You’re here because you or someone you know and care about has been diagnosed with a disease you have probably never heard of: Polycystic Kidney Disease or PKD. This section of the PKD Learning center covers information related questions and concerns people have when first diagnosed with PKD. Now is an exciting time in PKD research. Impressive advancements have been made recently to fight this disease, providing very real hope in the fight to end PKD.
Common Questions About How PKD Will Affect Your Health
Q What is PKD?
A Polycystic Kidney Disease affects an estimated 1 in 500 people, including newborns, children and adults regardless of sex, age, race or ethnic origin. It comes in two forms:
1. Autosomal dominant (ADPKD) is one of the most common life-threatening genetic diseases. ADPKD affects approximately 1 in 500. It does not skip a generation. There is usually a family history of ADPKD. Parents with ADPKD have a 50 percent chance of passing the disease on to each of their children.
2. Autosomal recessive (ARPKD) is a relatively rare genetic disorder, occurring in approximately 1 in 20,000 individuals. It affects boys and girls equally and often causes significant mortality in the first month of life.
A normal kidney is the size of a human fist and weighs about a third of a pound. However, with the presence of PKD, cysts develop in both kidneys. When many cysts develop, the kidneys can increase in both size and weight, sometimes weighing many pounds each. There may be just a few cysts or many, and the cysts may range in size from a pinhead to the size of a grapefruit.
Q: How does a person get PKD?
A: ADPKD: Because PKD is an inherited disorder, the dominant form of the disease (ADPKD) is passed from one generation to the next by an affected parent. An ADPKD parent has a 50% chance of passing the PKD mutation to each of his/her children at conception – having a child who inherits ADPKD with each pregnancy, no matter how many children a person has. In some families, all the children are affected; in other families, none are. Many families with multiple children will have affected and unaffected children. Although most individuals with ADPKD have a family history, scientists have also discovered that approximately 10-20 percent of the PKD patient community became affected through spontaneous mutation.
Two genes that cause ADPKD have been identified. About 85% of people with ADPKD have mutations in the PKD1 gene, located on chromosome 16. The remaining 15% of individuals have mutations in the PKD2 gene located on chromosome 4. There are no other PKD genes that have been identified to date.
The disease caused by ADPKD1 is more severe than that caused by ADPKD2. Individuals with mutations in the PKD1 gene develop cysts, hypertension and loss of kidney function at an earlier age compared to the ADPKD2 gene.
ARPKD: This recessive disease requires a mutated gene from each parent for the disease to manifest in a child, who has, then, 2 mutated genes. In most cases, there is no family history of the disease, and the parents do not have the disease themselves but are carriers.
Q: What are the symptoms of PKD?
A: Early in the disease, patients often experience no symptoms. In fact, many people don’t realize they have ADPKD because they have so few if any symptoms.
Symptoms of PKD:
High blood pressure, or hypertension, affects about 60% to 70% of men and 40% to 50% of women with ADPKD – in many cases the percentage tends to increase as GFR decreases. High blood pressure begins early during the course of ADPKD, often before there is abnormal kidney function. One theory for hypertension in ADPKD is that as cysts form and enlarge they press on blood vessels in the kidney, resulting in decreased blood flow. Sensors in the kidney tubule react as though the blood pressure in the kidney is low. A hormone called renin is then secreted, which in turn generates angiotensin II, constricting the blood vessels, and causing high blood pressure. If not treated, hypertension damages the kidneys, enlarges the heart and can cause strokes.
Chronic pain or heaviness is one of the most common problems for people with ADPKD. The pain is usually in the back or the sides and occasionally in the abdomen. The pain can be intermittent and mild requiring only occasional pain medicine such as Tylenol. In a small number of people, the pain can be constant and quite severe. The only non-steroidal anti-inflammatory over-the-counter pain medication recommended for use in ADPKD patients is Tylenol which is an analgesic. The other compounds may be further damaging to the kidneys.
Hematuria, or blood in the urine, is something that nearly 50% of those with ADPKD will experience. The urine may look pink, red or brown. Passing small amounts of red blood cells in the urine that can only be seen under a microscope may also occur. This is called microscopic hematuria. Blood in the urine can last for less than a day or go on for days. Strict bed rest, increased fluid intake, and acetaminophen (if there is pain) are usually the treatments if the bleeding is prolonged. Most of the time, bleeding is self-limited and resolves with these conservative measures.
