Polycystic Kidney Disease (PKD) Explained

Polycystic Kidney Disease PKD is a genetic condition that causes numerous cysts (fluid filled sacs) in the kidneys.  The cysts are sometimes found in other organs as well, such as in the liver.  The cysts can grow to be quite large, and in turn cause enlargement of the kidneys. A typical kidney is approximately the size of a human fist, and weighs about a third of a pound.  The kidneys of a person who has PKD can grow to a size as large as a football, and have weighed up to 30 pounds (that's one kidney, at 30 pounds).  The cysts range in number and size, one person may have a few cysts, another person may have dozens. On average cysts can be as small as a pinhead to as large as a grapefruit. 

The cysts cause damage to the kidneys over time, and the kidneys lose their ability to filter waste from the blood effectively.  The loss of kidney function gets progressively worse and can lead to end stage renal disease (kidney failure) which require dialysis treatments or a kidney transplant in order to sustain life.

• Approximately 600,000 people in the United States have PKD.
• PKD is the fourth leading cause of kidney failure
• PKD is responsible for about 5% of all kidney failure. 
• Men and women are equally at risk of having polycystic kidney disease (PKD).

PKD is a genetic disease that is inherited, passed from parents to children. One or both parents may pass the abnormal gene to the child. If one parent has a disease and passes an abnormal gene to a child it is called dominant inheritance.  Each child has a 50% chance of getting the disease. If both of the parents carry the abnormal gene and both pass the gene to a child this is called recessive inheritance and each child will have a 25% chance of getting the disease.   There are two types of PKD, Autosomal Dominant PKD (ADPKD) and Autosomal Recessive PKD (ARPKD) and,  although they both cause the continuous growth of cysts in the kidneys, they are quite different from one another.

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Autosomal Recessive PKD (ARPKD)

Let’s take a look at Autosomal Dominant PKD first, It is the more common of the two types of PKD. Autosomal Dominant PKD (ADPKD) is the most common type of PKD, affecting about 600,000 people in the United States who currently have the disease, and approximately 12.5 million worldwide. 

Causes

This type of PKD is caused by dominant inheritance.  (Only one copy of the abnormal gene is needed to cause the disease). About 90% of all PKD cases are Autosomal Dominant PKD. A person with ADPKD generally does not start showing symptoms of the disease until they are in their 30’s or 40’s.

Symptoms

Since people who have ADPKD often do not develop symptoms until they are well into adulthood, the disease may often be missed until the disease has progressed and damage has already been done to the kidneys.  

High blood pressure is the most common sign of PKD, and high blood pressure can also cause kidney damage. This makes treatment of high blood pressure especially important, the earlier the better.   Treatment of high blood pressure may help to slow the progression of kidney disease, or even prevent the progression to kidney failure.  

Heart valve abnormalities, also known as a floppy valve, occurs in about 25% of people who have PKD.  They may experience fluttering or pounding in the chest, sometimes even chest pain.  These symptoms generally disappear on their own, but can be a clue that the person also has ADPKD.  

Other signs and symptoms may include:

• Back or side pain
• Blood in the urine 
• Urinary tract infections
• Liver and/or pancreas cysts
• Kidney stones

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Autosomal Recessive PKD (ARPKD)

This type of PKD is passed from parents to a child by recessive inheritance, both parents pass on the abnormal gene to the child. This type of PKD is much more rare, it occurs in approximately 1 in 25,000 people.  This type of PKD is very serious, and tends to progress very quickly.  ARPKD has also been called Infantile PKD.  This is because Babies generally showed symptoms of the disease at birth or shortly after and often died within the first year of life.It is much more common for babies born with this type of PKD to survive into adulthood today. However,  they often have developed end stage renal disease by the time they reach adulthood, and require a kidney transplant or dialysis to survive.  It is not unusual for babies to begin developing symptoms of ARPKD before birth, while still in the mothers womb. Ultrasound can  be used and the kidneys often are seen to enlarge in the fetus. Diagnosis then is helpful in preparing the parents for the needs of their child after they are born.  

In some milder cases of ARPKD symptoms may not start to appear until later in childhood. Following are some symptoms seen with ARPKD.

‍Symptoms

• High blood pressure 
• Urinary tract infections
• Liver scarring
• Low blood cell counts
• Stunted growth

People who have PKD and have questions or concerns about having children and passing the disease to them can consult a genetics counselor for guidance.  You can talk to your healthcare provider if you need help with finding a genetics counselor in your area. 

