Kidneys play a critical and varied role as their complex network of blood vessels, tubes and tubules filter blood off nitrogenous wastes, salts, and excess water. They also regulate fluid and electrolyte levels which may be altered due to drugs or toxins, meaning they are vital for life. However, gradual loss of kidney function owing to diabetes mellitus, hypertension or glomerulonephritis, resulting from genetics and unhealthy lifestyle choices have greatly increased the risk of ESRD(End of stage Renal disease) world wide. For example, In the USA, the age-gender-race adjusted incidence of ESRD is 384.6 per million/year in 2018 while the age-gender-race adjusted prevalence was 2242.1 per million/year in 2018.
People with this life threatening disease need a method to remove fluid, electrolytes and wastes, which may otherwise build up in the body. This can be achieved by Kidney transplantation.
What is Kidney transplantation?
A kidney transplant is a surgery to place a healthy kidney from a living or deceased donor into a person whose kidneys no longer function properly.
Pre surgical procedure
Before receiving a kidney transplant, a person with ESRD must undergo a thorough medical evaluation, including imaging studies, such as X-ray, MRI or CT scans, Blood tests and psychological evaluation to make sure that they are healthy enough to undergo transplant surgery. If the tests prove that they are a good candidate, they are put on a recipient list to receive a kidney from a deceased donor, or more preferably a willing living kidney donor.
Surgical procedure
Once the medical exam deems the patient fit, and an organ is available, and the surgery is performed. The surgeon makes an incision in the lower part of one side of the abdomen and places the new kidney into the body. The barely functioning existing kidneys are left in place, as their removal has shown to lead to serious complications mid-surgery. The blood vessels of the new kidney are attached to blood vessels in the lower part of the abdomen, just above one of your legs (they are usually attached to the iliac fossa).The new kidney's ureter is then anastomosed to the recipient bladder.
Complications
The major disadvantage of kidney transplantation is that the kidney transplant recipients must remain on immunosuppressants for the rest of their life to prevent their body from rejecting the new kidney, which puts them at higher risk for infections due to other diseases and cancer. Other complications include:
Blood clots and bleeding
Leaking from or blockage of the tube that links the kidney to the bladder (ureter)
Death, heart attack and stroke
According to the Scientific Registry of Transplant Recipients, the total number of kidney transplant recipients alive with a functioning graft, including paediatric recipients, exceeded 250,000, reaching 255,738 in 2020.
While kidney transplantation is one of the best forms of renal replacements, it is limited by a significant demand-supply mismatch, with a daily death of 12 patients awaiting transplantation. Moreover, transplanted kidneys also have an average lifespan of 10–20 years, after which the patient needs to restart dialysis when awaiting transplantation, and nearly 60% discontinue treatment due to lack of affordability and care.
These problems have led to the development of a new renal replacement therapy (RRTs), one that aims to give more patient-centric care, i.e artificial kidneys.
What are artificial kidneys?
Artificial kidneys refer to RRTs that are in use and/or in development and are based on applications of enhanced dialysis. Interesting developments have been made in areas such as:
Wearable artificial kidneys (WAKs)
Implantable artificial kidneys(IAKs)
Wearable artificial kidneys(WAK)
Wearable artificial kidneys are essentially dialysers that can be worn by the patient like a belt. This would allow for a patient to be treated 24 hours a day and remain ambulatory, The prototype of the WAK first introduced in 2016 is a 5 kilogram device, running on nine-volt batteries, which connects to a patient via a catheter, and uses less than 400ml of sterile water.
Components
Some of its components include:
Batteries
Pumping systems
Dialysis membrane,
Dialysate regeneration system
Patient monitoring system
While continuous peritoneal dialysis allows a patient to be relatively mobile, it requires large amounts of dialysate to be stored and disposed of. The WAK overcomes the problem as its components include not only a dialysate regeneration system, but also a monitoring system for air bubbles and gas leak in the dialyser circuit, making it a desirable device.
While more research needs to be done in this area, there have been promising leads, such as improved volume control, decreased hypertension and sodium retention, as well as a decreased rate of cardiovascular disease and stroke. The first human trial was conducted by the FDA in 2016. The study aimed to recruit ten patients for dialysis for 24 hours.While only seven enrolled due to technical problems and variable blood and dialysate flow rates. However, there were no adverse hemodynamic changes, target ultrafiltration rates were achieved, and the reasonable patient satisfaction rates were recorded.
Implantable artificial kidneys(IAK)
Titled ‘The Kidney Project’, it is a research project with an aim of developing a small, surgically implantable device that mimics a healthy kidney and performs normal renal function. It is a collaboration between nephrologist William H. Fissell IV, MD, from the Vanderbilt University Medical Centre and Professor Shuvo Roy from the University of California, San Francisco.
Sourced from: The Kidney Project successfully tests a prototype bioartificial kidney · School of Pharmacy · UCSF
Components
The IAK is a confluence of silicon nanotechnology, microchips and tissue engineering. It consists of two parts:
Hemo-cartridge-It is made up of silicon nanopore membranes and replicates glomerular function by processing incoming blood to create a watery ultrafiltrate that contains dissolved toxins as well as sugars and salts) while
Bio-cartridge/Bioreactor- It consists of cultured kidney cells (replicates tubular function, by processing the ultrafiltrate and sending the sugars and salts back into the blood thus maintaining electrolyte balance).
It runs on the patient's blood pressure, and doesn't require dialysate as the bioreactor performs the tubular function and maintains electrolyte balance. The bio-hybrid device will not be in reach of the body's immune response which allows it to be protected against being rejected by the patient's body so there would be no need for immunosuppressants. After successful in vitro and animal studies of the hemo-cartridge, recently, the bioreactor was successfully tested in animals, however the viability of the bioreactor requires further testing.
The research and development of artificial kidneys has exciting prospects—to overcome the problem of an inadequate supply of organs and to provide alternative treatment options that are more patient-friendly, permanent, and affordable—and will hopefully be available in the near future for clinical use.
Written by: Sanjana Meenakshi Yogesh
Glossary
Diabetes mellitus- A metabolic disorder in which the body has high sugar levels for prolonged periods of time.
Hypertension-High pressure in the arteries (vessels that carry blood from the heart to the rest of the body).
Glomerulonephritis- A term used to refer to several kidney diseases (usually affecting both kidneys), characterised by inflammation either of the glomeruli or of the small blood vessels in the kidneys,
Anastomosis- A surgical anastomosis is a surgical technique used to make a new connection between two body structures that carry fluid, such as blood vessels or bowel.
Dialysis- The process of removing excess water, solutes, and toxins from the blood in people whose kidneys can no longer perform these functions naturally.
Catheter- Medical devices that can be inserted in the body to treat diseases or perform a surgical procedure.
Hemodynamics- Hemodynamics explains the physical laws that govern the flow of blood in the blood vessels.
Ultrafiltration-In renal physiology, ultrafiltration occurs at the barrier between the blood and the filtrate in the glomerular capsule where blood pressure and concentration gradients lead to a separation through a semipermeable membrane.
Nephrologist- A person who studies the specialty of adult internal medicine and paediatric medicine that concerns the study of the kidneys.
Glomerulus- A network of small blood vessels located at the beginning of a nephron in the kidney. Glomeruli remove excess fluid, electrolytes and waste from your bloodstream and pass them into your urine.
In vitro- In vitro (meaning in glass, or in the glass) studies are performed with microorganisms, cells, or biological molecules outside their normal biological context.
Bibliography
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