Urinary tract infection (UTI) is caused by bacteria that have reached the bladder, kidneys or the cysts themselves. The infection usually starts in the bladder and can progress up the ureters into the kidneys. Although both men and women have UTIs, they are far more common in women. UTIs are common in the general population, but they appear to be more frequent in those with ADPKD. The most common symptom of UTI is pain or burning with urination and/or an urgent need to urinate even though there is only a small amount of urine. When the infection is in the kidney or in a cyst, there may be a sudden onset of fever, chills and back or flank pain.
Kidney stones occur in about 20%-30% of people with ADPKD, compared to 8%-10% in the general population. One reason kidney stones are more common may be due to cysts blocking the tubules, preventing normal drainage. When the urine stays in one area longer than it should, crystals can form and cause kidney stones. Another reason that stones may form in some people with ADPKD is that there is a decrease in urine citrate. Urine citrate is a substance that prevents formation of kidney stones. The symptoms of kidney stones are severe pain in the back, side or into the groin. Often there will be blood in the urine when passing a kidney stone.
Q: What are cysts?
A: A cyst in the kidney begins as an out-pouching of the nephron. Cysts can occur anywhere along the length of the nephron. Although polycystic means “many cysts”, only 2% of nephrons form cysts. The composition of the fluid inside the cysts often reflects the area in the nephron from which the cyst arose.
Approximately 70% of cysts detach from the nephron when they are still small, about 2 mm (1/8 inch) in diameter. Over time, the cysts enlarge and can become filled with clear fluid or fluid that contains blood or white blood cells.
Cysts can form in other organs, as well as the kidney; the most common extra renal site is the liver. Current research suggests that liver cysts form from cells lining the bile ducts or tubules of the liver rather than the liver cells themselves. It appears that rather than take the place of functioning liver cells, cysts merely push the liver cells aside. This is why liver cysts don’t cause liver failure even though the liver can become quite enlarged due to cysts.
Research has suggested that there are at least three components to cyst formation:
Cell proliferation: The cells of a cyst wall reproduce themselves more than normal kidney cells. This makes the cysts grow in size.
Fluid secretion: Secretion is a way of moving fluid across a cell. To form a cyst, there must be fluid. Secretion across the cyst wall into the cyst lumen; otherwise, there would merely be a ball of cells.
Abnormal basement membrane: The basement membrane is a very thin layer of tissue that the cyst cells sit on. In ADPKD this layer is thicker than usual. The basement membrane remodels as cysts grow. If this did not happen, cysts would not be able to enlarge.
In general, cysts cause problems because of their size and the space they occupy. The size of the kidneys and liver is directly related to how many and how big the cysts are. For example, people with kidneys over 15 cm (6 inches) are more likely to have pain and kidney dysfunction than people with smaller kidneys.
Q: What do the kidneys do?
A: The kidneys are bean-shaped and about the size of a fist, located in the middle of the back, below the rib cage. The kidneys filter approximately 200 quarts of blood daily, reabsorb 98% of the filtrate and regulate the composition of the blood by removing waste and by other compounds.
Other kidney functions include the production of three hormones:
Synthesis of Erythropoietin, a hormone which stimulates the production of red blood cells;
Synthesis of Renin which regulates blood pressure; and
Synthesis of Calcitriol, which is the active form of Vitamin D.
Q: What are complications of PKD?
A: ADPKD is not just a kidney disorder; other organs can be affected, including the liver, spleen, pancreas, vasculature, testes, seminal vesicles and intestines.
A large percentage of people with ADPKD will develop liver cysts during their lifetime. Liver cysts rarely occur in those under the age of 30 but do form and increase as a person ages. Even though there is an increase in liver size, the amount of functional liver tissue remains fairly constant. Liver cysts occur as often in men as in women. However, women have liver cysts at a younger age than men and usually have more aggressive liver disease. Women who have been pregnant are more likely to have liver cysts; and the cysts are more numerous and larger in women who have been pregnant compared to women who have not been pregnant.
Cardiovascular complications include high blood pressure, cerebral aneurysms and mitral valve prolapse (MVP), a condition where the valve separating the top and the bottom of the left side of the heart does not close properly. Sometimes this causes blood to leak back to the top part of the heart. This is called regurgitation and can be heard as a heart murmur. MVP occurs in approximately 26% of the people who have ADPKD compared to 2%-3% of the general population. Symptoms that can be associated with MVP are palpitations, a feeling that the heart is running away or that there are extra beats in the heart, and chest pain that is not associated with exercise or exertion.
People with ADPKD have about a 5%-10% risk of developing intracranial aneurysms; the percentage is higher if there is a family history of aneurysms. An aneurysm is an out-pouching in a blood vessel. Intracranial aneurysms occur in the blood vessels of the brain. Aneurysms can leak or rupture. The symptoms of a ruptured aneurysm can include sudden severe headache, pain in moving the neck, nausea and vomiting, and even loss of consciousness. All such symptoms require immediate medical attention. Patients with ADPKD and a family history of intracranial aneurysms have a higher incidence of developing an aneurysm (22%) and should be screened more frequently.
