Polycystic Kidney Disease
Polycystic kidney disease is a condition where many cysts develop in the kidneys. A cyst is a fluid-filled sac. 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 either one or both genes for this disease is faulty, which results in the formation of cysts in the kidneys. Men and women are equally affected. 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.
- 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. Two faulty genes are present in this condition, inherited from each parent (who will be well but will be ‘carriers’ of the faulty gene).
- 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.
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.
The affected kidneys get bigger. Sometimes they become as big as three to four times the normal size and can be felt on examination.
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?
Symptoms develop most 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
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. 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 the kidneys are damaged. As a result, the 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. (refer to CKD on pageXX)
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. 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.
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.
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.
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 blood pressure and kidney function are fine, some general points to note are:
- An ultrasound scan of the kidneys, a blood pressure check, and blood tests to monitor your kidney function are advised at least once a year.
- Contact sports where one might get a bash to the abdomen or sides of the back should be avoided. The enlarged kidneys are more prone to be damaged or even ruptured by injuries that would not normally cause damage to kidneys.
- Anti-inflammatory painkillers should not be taken unless under the direction of a doctor as these can make kidney function worse in some people. Some other drugs may also affect the kidneys. Therefore, a doctor should always be told of ADPKD if prescribing drugs for any condition.
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.
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 (See page XX)
If end-stage kidney failure develops, kidney dialysis or a kidney transplant is required to survive.
If persistent pain develops from the enlarged kidneys then painkillers may be needed. 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.
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 one is diagnosed with ADPKD, then that patient’s brothers and sisters may also have PKD . If the patient has any children, they can also be tested to see if they have the disease before it causes symptoms. The main reasons to know that one has the disease before any symptoms develop are:
- To 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.
- As a ADPKD patient has an increased risk of developing cardiovascular disease, lifestyle changes can be made to address 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.