Polycystic Kidney Disease
What is polycystic kidney disease?
Normal kidneys are about the size of a closed fist. Polycystic kidneys have cysts that form in the kidneys. These cysts are filled with fluid and, depending on their size and how many there are, will change the size of the kidneys. There are medical journals showing pictures of polycystic kidneys that are about the size of a football and weigh over 20 pounds.
In addition to changing the size of the kidney, the cysts can interfere with healthy kidney functions and after time lead to kidney failure. About half of the people diagnosed with polycystic kidney disease will experience end stage renal disease (ESRD) and will need dialysis or a kidney transplant.
PKD is most commonly believed to equally affect men and women of all races. However, some studies have shown that the disease may occur more often in white people than in African Americans and in females more often than males.
PKD is the number four cause of kidney failure in Americans, and an estimated 600,000 people in the U.S. currently have it.
How does someone get polycystic kidney disease?
You cannot catch PKD from a virus or by being exposed to another person who has it. Polycystic kidney disease is hereditary and there are two forms of the disease that are passed down from a parent:
- Autosomal dominant polycystic kidney disease (ADPKD) is by far the most common form of PKD and runs in families. It is passed from parent to child. The odds are 50/50 of a child inheriting it from an affected mother or father. About 10% of people with ADPKD have not inherited the disease from a parent, but have a gene that mutated causing the disease.
- Autosomal recessive polycystic kidney disease (ARPKD) is rare and strikes infants, sometimes even before birth. It is also known as “infantile PKD.” Both parents must be “carriers” of the ARPKD gene to pass it to a child and each of their children has a one in four chance of getting the disease.
Autosomal dominant polycystic kidney disease (ADPKD)
Autosomal dominant makes up 90 percent of all cases of PKD. It is the most frequently inherited disease. It is called “dominant” because to get the disease a person has to receive one copy of a dominant gene from a parent. Those with ADPKD will usually have no symptoms until they reach between 30- and 40-years old.
When ADPKD is first diagnosed it is usually because a doctor is aware of a family history and is looking for the condition, there are symptoms or a medical test taken for another reason brings the kidney disease to light.
Because ADPKD runs in families, a person will want to tell their doctor about their family history with the disease. Even though other family members may have ADPKD, the symptoms and affects of the disease are not usually similar. Each family member may have a different experience with ADPKD. Some may have severe symptoms, while others may not have any at all.
The most common symptoms are high blood pressure, blood in the urine and/or pain in the back, sides and belly.
Between 60 and 70 percent of patients with ADPKD have high blood pressure. Most likely this is due to the increased pressure the enlarged cysts place on blood vessels in the kidneys. Medicine, diet, exercise and lifestyle changes can help reduce and control blood pressure, as well as slow the progress of ADPKD. A doctor will tell patients with PKD what they can do to help maintain kidney health for as long as possible.
At some point almost half of those with ADPKD may find blood in their urine (hematuria). When urine appears pink, red or brown this is a sign blood is present. This can happen for a day or more, but usually less than a few days. Usually the patient will be told to rest in bed and drink a lot of water. If there is pain, acetaminophen (Tylenol®) is usually recommended. If blood is still present after a couple days, a hospital stay may be necessary.
Pain is common for people with ADPKD. The pain generally occurs when the kidneys get very large from the cysts. For some people the pain is constant, for others it comes and goes. The pain can vary from mild to unbearable. Pain is usually where the kidneys are located, in the back and sides. Tylenol® can provide some relief. If pain is severe, surgery can make the cysts smaller, which may help, but it is temporary and not a cure.
Other possible complications from ADPKD
Urinary tract infections are more common in people with ADPKD and should be treated with antibiotics as soon as possible to keep the infection from spreading into the cysts around the kidneys. Antibiotics do not penetrate cysts, so these infections need to be treated right away.
When cysts block the drainage of the kidneys, kidney stones can develop—in 20 to 30 percent of patients. This is double the rate of people without PKD. When kidney stones are being passed it is usually very painful and blood is visible in the urine.
Up to 70 percent of those with ADPKD may also develop liver cysts as they get older. Cysts may enlarge the liver, but liver function is not affected. As many men as women develop liver cysts, although women develop them at a younger age and women who have been pregnant develop them with more often. Women also have more numerous and larger cysts.
