biological machine. So transplanting a portion of one simply doesn’t work; also, while you can grow heart or kidney tissue, growing back fully-differentiated tissue structures is another matter entirely (though kidneys have been known to sometimes regrow a bit if inadvertently damaged when the owner is young), so even if you were to transplant such a partial organ, and it somehow managed to function, there no chance that said organ would completely regenerate, let alone regenerate correctly. The liver, by contrast, is effectively composed of a single undifferentiated (even though the organ itself structurally has lobes) tissue type, and, as such, can function correctly even as a small(er) piece when transplanted, and can also grow back in time.
With kidneys, it’s convenient that there are two, and a single functional kidney is enough to keep you off dialysis.
If you had two livers they would take one of them, but you don’t. So if there is a living donor, they have to take part of it. The remaining part of the liver and the donated part of the liver will regenerate, within limits.
Part of a heart is not functional. So they have to take the whole thing, and you cannot have a living donor.
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