Bionic Kidney: The Important Innovation That Could Reduce Transplant Waiting lists

standard dialysis LCD monitor

The bionic kidney technically classified as a bioartificial kidney promises a future free from the risks of transplant waiting lists.

Artificial kidneys, as you might already know, are one of the most important components of any critical care system. It is a modern medical convenience that dates back as early as the 1940s, when a Dutch physician named Willem Kolff invented the very first type of dialyzer.

Museum Boerhaave Kolff's Artificial Kidney
Image credit by rob koopman via Flickr

As revolutionary as they have been in the development of modern life support technologies, the lack of any method to perfectly integrate them into the human body has always been their greatest limitation. Unlike devices such as pacemakers and ocular implants, dialysis machines always need to be separate and outside the body, even if they have evolved to be as portable as a strap-on belt.

The only exception is a bionic kidney. More technically classified as a bioartificial kidney, it promises a future free from the risks of transplant waiting lists, and is unbound by the very limitations that traditional dialysis technologies just cannot escape from.

Artificial kidneys and dialysis quick recap

Artificial Kidney Dialysis process
Image credit by wistechcolleges via Flickr

In a nutshell, a standard hemodialysis process starts by joining a vein and artery on your arm together to form a stronger blood vessel. This is so that it can withstand the process of connecting to the machine along with the stress of continuous external blood flow.

Once the needles have been struck and the tubes connected, the dialysis machine then pumps blood into several membranes that filter the typical waste products the kidney would usually deal with. Afterward, the filtered blood is then pumped back into the body, and the waste products pass into a dialysate fluid, where they are removed from the dialysis machine.

Conceptually, it’s exactly the same as a natural kidney. But as you may have already guessed, they are never perfect due to a few built-in limitations:

The patient must be strapped to the machine the entire time. This not only limits movement but also makes any interruptions a huge hassle. If you are connected to automated peritoneal dialysis (APD) machine, for example, and you need to go to the toilet, you need to manually disconnect and reconnect everything.

Dialysis creates occasional unintended side effects, partially to the intermittent nature of the procedure. The most common is lightheadedness. There is an external source that manipulates the blood fluid levels in your body, after all, as opposed to being balanced automatically by the body.

The machine can’t provide a one-to-one efficiency rate with a real kidney. Even with the best artificial kindeys, daily sessions can only filter out limited amounts of blood waste products per unit of time. Doctors would usually prescribe significantly reducing your fluid intake when using the dialysis machine. You might also need to carefully watch your sodium, potassium, and phosphorus levels, as these are far more difficult to filter out artificially.

The miracle of wearable artificial kidneys?

bionic kidney being tested
Image credit by the National Kidney Foundation / National Library of Medicine

Thus, the idea of wearable artificial kidneys inevitably came to life. The advantages of such a straightforward concept are plain and obvious. It effectively eliminates the first disadvantage of constant connection, allowing it to be a permanent augmentation of sorts, giving us the opportunity to finally classify it officially as a “bionic” device. Heck, the relative efficiency might not even matter much, since its operation can’t be interrupted by momentary disconnection.

Unfortunately, that’s actually the biggest challenge for wearable artificial kidneys. First and foremost, the weight of the entire system must be negligible enough for regular use. Something like the revolutionary artificial kidney belt prototype developed by a team of researchers at the University of Washington Medical Centre could work. But it needs to be shrunk further to solve both its weight issues and its risk of being an obstacle for both its users and the people around them.

Another challenge related to constant use is the potential side-effects of the device’s continuous operation. If temporary use already causes dizziness due to the changing fluid levels in the bloodstream, imagine what would happen if the device becomes a permanent attachment that operates 24/7.

Lastly, all typical limitations of portable electronic devices would also apply to any wearable artificial or bionic kidney. How exactly is it powered? How long can it stay on? Would the operational efficiency of the machine be sacrificed upon miniaturization? Batteries would also add to the overall weight and mass distribution of the portable dialysis machine.

How bionic kidneys transcended via usability and deployment issues

As an ultimate answer to these challenges, the final step of creating an implantable artificial kidney seems to be the one and only true answer. To this end, bioartificial or bionic kidneys are primarily designed the same way as an artificial heart: to replace kidneys in the exact same position, both functionally and positionally.

Conceptually, bionic kidneys easily run past the issue of continued operability by being small and very efficient. However, as you may have already instantly realized, the effort to miniaturize the technology several times further already poses another set of nearly impossible challenges for researchers. Hence, why even today, bioartificial kidneys remain an idea on the drawing board.

That is, until several prototypes finally started popping up over the last few years. The Kidney Project, a collaborative effort that originated as a research paper in 2016, is perhaps the most prominent of them all. This is because the biggest limitation in portable dialysis machines happens to be its most important innovation: the development of filtering membranes that rely solely on the body’s natural internal blood pressure.

Artificial bionic kidney operation process explained
Image credit by Dr. Shuvo Roy et al

The prototype consists of two major components, a hemofilter and a bioreactor. When the bioreactor’s renal tubular cell production is combined with high-level nanofrabrication technologies, it can almost perfectly mimic the way compounds are naturally taken out or absorbed by the kidney. This is all without the use of any external power whatsoever.

The physical device is no larger than a coffee mug, and has undergone clinical trials last year under the official name IHemo. The tests from the overly simplified prototypes were eventually found to be highly successful, earning the team an award from KidneyX for being the first-ever research group that has successfully demonstrated a functional implantable artificial kidney.

While the IHemo has only been tested thus far on pigs, the concept alone is presumably enough to launch bionic kidney technologies into eventual practical use in only a few decades. Especially the idea of passive energy use, as well as using reinforcing what is already naturally done (via renal tubular cells) by strategically-designed hemofilters.

The race against organ regeneration technologies

One final wild card to add to the march of progress toward the development of true bionic kidneys is the research done in organ regeneration. It has been known for a while that stem cells can theoretically be cultured externally to be developed into various organs for each user. However, several very important hurdles, such as training the newly developed cells, are yet to be solved.

Bionic kidneys may not be the endpoint within this particular field of medicine. But it is very possible that it could be a bridge to close the time gap between the advancement and maturity of organ regeneration technologies. After all, if perfectly customized organic kidneys are on the menu, why even settle for an artificial one?

This, of course, includes the transplant waiting list. Because in the next decade or two, people with the end-stage renal disease could simply opt to use a bionic kidney to return to their normal lives, while they still wait for that fresh new organ to arrive.

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