Feb 20, 2008 11:04 AM

A wearable artificial kidney for
patients on the go

It's light enough to be worn on a tool belt around your waist. You can walk with it, work with it, sleep, take showers — even have sex with it on.

No, it's not an iPod or anything even closely resembling a mobile phone. It's the world's first battery-operated wearable artificial kidney — and it may well be a boon for the millions of people around the world who suffer from kidney failure and must regularly check into a clinic or hospital to purify their blood through dialysis.

Called "WAK" for short, the device has been invented and patented by Victor Gura, an associate clinical professor at the David Geffen School of Medicine.

In clinical trials reported in the Dec. 15 issue of the British medical journal Lancet, five men and three women with end-stage kidney failure successfully dialyzed themselves with Gura's prototype device for up to eight hours.

A typical dialysis machine is the nephrological equivalent of an early computer — bulky, power-sucking machines as big as washing machines. In contrast, the WAK is ergonomically adapted to the body, weighing only about 10 pounds in the initial prototype and equipped with all the devices necessary for dialysis.

Researchers have long been on a quest to develop such a device. "The wearable artificial kidney has been a kind of holy grail that nephrologists have been trying to build for the past 50 years," Gura said. "Lots of attempts have failed."

At the heart of the WAK is a pump that weighs about 17 times less than its counterpart in a conventional dialysis machine. The pump drives blood from a patient through a hollow fiber filter as well as water containing some minerals. The water is constantly purified by circulating through chemicals that capture the impurities that are not removed from the blood anymore because the patient’s own kidneys are failing. The blood is then pumped back to the patient. The filter needs to be replaced about once a week and the chemicals once a day.

"Typically, you require approximately 120 liters of fresh water for a single dialysis treatment," explained Gura, who is the chief scientific officer of Xcorporeal Inc., a Los Angeles-based manufacturer of medical devices that made the WAK. "We use only 375 cubic centimeters of water."

Patients who dialyze daily seem to do a lot better than those who do it three days a week. "The problem is there is not enough money to do daily dialysis, not enough machines and nurses, and patients hate to be on "Treatment of dialysis patients is one of the most expensive items on the Medicare budget."

In the next few months Gura plans to develop a much slimmer product weighing less than five pounds. After further clinical trials, he hopes to make the device commercially available at a cost roughly equivalent to the expense incurred for conventional dialysis and supplies.

"We've spent several millions of dollars already, and it will take a few more to take it to the market," Gura quipped.

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