Gastrointestinal complications of ADPKD include diverticulosis Diverticula are out-pouchings of the large intestine (colon). It seems that people with ADPKD who are on dialysis or have had a transplant have diverticula more often and have more complications from diverticulitis, including infection (divertiulitis), than people who have other kidney diseases. In addition to liver cysts, cysts can also form in the pancreas.
Q: Am I at risk for other diseases because I have PKD?
A: ADPKD is not just a kidney disorder; other organs can also be affected.
We include some brief information about each of these conditions which can be associated with ADPKD. If you have ADPKD, you and your family should be aware of these possibilities so you can play a major role in your own care.
These can include, but are not limited to:
Over 80% of people with ADPKD have cysts in the liver during their lifetime. Liver cysts occur in those under the age of 30 but they are small and often detectable only by sensitive MRI scanning.
The liver can remain normal in size with few cysts or become enlarged. Even though there is an increase in liver size, the amount of functional liver tissue remains fairly constant. Therefore, rather than have cysts take the place of normal tissue as occurs in the kidney, cysts in the liver seem to push good tissue aside. This appears to be the reason that normal liver function is preserved even with many cysts and enlarged liver size.
Liver cysts occur more often in women than men; women have liver cysts at a younger age and more and larger cysts than men. Women who have been pregnant are more likely to have liver cysts; and the cysts are also more numerous and larger in women who have been pregnant compared to women who have not been pregnant. This suggests that female hormones may influence the development of liver cysts.
Mitral Valve Prolapse (MVP)
Mitral valve prolapse (MVP) is a condition where the valve separating the top and the bottom of the left side of the heart (left atrium and left ventricle) does not close properly. Sometimes this causes blood to leak back into the left ventricle. This is called regurgitation and can be heard during an examination of the heart as a heart murmur. Symptoms that can be associated with MVP are palpitations, a feeling that the heart is running away or that there are extra beats in the heart, and chest pain that is not associated with exercise or exertion. MVP occurs in approximately 26 percent of the people who have ADPKD compared to 2 – 3 percent of the general population. The majority of people with MVP never experience any major problems.
An aneurysm is an outpouching in a blood vessel, which can leak or rupture. In these events the symptoms can include sudden severe headache, pain in moving the neck, nausea and vomiting, difficulties with speech or movement, and even loss of consciousness. All such symptoms require immediate medical attention.
Recent studies done in the United States suggest that people with ADPKD have about a 5 – 10 percent risk of developing intracranial aneurysms. Intracranial aneurysms also seem to cluster in certain families – that is, if a member of your family has an aneurysm or has ruptured an aneurysm, you may be at a higher risk of having an aneurysm yourself.
Because the risk for aneurysm is small, not everyone with ADPKD needs to be tested. However, people who have ADPKD and a family history of aneurysm should be tested, along with those whose job or hobbies would put them or others at risk if they lost consciousness (such as those who fly airplanes or drive buses). It is important to inform your physician if you have a family history of intracranial aneurysms and/or if you have a high-risk occupation or hobby.
Both inguinal and umbilical hernias are more common in those with ADPKD. Inguinal hernias are outpouchings of the abdominal wall in the area of the groin and umbilical hernias are outpouchings of the abdominal wall at or near the navel. These should be surgically repaired if they are large or are causing other problems, just as they would be in someone who does not have ADPKD.
Diverticula are outpouchings of the large intestine (colon). It seems that people with ADPKD who are on dialysis or have had a transplant have diverticula more often and also have more complications from diverticula, including infection, than people who have other kidney diseases. At the present time, we are not recommending any routine evaluation for this possible symptom.
Q: How will PKD make me feel?
A: Early in the progression of the disease there are generally no symptoms at all. In fact, many people are never diagnosed with ADPKD because they either have no symptoms or a few symptoms that mimic other diseases. Often the first sign is high blood pressure, blood in the urine, or a feeling of heaviness or pain in the back, sides, or abdomen. Sometimes the first sign is a urinary tract infection and/or kidney stones.
Over time, as cysts grow, the kidneys will increase in size and weight. The additional size can cause the crowding of other organs, which can become uncomfortable and even painful. In some cases, the kidneys become so large that they cause the midsection to bulge. Men can look like they have a “beer belly” and women can appear pregnant.
Q: Can I prevent PKD?
