A wearable artificial kidney is a wearable dialysis machine that a person with end-stage renal disease could use daily or even continuously. As of November 2008, no wearable kidney is widely available, but many research teams are in the process of developing such devices (see below).

History & motivation

Chronic Kidney Disease (CKD) affects 26 million people in the United States, and around 400,000 of these patients have end-stage renal disease requiring dialysis or transplantation. The mortality rate for patients with end-stage renal disease is around 22% per year, and at the moment, dialysis is the only therapeutic option for these people. Dialysis therapy is usually given three times a week for four hours at a time, and it involves many risks such as bleeding, clotting, and infection. For patients and society in general, the emotional and financial costs of dialysis therapy are very high. The quality of life for patients on dialysis is often very low, and the yearly cost of treating end-stage renal disease is around $27 billion.

The ideal wearable kidney would mimic the function of the kidneys by providing:

1. continued dialysis (to avoid the sudden electrolyte disturbances associated with timed dialysis), and
2. be effectively autonomous so that little to no patient intervention is necessary.

Methods of implementation range the same spectrum as traditional dialysis. Experiments have been carried out since the seventies, and included miniature hemofilters utilizing REDY cartridges or by drinking dialysate. The development of continuous ambulatory peritoneal dialysis was successful and significant achievement, but it requires significant patient intervention.^[1][2]

Technology

Today?s dialysis machines are far from perfect. Their efficiency is only around 10% of that of a functioning kidney, and when used three times per week, they are incapable of controlling unhealthy fluctuations in the concentrations of metabolites such as urea in the blood. Many researchers are seeking to design an artificial, wearable kidney that would make dialysis a more effective therapy.

Nanotechnology offers enticing possibilities in this area. Thin nanomembranes would be more permeable to solutes in the blood than thicker conventional membranes, and these nanomembranes could be carefully engineered to contain highly selective pores, instead of the randomly sized pores present in membranes used today. Particular pores, forexample, could be designed to selectively filter middle-sized molecules from the blood. Some middle-sized molecules, such as beta-microglobulin, can cause debilitating health problems when they accumulate in the body, and traditional dialysis machines do a poor job of filtering these molecules from the blood. Eventually, researchers hope to create a library of engineered pores that would allow nephrologists to come up with customized dialysis regimens specifically tailored to their individual patients.

Devices in development

Researchers in Italy have developed a semi-autonomous system called the Vicenza Wearable Artificial Kidney for Peritoneal Dialysis (ViWAK PD). The ViWAK PD is a fully-electronic system with a belt and waterproof chamber that houses the replaceable sorbent tubes. Patients replace the sorbent cartridges a couple times a day on a schedule in conjunction with overnight peritoneal dialysis. Patients can monitor and control their therapy wirelessly via a handheld remote or a computer.^[3] In 2008, researchers at UCLA detailed a peritoneal-based AWAK that can provide continuous filtration, mimicking the functions of the normal kidneys. The system would never need patient intervention except during cartridge replacement every 8 or 12 hours. This device is able to regenerate and reuse fluid, and protein components in the spent dialysate - the fluid that has extracted toxins from the patient through the peritoneal cavity, and which is discarded in current, traditional dialysis protocols. The regenerated dialysate is pumped into the patient for the next cycle of dialysis. As such, protein loss is minimized or eliminated and minimum amount of dialysate is required, making a wearable kidney possible.^[4][5] The technology has been licensed for production.^[6]

An artificial kidney design from XCorporeal, Inc. passed preliminary tests in a recent pilot study. It utilizes sorbents to regenerate the dialysate and thus afford a considerable reduction in the amount of dialysate required for each treatment. Waste products in the dialysate are removed by passage through a column of sorbent resulting in the regeneration of fresh dialysate. This study was completed in 2007 with Dr. Andrew Davenport at the Royal Free Hospital, London in the United Kingdom, and demonstrated the feasibility of a small, wearable, self-contained hemodiafiltration system.^[7]

References

Conference references

• CIMIT Forum. January 15, 2007.

Video references

• Impact of Chronic Kidney Disease Joseph Bonventre, MD, PhD, Harvard Medical School
• an Artificial Kidney Theodore I. Steinman, MD, Harvard Medical School
• a Wearable Kidney to Market Greg Erman, MBA, former president and CEO of Renalworks Medical Corporation
• an Artificial Kidney Jeffrey Borenstein, PhD, Drapers Labs

Additional video references

• Panel Discussion on Wearable Kidney CIMIT

External links

• CIMIT Center for Intigration of Medicine and Innovative Technology

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