The heart can also be affected by PKD. Mitral valve prolapse (MVP) occurs in the hearts of 26 percent of those with ADPKD as compared to two to three percent of the general population. MVP can cause palpitations, chest pain and a feeling of extra or faster beats in the heart because the valve does not close as it should.
Headaches may be caused by high blood pressure or by enlarged blood vessels (aneurysm) in the brain. For this reason, people with ADPKD should see a doctor about headaches, especially before taking over-the-counter pain medication. The doctor may recommend getting checked regularly for aneurysms if there is a family history of ruptured brain aneurysms, which is a complication of ADPKD.
Medical tests to detect PKD
Many people with autosomal dominant polycystic kidney disease have no signs or symptoms of the disease. Some people can live their entire life not knowing they have polycystic kidney disease. In these cases routine checkups including blood and urine tests may not even show any signs of PKD.
Ultrasound is most commonly used to detect initial-stage ADPKD. Sound waves pass harmlessly through the kidneys and create a picture for the doctor to examine. The doctor will be able to see the cysts if they are large enough.
Computed tomography (CT) scans and magnetic resonance imaging (MRI) are also used to make diagnosis. CT uses radiation (an x-ray) and often requires injecting a dye for better viewing.
Autosomal recessive polycystic kidney disease (ARPKD)
Autosomal recessive PKD is also hereditary, but comes from a different gene than causes the autosomal dominant form of PKD. ARPKD is called “recessive” because two copies must be passed on, one from each parent. Both parents must have the gene for ARPKD to pass the disease to their child, even if they don’t have PKD. If both parents are carriers of the abnormal gene, the chance of their child getting ARPKD is one in four. If only one parent has the gene, their baby cannot get the disease.
ARPKD affects about one out of every 10,000 people in the US.
Unlike ADPKD, which doesn’t show symptoms until middle age, ARPKD is usually diagnosed very early on. An ultrasound can reveal cysts in a fetus’s kidneys, while it is still in the womb. Ultrasound imaging has no side effects and is safe for all patients, including pregnant women and fetuses.
Because this disease can start affecting babies before they are born, it is also called “infantile PKD.” Babies with this disease have a high death rate in their first month. Survival time depends on how bad a case of ARPKD a baby has. About 50 percent of babies with ARPKD will die at birth or minutes after because the overly enlarged kidneys interfere with breathing. Some infants die within days or months, while other children have normal kidney function for a few years. There are even people with ARPKD who can live into their adult years. The disease, however, affects other areas of the body including the liver, spleen and pancreas leading to low blood cell counts, varicose veins and hemorrhoids.
Children with ARPKD also have a liver problem called congenital hepatic fibrosis. Blood flow from the veins in the liver can be blocked due to scarring that can lead to an enlarged liver.
Blood pressure must also be monitored. Most children develop high blood pressure by the time they are a year old. Frequent urination and urinary tract infections are other complications of ARPKD. The body size of children with ARPKD may be smaller than average because the kidneys are not able to provide the bones with the nutrients necessary for growth.
To help children with ARPKD be as healthy as possible they should see a pediatric nephrologist (a doctor specializing in caring for children with kidney disease). The pediatric nephrologist will prescribe medicine to control high blood pressure and antibiotics for urinary tract infections when necessary. The doctor will monitor the liver, kidneys and the growth of the child. Sometimes, if growth is poor, growth hormones may be prescribed.
By age 60 about half of the people with ADPKD will need dialysis or a transplant to replace the function of their kidneys. Of children with ARPKD, about one-third will need dialysis or kidney transplant by the time they are 10-years old.
When the kidneys are no longer able to remove waste from the blood, toxins build up causing symptoms such as:
- Not feeling well
- Lack of energy
- Difficulty breathing
- Weight loss
- Difficulty concentrating
A kidney transplant will provide a new kidney that will take the place of the ones that no longer work. Anti-rejection medicines will need to be taken so the body will accept the new kidney.
The future of PKD Research
In 2000, scientists found that a drug used to treat cancer also inhibited cyst formation in mice with the PKD gene. And in 2003, another compound inhibited cyst formation in mice with the ADPKD and ARPKD genes. By identifying the processes that trigger the formation of kidney cysts, and experimenting with drugs that can inhibit or block them, there is hope that research will lead to improvements in treating PKD and a cure.
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