Polycystic kidney disease causes many cysts (fluid-filled sacs) to develop in the kidneys. The most common type is an inherited condition called autosomal dominant polycystic kidney disease (ADPKD). With ADPKD, problems commonly do not develop until the age of 30-50, with some people never developing any problems. The two common problems that develop are high blood pressure and kidney failure. About half of people with ADPKD develop kidney failure requiring dialysis or a kidney transplant by the age of 60.
Understanding kidneys and urine
The kidneys clear waste materials from the body and maintain a normal balance of fluids and chemicals in the body. The two kidneys lie to the sides of the upper abdomen, behind the intestines, and either side of the spine. Each kidney is about the size of a large orange, but bean-shaped.
A large renal artery takes blood to each kidney. The artery divides into many tiny blood vessels (capillaries) throughout the kidney. In the outer part of the kidneys tiny blood vessels cluster together to form structures called glomeruli.
Each glomerulus is like a filter. The structure of the glomerulus allows waste products and some water and salt to pass from the blood into a tiny channel called a tubule, while keeping blood cells and protein in the bloodstream. Each glomerulus and tubule is called a nephron. There are about one million nephrons in each kidney.
As the waste products, water and salts pass along the tubule there is a complex adjustment of the content. For example, some water and salts may be absorbed back into the bloodstream, depending on the current level of water and salt in your blood. Tiny blood vessels next to each tubule enable this fine adjustment of the transfer of water and salts between the tubules and the blood.
The liquid that remains at the end of each tubule is called urine. This drains into larger channels (ducts) which drain into the renal pelvis (the inner part of the kidney). From the renal pelvis the urine passes down a tube called a ureter which goes from each kidney to the bladder. Urine is stored in the bladder until it is passed out through the urethra when we go to the toilet.
The cleaned (filtered) blood from each kidney collects into a large renal vein which takes the blood back towards the heart.
What is polycystic kidney disease?
- A cyst is a fluid-filled sac. Cysts occur in various sizes, in various conditions, and in various parts of the body.
- Polycystic means many cysts.
- Polycystic kidney disease is a condition where many cysts develop in the kidneys. The cysts are benign (non-cancerous) and develop from some of the kidney tubules.
Note: it is common for healthy people, especially older people, to develop, one, two, or even a few harmless cysts in a kidney. These usually cause no problems and are not due to polycystic kidney disease.
Polycystic kidney disease is a genetic condition. This means that one or more of your genes is faulty, which results in you making many cysts in your kidneys. There are different types of polycystic kidney disease:
- Autosomal dominant polycystic kidney disease (ADPKD). This is the most common type. This is a hereditary condition caused by a faulty gene which is inherited from one parent. If symptoms and problems develop, they usually start in adulthood. See the rest of this leaflet for details.
- Autosomal recessive polycystic kidney disease (ARPKD). This is a rare condition which affects about 1 in 20,000 people. Problems typically develop soon after birth. You need two faulty genes to develop this condition. You get one faulty gene from each parent (who will be well but will be 'carriers' of one faulty gene each).
- Non-hereditary polycystic kidney disease. In about 1 in 10 people who develop polycystic kidney disease, the faulty gene is a new mutation in the affected person. So, there are no other family members affected.
Who gets autosomal dominant polycystic kidney disease?
ADPKD affects about 1 in 800 people in the UK. Men and women are equally affected. It is a hereditary condition with an autosomal dominant pattern of inheritance. Briefly, this means that you have a gene that is faulty and each child that you have has a 50:50 chance of inheriting the faulty gene and also developing the condition. The faulty gene of ADPKD causes a problem in the membrane (wall) of cells in certain parts of the body, in particular certain kidney cells. The fault in the cells leads to the development of cysts.
