IEEE Spectrum September, 2016 - 12

Three
Ways To
Build an
arTificial
Kidney
Three research groups taking
very different approaches to building an artificial kidney all have the same
goal: giving people with kidney failure
an escape from today's dialysis routine.
Dialysis keeps people alive, but it's also
pretty terrible.
A typical patient goes to a clinic three
times each week to be hooked up to a
dialysis machine, then lies there for
3 or 4 hours while blood cycles out of
the body, through the machine, and
back in again. The machine substitutes for working kidneys by filtering
out toxic waste products, maintaining
the balance of electrolytes, and removing excess water.
In addition to losing time and mobility, most patients have to carefully
restrict their diets and fluid intake to
stay healthy between sessions. Patients
also deal with a host of side effects,
says Steven Weisbord , a kidney specialist at the University of Pittsburgh
School of Medicine. His studies have
documented downsides that include
extreme fatigue, depression, low blood
pressure, and muscle cramps. "It is a
lifeline for patients," Weisbord says,
"but [dialysis] is associated with signif-

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icant decrements in quality of life and
bothersome symptoms."
Here are three ideas that might lead to
a better way.
Kidney-on-a-Belt
The wearable artificial kidney, or WAK,
looks rather like a bulky utility belt. In
a recent clinical trial, patients wore the
WAK for 24 hours of continuous treatment, with mixed results. Technical
problems halted the study early, but
the inventors say those problems are
fixable, and they stress that the device
provided both effective treatment and a
better quality of life for the test subjects.
In typical dialysis machines, blood
f lows into a tube called the dialyzer,
where waste particles pass through a
membrane into a solution that carries
them away. Fresh solution continuously
flows into the dialyzer. On the 5-kilogram
WAK belt, the solution cycles through a
miniature dialyzer and then back to cartridges where the toxins are absorbed so
the solution can be cycled through again.
During the 24-hour test, conducted by
researchers at the University of Washington and the University of California, Los Angeles, the battery-powered
wearable device cleared toxins from the
blood as effectively as a typical dialysis
machine does.
The trial subjects' experience suggests
that the WAK can improve quality of

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life, as they could walk around or sleep
during treatment. They could also eat
and drink whatever they wanted, unlike
ordinary dialysis patients.
However, the technical problems
were significant: The trial's seven participants encountered kinked tubes, an
erratic pump, and batteries and absorbent cartridges that needed replacing.
Most important, gas bubbles were found
in the WAK's solution circuit, which can
be deadly if they reach the heart or brain.
The device includes bubble alarms and
degassing vents, but the researchers
plan a redesign to reduce gas production and improve venting.
The WAK will have to operate f lawlessly to fulfill the ultimate goal stated
in the researchers' journal article in
JCI Insight: "for treatment with the WAK
to be self-administered independently
by patients and caregivers in the home
environment."
The Cyborg Kidney
Researchers from the University of California, San Francisco, and the Cleveland Clinic, in Ohio, started the Kidney
Project in 1998 to build a "bioartificial"
kidney that combines mechanical and
biological parts.
The implantable device is about the
size of a coffee cup. Blood first flows into
a filtering unit that draws waste particles and other molecules through a sili-

stePhen Brashear

wearable, implantable,
and bioartificial kidneys
could improve and extend
patients' lives

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Table of Contents for the Digital Edition of IEEE Spectrum September, 2016