A: Currently, no treatment can prevent cysts from forming or enlarging. Because PKD is a hereditary (genetic) disease, the only way to fully prevent it if you have a family history is to not have children. There is no intervention that will prevent the development of PKD in someone who inherits it.
Prenatal genetic testing is possible using samples from either chorionic villus sampling or amniocentesis. These genetic tests can either involve a direct search of the gene for mutations or an indirect association using linkage analysis. For linkage analysis, DNA samples are required from the fetus, the parents and other affected family members.
Another option for pre-natal diagnosis is a recently developed procedure called pre-implantation genetic diagnosis, or PGD. This is an early form of genetic diagnosis that involves the detection of specific genetic abnormalities in single cells taken from fertilized human embryos. The PGD procedure involves in vitro fertilization whereby eggs harvested from a mother are fertilized in a laboratory with the father’s sperm. Then, the fertilized embryos are tested for a specific genetic disorder (such as ARPKD) by removing one or two cells for genetic analysis. Embryos that are diagnosed as free of the disorder are then placed in the uterus with the intent to initiate a pregnancy.
Q: What can I do to slow or stop the progression of PKD?
A: There are several things patients can do to try to delay the onset of renal failure:
Control blood pressure. The current goal blood pressure for individuals with ADPKD is less than 130/80. The optimal choice of blood pressure medications remains uncertain but many in the nephrology field believe that ACE (Angiotensin Converting Enzyme inhibitor) or ARB (Angiotensin Receptor Blockers) are good medications to begin with.
Control cardiovascular risk factors by maintaining a healthy diet, maintaining healthy body weight, exercising regularly, avoiding smoking, etc.
As with any other kind of kidney disease, avoiding medications that could possibly injure the kidneys. PKD patients are advised to avoid all of the NSAID (Non Steroidal Anti Inflammatory Agents) – aspirin like agents, Advil, Aleve, Naproxin – except in rare circumstances and under a doctor’s supervision.
Q: How is PKD diagnosed?
A: A physician is alerted to the possibility of ADPKD in three different settings: when someone reports that there is a family history of ADPKD, when there are signs and symptoms that commonly occur in ADPKD, or when a test is done for some other reason and cysts are found in the kidney.
Currently, there are three main clinical tests that can be used to diagnose a person with PKD: ultrasound, computed tomography (CT) or magnetic resonance imaging (MRI).
Ultrasound is the most common and least costly screening method for ADPKD. A recent research study has produced diagnostic criteria that are useful for testing individuals having either the PKD1 or PKD2 mutation in the usual clinical setting in which molecular genotyping is seldom performed. To read a medical publication on this topic – which can also be printed and taken to your doctor – please click here.
Computed tomography (CT) and MRI scans are likely to be more sensitive than ultrasound but the sensitivity of these methods have not been systematically analyzed yet. CT scans, however, involve radiation and may also require iodinated contrast dye which can be toxic to the kidneys. CT scans or MRIs may be indicated for the evaluation of certain complications like bleeding into a cyst or a suspected kidney stone or alternatively if a more sensitive screening test with the ability to detect small cysts is deemed necessary.
DNA testing is available for ADPKD. There are two types of DNA tests: Gene linkage testing and Direct Mutation analysis. Gene linkage can determine ADPKD status with a 99 percent probability in informative families. Linkage testing is not a direct analysis of the DNA sequence of the PKD1 and PKD2 genes. Rather, it relies on the identification of certain “markers” in the DNA of several members of a family in which PKD has been diagnosed. For linkage analysis, blood samples must be obtained from the person being tested (the “proband”) as well as from several (typically three or more including the proband) persons from more than one generation of the proband’s family, including those affected and unaffected with ADPKD. A detailed family history and pedigree are also required. The results are typically reported to all family members that provided blood samples for the analysis.
In contrast, direct DNA sequencing requires only a single sample from the proband. This method is a direct analysis of the DNA sequences of the PKD1 and PKD2 genes. It is private, and the results are only reported to the proband’s physician and the patient (the proband). Using very sophisticated DNA sequencing apparatus, each of the nearly 17,000 “bases” of DNA are analyzed and the entire sequence is thus determined. This method is capable of identifying those changes in the sequence that are indicative of disease. It may be the only option if family members are unavailable or unwilling to participate in a linkage study. Each of these methods has pros and cons… you can check on the costs…
Additional Commonly Asked Questions
Q: Is there a relationship between PKD and cancer?
A: Although both cancer and PKD involve unregulated cell growth, there is no proven connection between the two diseases. Some of the drugs used to slow cell growth in cancer are being studied in animal models of cystic disease to see if they can slow or stop the progression.
Q: Is PKD contagious? How do other family members get it?
