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.
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.
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:
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.
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.
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:
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).
Tests that may be done if ADPKD is suspected include the following:
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.
Possible complications include the following:
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.
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.
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.
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.
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.
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:
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:
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.
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:
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.
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.
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.
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:
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.