In fact, with ADPKD, two faulty genes have been identified that can cause the condition. Therefore, ADPKD is divided into two subtypes - ADPKD I (about 17 in 20 cases), ADPKD 2 (about 3 in 20 cases). These are two distinct genetic disorders, but result in the same problem of causing polycystic kidneys. However, as a general rule, the severity of the condition tends to be worse with ADPKD I compared with ADPKD 2. There is possibly a third faulty gene that accounts for a small number of cases - but this is uncertain.
How does autosomal dominant polycystic kidney disease progress?
The disease develops very slowly and therefore symptoms and problems usually do not develop until adulthood. More and more cysts, sometimes up to several hundred, develop over the years. The size of most of the cysts ranges from the size of a pinhead to 2 cm in diameter. However, some can become much larger. The cysts press on the normal parts of the kidney and gradually replace much of the normal kidney tissue. In time, this affects the function of the kidney, as less and less normal kidney tissue is able to filter the blood. In many cases, the function of the kidneys eventually becomes so bad that end-stage kidney failure develops (see below).
The affected kidneys get bigger. Sometimes they become as big as three to four times the normal size and can be felt when a doctor examines your abdomen.
However, the extent of cyst formation and kidney damage can vary greatly from person to person. About one in three people with ADPKD get to the age of 70 without any serious kidney failure.
What are the initial symptoms of autosomal dominant polycystic kidney disease?
It is quite common to have ADPKD for years without developing any symptoms or realising that you have the condition. Indeed, some people with ADPKD never develop any symptoms or problems. However, in most cases, symptoms develop at some point - commonly sometime between the ages of 30 and 50 years. Some of the first symptoms and signs that may develop include one or more of the following:
- Blood in the urine - which may come and go. This is due to one or more cysts bleeding from time to time.
- Protein in the urine.
- Pain over one or both kidneys. This is due to the enlarged kidneys.
- Kidney stones. These occur in about 1 in 5 people with ADPKD. Symptoms of a kidney stone can range from no symptoms at all to severe pain if a stone becomes blocked in a ureter.
- Abdominal pain and/or a swollen abdomen.
- High blood pressure.
- Recurring kidney infections.
These symptoms may alert a doctor to investigate further and ADPKD may then be diagnosed. In some cases, the diagnosis is only first made when a complication develops such as kidney failure (see below).
How is autosomal dominant polycystic kidney disease diagnosed?
Tests that may be done if ADPKD is suspected include the following:
- Ultrasound scan of the kidneys. This is a safe and painless test that uses sound waves to create images of organs and structures inside your body. ADPKD in an adult can usually be confidently diagnosed with this test.
- CT or MRI scans are more detailed scans and may be done if there is any doubt about the diagnosis.
- Urine tests to check for blood and protein in the urine.
- Blood tests to check on the function of the kidneys.
Some cases are diagnosed before any symptoms develop, due to screening family members of affected people, or by chance if a kidney scan is done for another reason.
What are the possible complications of autosomal dominant polycystic kidney disease?
Possible complications include the following:
Decline in kidney function (failing kidneys)
The medical term for reduced kidney function is chronic kidney disease (CKD). CKD means that your kidneys are damaged. As a result, your kidneys may not work as well as they should to clear waste materials from the body and to maintain a normal balance of fluids and chemicals in the body. Various conditions can cause CKD, including ADPKD.
A blood test called the estimated glomerular filtration rate (eGFR) is used to diagnose CKD. If your kidneys are not working properly the eGFR is below the normal value. CKD is divided into five stages depending on the eGFR level - stage 1 (very mild) to stage 5 (end-stage kidney failure). The eGFR is repeated from time to time to monitor the progression of CKD.
Most people with mild-to-moderate CKD (stage 1 to 3) do not have any kidney failure symptoms. Symptoms tend to develop when CKD becomes severe (stage 4) or worse. The symptoms can include: feeling tired; a poor appetite; weight loss; itchy skin; muscle cramps; swollen feet; puffiness around the eyes; being pale due to anaemia; feeling sick. As the kidney function declines from stage 4 to 5, you are likely to feel more unwell. End-stage renal failure (stage 5) is eventually fatal unless treated with dialysis or a kidney transplant.
