Now, imagine for a second that somebody's kidneys suddenly stopped working, which we call kidney failure. What things do you think might happen? Well, the main consequences would be that waste substances would build up in their bloodstream, and also that the person would be unable to regulate their water and ion levels. Because of this, the person would quickly become sick, and if they weren't treated, then they could even die. Although mild kidney disease can be treated with medication, the only treatment for kidney failure is dialysis or a kidney transplant.
Let's start with dialysis. Dialysis machines are effectively artificial kidneys which can filter a patient's blood for them. So even if theirs doesn't work properly, their blood is still getting filtered. For the sake of understanding, we can use this diagram here to understand how they work.
Once a nurse has connected the patient's blood supply to the dialysis machine, their blood can pass into the machine, through the circuit, and then back out into the patient. While it's in the machine though, the patient's blood comes into contact with the dialysis fluid, but importantly, they're separated by a partially permeable membrane. which means that small molecules, like water and ions, can diffuse across, but bigger things, like cells and proteins, can't.
The important thing about the diaseous fluid is that it's a mixture that contains the same concentrations of water and other molecules as healthy blood does, so it would contain a reasonable quantity of glucose, ions, and amino acids. but no urea because healthy blood doesn't have any urea in it. This means that if the patient has too much of anything, like too many ions or too much water, they will diffuse across the partially permeable membrane into the dialysis fluid because there'll be a concentration gradient and that will bring the patient's blood levels back down to normal. The problem with this is that after a while it would reach equilibrium. and nothing would diffuse anymore.
So to prevent this, the dialysis fluid is constantly replaced, with new fluid being pumped in from the bottom and older fluid passing out of the top. And this means that there's always a concentration gradient so that we lose all of the things from the blood that we don't want. So to summarize all of this, as the patient's blood passes through the machine it loses all of the junk that it doesn't want. like any extra ions or amino acids, and pretty much all of the urea.
And once it's passed through, it's then much cleaner and can go back into the patient. Now, as great as this sounds, there are some problems with dialysis. One is that the treatment is very time consuming. Patients have to go into hospital three to four days a week. and be hooked up to the machine for 3-4 hours each time.
It's also an unpleasant experience, and can cause problems like blood clots or infections. The last issue is that it's very expensive to run, and people will have to have it continually for the rest of their life. An alternative to dialysis is a kidney transplant. This is a surgical procedure, where we take a healthy kidney from one person and transfer it to a patient that needs it. Most of these donated kidneys come from people who have recently died, but living people can also donate a kidney, as we're all born with two of them but can live perfectly well with only one.
As with any surgery, there is a small risk that something will go wrong, but the main risk for the patient is that the organ will be rejected. Rejection is when a transplanted organ is attacked by the patient's own immune system, which treats it as a foreign object, and so wants to destroy it. Doctors do help by giving patients medication to suppress their immune system, but unfortunately it doesn't always work.
Overall, even though transplants tend to be better and much cheaper than dialysis, There's just not enough available organs to give everybody a transplant, and so loads of people still have to rely on dialysis. Anyway, that's everything for today's video.