A: PKD is not contagious. It is a genetic disease meaning you have it in your chromosomes. Every person has 23 pairs of chromosomes, making a total of 46. Twenty-two pairs are called autosomes, and one pair is specifically devoted to determining the gender of an individual (X and Y chromosomes). Because the ADPKD genes are on autosomes, men and women have an equal chance of inheriting this disorder.
During reproduction, the chromosome pairs split in the formation of female eggs and male sperm. The woman donates 23 of her chromosomes to the baby and the man donates 23 in the sperm. In this way, when an egg is fertilized by a sperm, it will have the normal complement of chromosomes.
There are four possible ways the egg and the sperm of parents where one has ADPKD can combine. Two will contain the chromosome with the gene for ADPKD and two will not. Therefore, each child of a parent who has ADPKD has a 50 percent possibility of inheriting the affected chromosome.
Q: How do I tell my family I have PKD?
A: How you talk about PKD with your family is a very personal decision. Each individual will need to approach it slightly differently depending on the dynamics of their family.
Recommendations from several PKD experts suggest that you share the information with adult family members so they are educated about what is going on and can make informed choices about their own lives and issues related to their medical care.
With respect to children, discussions may be more complicated depending on the child’s age and their ability to handle and understand information about their own health of that of a family member with the disease.
Q: What’s the difference between PKD1 and PKD2 and how do I know which type I have?
A: There are two abnormal genes that cause ADPKD. About 80 – 85 percent of people affected with ADPKD have a mutation in the ADPKD1 gene located on chromosome 16, called PKD1. The rest of the ADPKD population has the mutation in the ADPKD gene located on chromosome 4 called PKD2. The ADPKD1 gene encodes the protein called polycystin-1 while ADPKD2 encodes polycystin-2. When these proteins function normally (not mutated), they are thought to play a role in kidney development and in the maintenance of normal renal structure (or “typical”, “standard” or “conventional”) development of kidney tissue.
It appears that the severity of the kidney disease caused by the ADPKD1 and ADPKD2 genes is slightly different. With the ADPKD1 gene, cyst development, the onset of high blood pressure, and loss of kidney function appear earlier as compared to the ADPKD2 gene, although there is a great deal of overlap.
A genetic test is the only way to tell which PKD gene an individual carries but we don’t usually test for this as it doesn’t affect clinical management.
Q: Should I have genetic testing done? Do my children need it?
A: This is a difficult question without a straightforward answer. There are treatable complications that are undetected in almost 60% of patients due to ADPKD. Complications include hypertension, urinary tract infections and hematuria or blood in the urine. These conditions contribute to disease progression in ADPKD. However, a diagnosis of an inherited kidney disease can limit access to life and health insurance coverage, and for those whose employment provides excellent health insurance coverage, a diagnosis can alter a decision regarding change of employment. These issues have tremendous impact with regard to undergoing screening for a diagnosis of ADPKD.
An alternative to undergoing screening for a diagnosis of ADPKD is that at-risk individuals can practice “universal precautions”, i.e., assume that everyone at risk has ADPKD and treat accordingly. This would include having a home blood pressure measuring device, having a physician obtain blood pressure measurements and check urinalyses regularly, and having blood work done to measure kidney function. Should symptoms develop, such as flank pain, back pain, pain with urination, or blood in the urine, referral to a nephrologist is recommended. Importantly, the field of scientific investigation in ADPKD is making tremendous progress, and, at the current pace we are rapidly developing an increased understanding of the PKD genes and their protein products. This will hopefully spur development of specific therapies for ADPKD. Those diagnosed early with ADPKD would benefit the most from such therapies. All of these issues make this decision a case-by-case and year-by-year consideration. It is worthwhile to discuss all questions and concerns with your health care provider before proceeding with a screening test for the presence of ADPKD.
Q: Where can I get tested to find out if I have PKD?
A: Click here for a list of genetic test sites around the world.
Q: Should I seek a diagnosis?
A: The question of whether or not to be tested or to have your children tested for PKD before symptoms appear is a difficult and personal one. Once a diagnosis is confirmed by imaging or genetic testing, it becomes part of an individual’s health records. Click here to learn more about what a diagnosis means for you.
What is PKD?
Ronald D Perrone, MD – Professor of Medicine at Tufts Medical center explains Polycystic Kidney Disease (PKD).
Basics of PKD Webinar
Nearly 1,000 people from around the world took part in our first educational webinar. Dr. Ron Perrone of Tufts University Medical center guided participants through a wide range of PKD topics. The one hour webinar covered the basics of PKD, but also touched on a few deeper issues during the Q &A session.