About half of people with ADPKD have developed stage 5 CKD (end-stage renal failure) by the age of 60, with about 6 in 10 developing it by age 70. It most commonly develops between the ages of 40 and 60.
High blood pressure
The kidneys play a vital role in controlling blood pressure. Having ADPKD greatly increases the chance that high blood pressure will develop. About half of people with ADPKD aged 20-34 years have high blood pressure, and most people with ADPKD will develop high blood pressure at some point in their life. High blood pressure in itself does not usually cause symptoms. So, it is easy to be unaware that you have high blood pressure. However, untreated high blood pressure can cause further damage to the kidneys, and greatly increases the risk of developing heart disease and stroke. Therefore, early detection and treatment of high blood pressure are important.
Cysts in other parts of the body
Although the kidneys are the main site affected, cysts may also develop in other parts of the body. For example, cysts commonly develop in the liver. Typically, cysts in the liver do not cause any symptoms or problems. The cysts do not usually affect the function of the liver and so do not cause liver failure. However, in some cases they grow quite large and sometimes cause pain or other problems from pressure effects. If problems do develop from liver cysts, they tend to occur later in life - in middle or old age. An ultrasound scan which diagnoses cysts in kidneys will also usually detect liver cysts.
Some other parts of the body may also develop cysts, such as the pancreas, seminal vesicles (the small glands that make semen in men), and the arachnoid membrane (tissue next to the brain). However, even if these develop, they rarely cause any problems.
Aneurysm of an artery in the brain
An aneurysm is a localised swelling of a blood vessel. Up to 1 in 10 people with ADPKD develop an aneurysm in a brain artery. In most cases this does not cause symptoms or problems. However, there is a risk that an aneurysm may rupture (burst) to cause a bleed next to the brain (subarachnoid haemorrhage). This is uncommon, but serious if it occurs. Some doctors advise that people with ADPKD who have a family history of aneurysm should have a routine brain scan. Abnormalities in other blood vessels occasionally occur.
Heart valve abnormalities
About 1 in 5 people with ADPKD develop mitral valve prolapse. This causes the mitral valve in the heart to become a bit leaky. However, this does not usually cause any serious problems. See separate leaflet called Mitral Regurgitation for details.
Some people with ADPKD develop chronic (persistent) pain over their enlarged kidneys.
Women with ADPKD who become pregnant have an increased chance of developing a complication of pregnancy, called pre-eclampsia. However, most women with ADPKD who become pregnant have a normal uneventful pregnancy.
There may be a slight increase in the risk of developing diverticulae (pouches) in the colon. However, in most cases this does not cause any problems. See separate leaflet called Diverticula for details.
What is the treatment for autosomal dominant polycystic kidney disease?
Many people with ADPKD remain well and free of problems for years after the condition is diagnosed. No particular treatment may be needed for a time. However, even if your blood pressure and kidney function are fine, some general points to note are:
- Once a year you will normally be advised to have an ultrasound scan of the kidneys, a blood pressure check, and blood tests to monitor your kidney function.
- It is best to avoid contact sports where you may get a bash to the abdomen or sides of the back. The enlarged kidneys are more prone to be damaged or even ruptured by injuries that would not normally cause damage to kidneys. For example, a hard rugby tackle.
- Do not take anti-inflammatory painkillers such as ibuprofen, indometacin, etc, unless under the direction of your doctor. These can make kidney function worse in some people. Some other drugs may also affect the kidneys. Therefore, tell a doctor or pharmacist that you have ADPKD when you are prescribed or buy any medication.
