Polycystic Kidney Disease
What is polycystic kidney disease?
Polycystic kidney disease (PKD) is a predominantly inherited disorder that causes many cysts of varying size to develop in the kidneys. The cysts are fluid-filled and noncancerous. However, as they grow, they can enlarge the kidneys and change their shape. Very large or numerous cysts eventually interfere with the kidney’s ability to function and filter and clean the blood. Cysts can also develop in other organs, most commonly the liver.
About 600,000 Americans live with PKD. It affects people of both sexes and all races equally. However, genes play a major role in the risk of PKD. In most cases, PKD runs in families, with parents passing abnormal genes to their children. There are two forms of PKD:
- Autosomal dominant: The disease can pass from parent to child if only one parent as an abnormal gene. Each child has a 50% chance of getting PKD. This is the most common form of PKD, accounting for 90% of cases. Most often, it doesn’t show up until adulthood, between ages 30 and 40.
- Autosomal recessive: Both parents must have an abnormal gene to pass along this form of PKD. Each child has a 25% chance of getting PKD. It is much rarer than the autosomal dominant form. Doctors often diagnose this form shortly after birth, but it may not show up until later.
The PKD gene mutation can also appear spontaneously. This means there is no familial link and neither parent has the abnormal gene. This form is very rare.
With the main form of PKD, it is very common for people to not know they have the disease for a long time. It may show on imaging exams for other reasons. Or symptoms may eventually develop. Symptoms include back pain, headaches, frequent urinary tract infections, or kidney stones. Laboratory tests may show blood in the urine or altered kidney function.
At this time, there is no cure for PKD. Treatment aims to slow the decline in kidney function and prevent and delay complications. Treatment involves lifestyle changes and controlling other conditions that affect the kidneys, such as high blood pressure. There is also a drug that may help preserve kidney function in some people with PKD.
Progressive kidney failure is the main complication of PKD. PKD can also affect other organs. In some organs, such as the pancreas and spleen, the cysts do not cause serious problems. However, in the brain, PKD can cause aneurysms. In the heart, it can cause valve disease.
What are the symptoms of polycystic kidney disease?
Most of the time, cysts are 0.5 inches or larger before they cause symptoms. It is common not to notice symptoms until well into adulthood. People with the disease may be 30 or 40 years old or even older before symptoms appear.
Common PKD symptoms include:
- Abdominal fullness or bloating
- Back or side pain, which can become chronic
- Frequent urinary tract infections
People with PKD may also have high blood pressure. Traces of blood in the urine, along with other markers of declining kidney function, can show up on laboratory tests. However, the signs and symptoms of PKD are similar to several conditions that can affect the kidneys. Imaging exams are necessary to see the cysts and diagnose PKD.
What are the risk factors for polycystic kidney disease?
PKD is a genetic disorder, meaning it runs in families. Genetic inheritance can be challenging, but it’s important to understand for PKD. People have two copies of each gene, A and B. They pass one copy of each of their genes to their children. So, children inherit one copy from parent 1 and one from parent 2. For each child, there are four possible combinations of genetic inheritance: A1A2, A1B2, B1A2 and B1B2.
PKD1 and PKD2 cause the autosomal dominant form of the disease. In this inheritance pattern, only one parent needs to have a copy of the abnormal gene to pass the disease to a child. If A1 is the abnormal gene, there is a 50% chance of getting the disease for each child.
PKHD1 causes the autosomal recessive form. Here, both parents must have an abnormal copy of the gene. It is necessary to inherit two copies of the abnormal gene, one from each parent, in order to pass the disease to a child. Inheriting only one copy of the genetic mutation from one parent will not cause disease. In this scenario, both A1 and A2 are abnormal and each child has a 25% chance of getting the disease.
How can you reduce the risk of polycystic kidney disease?
At this time, it is not possible to prevent PKD. People with a parent, sibling or child who has PKD should talk with their doctor about screening tests. Finding out about PKD early allows you to take steps to protect your kidneys.
If you have PKD and are concerned about passing the disease to your children, consider working with a genetic counselor. These healthcare providers are best able to help you understand the risk to your children and work through these complicated decisions.
How is polycystic kidney disease treated?
The goal of polycystic disease treatment is to slow cyst growth and kidney damage. This may be accomplished with the following:
- Avoiding caffeine or at least limiting it to 2 to 3 cups of coffee per day
- Controlling high blood pressure, especially with angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs), which can help protect the kidneys
- Drinking plenty of water
- Leading a healthy lifestyle by getting regular exercise, getting a full night’s sleep every night, maintaining a healthy weight, and quitting smoking
- Promptly treating urinary tract and kidney infections
There is no specific polycystic kidney disease diet. Nor is there solid evidence that changing your diet will stop or slow the growth of cysts. However, a healthy diet is important for anyone with a chronic disease. So, it’s wise to consult a dietitian if you have PKD. As kidney function declines, diet becomes more important. Your doctor may recommend specific changes, such as limiting protein or potassium.
Treatment can also involve medicine to control symptoms, such as pain
In 2018, the U.S. Food and Drug Administration approved the drug, tolvaptan (Jynarque), for the treatment of autosomal dominant PKD. The drug can help slow cyst growth and preserve kidney function. This may delay the need for dialysis or kidney transplantation for years. However, the drug is hard for some people to tolerate. And it carries a risk of liver injury, which requires people to participate in a special program to monitor liver function. The drug is also very expensive. Talk with your doctor to find out if it is a reasonable option for you.
What are the potential complications of polycystic kidney disease?
With PKD, progressive kidney function decline is the main complication. However, not everyone with PKD will end up with kidney failure. Only 50% of people with PKD will develop kidney failure by age 60. By age 70, about 60% will develop it. Regular kidney function monitoring can alert your doctor to declines that require attention.
PKD can also cause cysts and problems with other organs, including the liver, pancreas, spleen and ovaries. In these organs, it usually doesn’t cause serious problems. People with PKD are also more likely to develop groin and umbilical hernias.
PKD can cause significant complications in other organs including:
- Brain: PKD can cause brain aneurysms. These are weakened, bulging areas in an artery wall that have the potential to rupture. This can cause stroke and life-threatening bleeding in the brain.
- Colon: PKD can cause diverticulosis, which are weakened pouches in the large intestine. These small bulges can become inflamed or even rupture, causing a life-threatening infection.