‍Complications ‍

There are some other conditions that people with Polycystic Kidney Disease may be at higher risk of developing.  About 50% of people with PKD will have end stage renal disease (kidney failure) by age 60.  60% will reach end stage renal disease by the age 70.  This will require them to have dialysis or a kidney transplant in order to sustain life.  

Some people with PKD may have increased risk of kidney failure. This includes:

1. Men
2. People with high blood pressure
3. People who have blood or protein in their urine
4. Women with high blood pressure who have had 3 or more pregnancies

PKD may affect other organs besides the kidneys. Cysts may also be found in the liver, pancreas, spleen, ovaries, & large bowel.  Cysts in these organs usually do not lead to serious problems. PKD can also affect the brain and the heart.  If PKD affects the brain, it can cause an aneurysm which is a bulging blood vessel, this can burst, leading to a stroke or even death.  If PKD affects the heart, the valves can become floppy, resulting in a heart murmur for some people. 

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Pregnancy and PKD

The good news is that most women with PKD (80%) are able to have successful pregnancies. However, some women do have increased risk for serious complications for themselves and their baby. This is especially true for women who also:

• Have high blood pressure
• Have decreased kidney function

Women with PKD, especially those that already have high blood pressure, should be monitored closely throughout pregnancy  for a condition called preeclampsia (also called toxemia). Preeclampsia can be life threatening for both a mom and her baby. It can develop during pregnancy very suddenly, with little or no warning. This condition develops during pregnancy in healthy women with no prior symptoms, making it especially important for women with PKD and high blood pressure to receive early and ongoing prenatal care with a provider experienced with higher risk pregnancies.  

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Diagnosing PKD

There is no blood or urine test your healthcare can order to tell if you do or do not have PKD. Your family history is your first clue. Do either of your parents have kidney disease? What about your Grandparents? Do you have siblings that have been diagnosed with PKD? If you do have a family history you need to make an appointment with your healthcare provider to discuss your risk of having PKD and any tests that need to be done.  The best test that is also reliable and non-invasive is an ultrasound.  Ultrasound is an imaging test that can be used to get a good view of your kidneys. If you have developed cysts in your kidneys your provider will be able to see this in an ultrasound image.  Sometimes a CT Scan or MRI may also be used, and an MRI may be useful to measure and monitor the volume and growth of cysts and kidneys.  

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Treating PKD

Presently, there is no cure for PKD, however there is ongoing research with hopes to discover a cure and better treatments.   There is also ongoing research to understand the genetic basis of PKD, and how to slow the progression of kidney disease in PKD.  

Today there are supportive treatments to help to control symptoms, help to slow cyst growth, and to prevent or slow down the loss of kidney function in people with PKD, these include:

• Controlling blood pressure
• Treating bladder and kidney infections.  Seek treatment right away for suspected infection.
• Drink a lot of fluids each day after blood in urine first noted. 
• Medication to control pain.  Seek advice from your healthcare provider about which over the counter medications are safe to take if you have kidney disease.  
• Live a healthy lifestyle. This includes things like maintaining a healthy weight, exercising daily, eating a healthy diet that is lower in salt, sugar and limit over processed foods, Drink plenty of water and limit or give up beverages with caffeine, and stop any unhealthy habits, such as smoking. If you do smoke, make a contract with yourself and your family and start quitting today! 

In 2018 the FDA approved a new medication called tolvaptan for treatment of Autosomal Dominant Polycystic Kidney Disease (ADPKD).  This medication is used to help to slow the decline in kidney function in adults with this type of PKD.  Speak with your healthcare provider if you think this medication may be beneficial for you.

You are your best advocate when it comes to staying healthy, Don’t be afraid to speak up, ask questions, voice concerns, and seek out more information as it concerns your health conditions. Talk to your healthcare provider about your condition and know what to watch out for.  Follow the advice of your provider and communicate with them, they are there to help you to have the best health possible to live a fulfilling, happy, healthy life.

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References

National Kidney Foundation

PKD Foundation

John Hopkins Medicine

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About the Author

Monica McCarthy has bachelors in Political Science and Criminal Justice from Central Washington University.  A majority of her career was spent as a political consultant.   She currently works at KidneyLuv as a staff writer.

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Patient Education Disclaimer

This material is for informational purposes only. It does not replace the advice or counsel of a doctor or health care professional. KidneyLuv makes every effort to provide information that is accurate and timely, but makes no guarantee in this regard. You should consult with, and rely only on the advice of, your physician or health care professional.

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