There is no treatment that can reverse or affect the growth of the cysts although this area is under research. Treatment is aimed at controlling symptoms and complications as much as possible if and when they occur. This may include one or more of the following:
Treating high blood pressure
Good control of blood pressure can slow down the progression of kidney damage and so the progression of CKD. See separate leaflet called High Blood Pressure (Hypertension) for details.
Managing chronic kidney disease
People with CKD due to any cause (including ADPKD) have an increased risk of developing cardiovascular diseases such as heart disease and stroke. This is why reducing any other cardiovascular risk factors is so important. Briefly, this typically includes:
- Good control of blood pressure (and blood glucose level if you have diabetes).
- Medication to lower the cholesterol level - needed in many cases.
- Where relevant, to tackle lifestyle risk factors. This means to:
If CKD becomes severe (stage 4-5) you may need treatment to combat various problems and symptoms caused by the poor kidney function. If end-stage kidney failure develops (stage 5), you are likely to need kidney dialysis or a kidney transplant to survive. Also, people with stage 3 CKD or worse should be immunised against influenza each year and have a one-off immunisation against pneumococcus. People with stage 4 CKD should be immunised against hepatitis B.
See separate leaflet called Chronic Kidney Diseasefor details.
If you develop persistent pain from the enlarged kidneys then you may need painkillers. Sometimes an operation to drain or remove some particularly large cysts may be done if they are thought to be causing pressure and pain. Other pain-relieving techniques are sometimes needed.
Treating other cysts
If other cysts develop in other parts of the body and cause symptoms and problems, then various other treatments may be needed. For example, if a liver cyst causes problems, sometimes it is possible to drain or remove it.
Urine and kidney infections
It is best to promptly treat any urine or kidney infection that may develop. Sometimes a cyst becomes infected which may need long-term antibiotic treatment, or other treatments.
Should family members be screened (tested) for autosomal dominant polycystic kidney disease?
If you have ADPKD you may wish to tell your brothers and sisters that they have a chance of also having it. If you have any children, you may also want them to be tested to see if they have the disease before it causes symptoms. The main reasons to know that you have the disease before any symptoms develop are:
- So that you can have regular blood pressure checks to detect and treat high blood pressure as early as possible. This can make a difference to the long-term outlook.
- To know that if you do have ADPKD you have an increased risk of developing cardiovascular disease. Therefore, you may wish to make even greater efforts whilst younger to address any lifestyle issues such as smoking, exercise, obesity, etc.
- To make informed decisions about parenthood.
- Simply, to be aware of the problems that may occur in the future.
However, having the diagnosis 'hang over you' before it causes any symptoms or problems can cause anxiety in some people. So, screening is not without potential harm. Genetic counselling may be appropriate in some cases.
An ultrasound scan can usually detect ADPKD before it causes any symptoms. Until recently, screening by using an ultrasound scan was offered to family members at about the age of 20. However, some doctors recommend ultrasound scans every five years from late childhood until the age of 30. At this age, a clear scan virtually rules out the diagnosis of ADPKD.
A specialised genetic blood test is sometimes used to screen for ADPKD in younger people before cysts are detectable by ultrasound scan. For example, this may be done in a younger relative of someone with ADPKD who has volunteered to be a kidney donor. The test can rule out that they have ADPKD and are therefore suitable to be a donor.
Further help & information
Further reading & references
- Diagnosis and management of chronic kidney disease, Scottish Intercollegiate Guidelines Network - SIGN (June 2008)
- Chronic kidney disease, NICE Clinical Guideline (September 2008)
- Torres VE, Harris PC, Pirson Y; Autosomal dominant polycystic kidney disease. Lancet. 2007 Apr 14;369(9569):1287-301.
- Torra R, Polycystic Kidney Disease, Medscape, Oct 2011
|Original Author: Dr Tim Kenny||Current Version: Dr Gurvinder Rull||Peer Reviewer: Dr Adrian Bonsall|
|Last Checked: 05/11/2012||Document ID: 7225 Version: 5||© EMIS|
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.