Download Polycystic kidney disease - The Kidney Foundation of Canada

Polycystic
kidney
disease
THE
KIDNEY
FOUNDATION
OF
1
CANADA
Polycystic kidney disease
n What is polycystic
kidney disease?
Polycystic means “many fluid-filled sacs”
or “many cysts”. Polycystic kidney disease
(PKD) is a genetic disorder that causes
multiple cysts to form in the kidneys.
n What are the kidneys?
The kidneys are the master chemists of the
body. Normally, there are two of them, one
on either side of the spine under the lower
ribs. They are reddish brown in colour and
shaped like kidney beans. Each kidney is
about the size of your clenched fist. Many
other organs depend on the kidneys in
order to work properly.
Renal
artery
Renal
vein
Kidneys
Ureters
Bladder
Urethra
LOCATION OF THE KIDNEYS
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n How does PKD affect
the kidneys?
Polycystic kidneys become very large, have
a bumpy surface and contain many fluidfilled cysts.
This can be associated with a number of
conditions, including:
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High blood pressure
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Urinary and kidney infections
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Kidney stones
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Kidney failure
Kidney failure resulting from PKD is caused
by a combination of:
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Pressure from expanding cysts,
compressing normal kidney tissue
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Scarring in the normal support tissue
in the kidney
n Who is affected by PKD?
PKD can strike anyone at any time. About
5% of all people requiring dialysis or kidney
transplantation have PKD.
n How do you get PKD?
PKD is an inherited disease. This means
that it is passed on from parents to their
children. Everyone has 23 different pairs of
chromosomes, with one set coming from
each parent. Chromosomes are scaffolds
that carry individual hereditary units called
genes. Genes are programmed to produce
proteins. Proteins are the structural and
functional building blocks that enable
individual cells to work properly.
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n Are there different forms
of PKD?
There are two forms of PKD: autosomal
dominant PKD (ADPKD) and autosomal
recessive PKD (ARPKD).
Autosomal dominant PKD is the most
common form of the disease. It affects
about 1 in every 1,000 births and symptoms
usually appear in midlife. ADPKD follows a
dominant inheritance. This means that if
either your mother or father has ADPKD,
you will have a 50% chance of inheriting
ADPKD. If the gene for ADPKD is not
passed on, you will neither inherit the
disease, nor be able to pass on the disease
to future offspring.
ADPKD is not a single
disease. There are at
least two genes that
are associated with
ADPKD. The Type 1
variant occurs when
you inherit a defective
copy of the PKD1 gene
on chromosome 16.
This form of disease
accounts for about
85% of all cases of
ADPKD. The Type 2 variant occurs when
you inherit a defective copy of the PKD2
gene on chromosome 4. This form of the
disease accounts for most of the remaining
cases. Generally, the symptoms of both of
these subtypes overlap completely.
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Autosomal recessive PKD is a very rare form
of PKD causing symptoms in infants and
young children. You may develop ARPKD
if each of your parents carries at least one
defective copy of the disease gene; in this
case, you have a 25% chance of having
the disease. If only one parent carries the
defective gene, you cannot inherit the disease.
n What are the chances that
PKD will cause kidney failure?
Kidney failure occurs when you are left with
less than 10-15% of total kidney function.
When the kidneys fail, dialysis treatment or
a kidney transplant is needed.
Not everyone with PKD will go on to
develop kidney failure. On average, half
of the people with the Type 1 variant of
ADPKD will require treatment for kidney
failure by age 60. However, people affected
with the Type 2 variant have a lower risk
for developing kidney failure. There are
treatments available that help to delay
progression of ADPKD.
Children born with ARPKD usually develop
kidney failure within a few years.
n What are the symptoms
of ADPKD?
ADPKD usually progresses very slowly. Early
in the disease there are often no symptoms.
The only way to detect ADPKD is to be
tested for cysts in the kidneys.
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The most common symptoms of ADPKD
include:
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Pain in the back and the sides
(between the ribs and hips)
n
Headaches
People with APKD may also experience
the following:
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High blood pressure (hypertension)
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Urinary tract infections
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Blood in the urine (hematuria)
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Kidney stones
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Liver and pancreatic cysts
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Abnormal heart valves
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Bulges in the walls of blood vessels
in the brain (aneurysms)
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Small sacs on the colon (diverticulosis)
n How is PKD diagnosed?
The main method used to diagnose PKD is
an ultrasound. This test uses sound waves
to generate echo patterns to detect the
presence of cysts. The ultrasound can show
both the number and size of individual
cysts in the kidney and liver. You might also
be referred for a CT scan, a method that
uses X-rays to detect very tiny cysts.
Another method of diagnosis is called gene
linkage analysis. Blood tests from family
members can be used to detect which
family member carries the PKD gene. This
method, however, requires availability of
DNA from multiple affected members of
the family, and is not routinely done for
diagnostic purposes.
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More recently, direct genetic testing for a
mutation on the PKD1 and PKD2 genes is
being used to diagnose autosomal dominant
PKD. Using this testing, ADPKD can be
detected before cysts start to develop.
Before you consider being tested for PKD,
it is important to discuss with your doctor
the benefits and risks involved. These can
include determining the possibility of
having a child with PKD, and what the
test results might mean to career and
insurance discrimination.
n What should you do if
you have PKD?
Although a cure for PKD is not available,
significant progress in research of PKD
has been made and novel treatments are
available to ease symptoms and delay the
progression of the disease.
A person with PKD should:
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Visit their doctor regularly.
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Learn all they can about the disease.
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Control high blood pressure.
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Have urinary tract infections treated
immediately.
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Never take any over-the-counter
medication without first checking
with their doctor.
n
Discuss family planning with their
doctor or genetic counselor.
T h e K i d n ey Fo u n d a t i o n
OUR VISION
Kidney health, and improved lives for all
people affected by kidney disease.
OUR MISSION
The Kidney Foundation of Canada is the
national volunteer organization committed
to reducing the burden of kidney disease
through:
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funding and stimulating innovative
research;
providing education and support;
promoting access to high quality
healthcare; and
increasing public awareness and
commitment to advancing kidney health
and organ donation.
For further information, or if you wish
to help us in our efforts, please contact
The Kidney Foundation of Canada office
in your area. You can also visit our Web site
at www.kidney.ca.
With acknowledgement to Dr. Michael Copland, Clinical
Assistant Professor, Division of Nephrology, University
of British Columbia and the Vancouver Hospital and
Health Sciences Centre, for his assistance in reviewing
this information.
© 2007
R E F. N O . : E D - 6 0 - 0 0 9 - 0 7
This material is available in accessible
formats upon request by contacting
[email protected] or calling 1-800-361-7494.