Polycystic Kidney Disease
Polycystic kidney disease, or PKD, usually
refers to a genetic or inherited disease that is sometimes
called "adult PKD" because it normally appears in adult life. A
less common type of PKD occurs primarily in babies and children.
In PKD, cysts, or fluid-filled pouches,
are found primarily in the kidney but they can also affect other
organs, including the liver, pancreas, spleen and ovaries.
Outpouchings may occur in the walls of the large intestine and
in the walls of blood vessels in the brain, where they may cause
aneurysms. They may also be found in the abdominal wall, causing
hernias. In addition, the valves of the heart may be involved,
becoming floppy and resulting in a heart murmur in some
patients.
How common is PKD?
PKD is the most common life-threatening
genetic disease. Scientists estimate that it affects between one
in 400 and one in 1,000 individuals. It is found in all races
and occurs equally in men and women.
Who is at risk for developing PKD?
The adult type of PKD (also called
autosomal-dominant PKD or ADPKD) is passed from parent to child
by an autosomal-dominant type of inheritance. This means that
only one copy of the abnormal gene is needed to cause the
disease. Therefore, if one parent has the disease, each child
has a 50-50 chance of getting the disease. The risk is the same
for every child, regardless of how many children develop the
disease.
The less common form of PKD (also called
autosomal recessive PKD or ARPKD) is passed by an autosomal
recessive pattern of inheritance. This means that both parents
carry the abnormal gene, and both must pass the gene to the
child in order for the child to get the disease. In this
situation, every child has a 25 percent chance of getting the
disease in a family that is at risk.
What are the clues that someone has PKD?
People who have inherited ADPKD often do
not notice anything unusual until they are 30 to 40 years old.
The first noticeable symptoms may include:
- high blood pressure
- back or side pain
- an increase in the size of the abdomen
- blood in the urine
- frequent bladder or kidney infections.
High blood pressure is the most important
treatable risk factor in PKD. Occasionally, patients may develop
headaches related to high blood pressure or their doctors may
detect high blood pressure during a routine physical exam.
Finally, about 25 percent of PKD patients have a so-called
floppy valve in the heart, and some of these develop a
fluttering or pounding in the chest as well as chest pain. These
symptoms almost always disappear on their own but may be the
first hint that someone has PKD.
How is PKD diagnosed?
Today, ultrasound is the most reliable,
inexpensive and non-invasive way to diagnose PKD. If someone at
risk for PKD is older than 30 years and has a normal ultrasound
of the kidneys, he or she probably does not have PKD.
Occasionally, a CT scan (computed tomography scan) may detect
smaller cysts that cannot be found by an ultrasound.
At present, PKD cannot be diagnosed by a
single blood test. However, in some situations where it is
important to have a diagnosis (for example, if a family member
wants to donate a kidney to an affected parent or sibling, and
ultrasound and CT scans are normal), special blood tests on at
least three family members can be done to get a diagnosis in the
at-risk individual. This form of testing is called gene linkage
analysis.
Does everyone with PKD develop kidney
failure?
No. About 50 percent of patients with PKD
will have kidney failure by age 60, and about 60 percent will
have kidney failure by age 70. Certain people have an increased
risk of kidney failure including:
- men
- patients with the most common form of
PKD (ADPKD)
- patients with high blood pressure
- patients with protein or blood in their
urine
- women with high blood pressure who have
had more than three pregnancies.
How is PKD treated?
At present, there is no cure for PKD,
although a lot of research is being done. Many studies suggest
that some treatments may slow the rate of kidney disease in PKD,
but further research is needed before these treatments can be
used in patients. Other studies are improving our understanding
of the genetic basis of PKD.
In the meantime, many supportive
treatments can be done to help prevent or slow down loss of
kidney function in PKD. These include:
- careful control of blood pressure
- prompt treatment of a bladder or kidney
infection
- lots of fluid and bed rest when blood
in the urine is first noted
- a healthy lifestyle with regard to
smoking, exercise, weight control and salt intake.
Should people with PKD take a special
diet?
At present, no specific diet is known to
prevent cysts from developing in patients with PKD. Reducing
salt intake helps control blood pressure in PKD patients who
have high blood pressure. Low fat and moderate caloric intake
are recommended to avoid becoming overweight.
Is exercise recommended for people with
PKD?
Absolutely. However, exercises that are
potentially harmful to the kidney, such as contact sports,
should be avoided. It is important not to become too dehydrated
during any physical activity.
See also in this A-Z guide:
- How Your Kidneys Work
- Warning Signs of Kidney and Urinary
Tract Diseases
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