Autosomal Dominant Polycystic

Kidney Disease (ADPKD)

This page is a shortened version of a booklet on ADPKD prepared by the Institute of Nephrology, Institute of Medical Genetics and Department of Paediatric Nephrology, University of Wales College of Medicine, Cardiff, Wales. Please ask your consultant if you would like one.

What is Autosomal Dominant Polycystic Kidney Disease?

Autosomal dominant polycystic kidney disease (abbreviated as ADPKD) is an inherited disease in which cysts develop in both kidneys. In a proportion of people this condition will cause kidney failure in adult life.

What are Cysts?

A cyst is a cavity containing fluid like a blister or grape. The cyst is usually filled with clear fluid. Sometimes blood clots may develop in some of the cysts and, occasionally cysts may become infected. Polycystic means there are many cysts present. In ADPKD the cysts cause the kidneys to enlarge.

How does ADPKD affect the kidneys?

The most important effect is a slow loss of kidney function. This occurs over many years and may result in the slow development of kidney failure. Both kidneys are equally affected. Kidney failure is very rare before the age of 30 and, if it develops, usually occurs from 50 to 60 years of age. Up to a third of affected individuals, however, will reach the age of 70 years without serious kidney problems. Thus not everyone with ADPKD gets kidney failure.

What makes the cysts grow?

No one knows what makes the cysts develop and grow. As a result there is no known proven treatment which will prevent cysts developing in people who have the ADPKD gene.

Is it possible to predict who will develop kidney failure?

Not everyone with ADPKD will develop kidney failure. Unfortunately it is not possible to predict who will and who won't advance into difficulties with kidney function. Furthermore, tests to tell how a patient inherits the condition are not yet available as a routine. It is important that anyone with the condition is seen regularly (about once a year) by a doctor for a check on blood pressure and the measurement of waste product levels in the blood. This will allow detection of any changes in kidney function at an early age.

Can other parts of the body be affected?

Yes. It is very common for people with ADPKD to have cysts in the liver.

These may cause a large liver but liver failure does not occur. Occasionally cysts can occur in the spleen or pancreas but these do not cause any symptoms.

What are the symptoms of ADPKD?

Some people may get no symptoms at all. Others may experience no symptoms until they develop kidney failure. Some will get a variety of problems including pain, bleeding, infection in the urine and kidney stones.

Pain - A minority of people experience pain in the loins. Usually this occurs in attacks lasting only a few hours or days and then settles for a long time. The pain can sometimes be severe requiring strong painkillers and may be accompanied by an episode of blood in the urine. Less frequently there may be a constant dull ache in the loins going on for months or years.

Blood - Blood in the urine is a very common finding in people with ADPKD. Often the blood is not visible to the naked eye but can only be detected by sensitive tests. Sometimes the urine is obviously discoloured pink, red or brown. Individuals may develop pain in the loins and blood in the urine. When this occurs it is thought to be due to the occurrence of bleeding from a cyst. Treatment in this case consists of plenty of liquids to drink, painkillers and rest. Very occasionally a blood transfusion may be necessary but the attacks will always stop eventually.

Urine infection - Studies have shown that people with ADPKD are liable to infection in the urine. Usually the attacks can be treated by antibiotics. Very occasionally infection can occur in the cysts themselves. In this case the antibiotics may need to be given through a vein to be effective. Occasionally it may also be necessary to remove any fluid or infected material from the cysts using a fine needle.

Kidney stones - Kidney stones can occur in patients with ADPKD.

Usually there are no symptoms associated with stones located in the kidney. Occasionally, the stones may move and cause symptoms such as waves of pain coming from the loin and moving around and down to the groin on the same side. Pain like this is called renal colic and may be associated with the appearance of blood or traces of stone in the urine.

How is it inherited?

The condition is hereditary which means it is caused by an altered gene. An alteration within a gene is generally referred to as a mutation. The gene mutation may be passed on from an affected parent to a child. Genes are the codes for the messages which tell the body how to develop, grow and work

normally. Each gene codes for a different message. Genes are grouped together on structures called chromosomes. Humans have 23 pairs of chromosomes. Twenty two pairs are called autosomes. The last pair are called sex chromosomes and determine the sex of an individual. The A in ADPKD stands for autosomal. This means the condition is inherited on one of the autosomes. Because the gene is not on a sex chromosome males and females have an equal chance of having the disease. The first D in ADPKD stands for dominant. This means that if a person has the abnormal gene mutation then he or she will develop cysts in the kidney.

When a child is born to a parent with the condition there is a 1 in 2 chance that the child will inherit the mutation responsible for ADPKD. This is just like tossing a coin where there is a 50% chance of getting a head and a 50% chance of getting a tail. Sometimes 5 or 6 heads may occur in a row, however, if the coin is tossed often enough eventually there will be roughly equal numbers of heads and tails. The same is true in families with ADPKD. One family may have all affected children and another have none affected but on average there will be half affected and half unaffected. Everyone who has the gene for ADPKD will eventually develop kidney cysts, although the rate of cyst development is variable from one person to another. It is important however, to realise that if a child does not inherit the gene, he or she cannot transmit the condition to their children. The ADPKD gene does not skip generations, although it may appear to do so in some families. When this appears to have occurred it is because someone with the gene has had very few symptoms and may never have known that they had the condition.

How is the diagnosis made?

A person may discover they have ADPKD in a number of ways.

Firstly, they may be screened because someone else in the family has the condition. Usually this means having a test called an ultrasound scan.

Secondly, the condition may be picked up by chance when a person is seen for another condition either by a doctor feeling enlarged kidneys when examining the abdomen or as a result of some type of scan being done because of some other abdominal problem.

Finally, the condition may be diagnosed because the patient has symptoms suggestive of kidney disease or kidney failure.

Who should be tested?

In medical terms, there are a number of important potential benefits that arise from an early diagnosis of ADPKD. People with the condition are at increased risk of a number of complications which can remain hidden but which benefit greatly from early detection and treatment. The commonest and most important of these treatable complications is raised blood pressure (hypertension). This occurs as a result of cysts in the kidneys and is responsible for premature deaths from heart attack, stroke or a further deterioration of kidney function. Occasionally, infection can develop in one or a number of kidney cysts, causing further kidney damage.

While there are some beneficial effects that may arise from an early diagnosis, there are also a number of more negative aspects that need to be considered.

Many people express concern about the potential psychological difficulties that may be encountered after learning that the condition may be present. These psychological issues may be even greater when a child is diagnosed as having ADPKD as a result of testing arranged because of the known background family history. One the other hand, some people experience considerable relief after learning as much as they can about the condition instead of having only partial understanding which often creates the potential for some more frightening misunderstandings. Occasionally, there are other surprising consequences which can arise from diagnosing ADPKD. Many people find that life insurance is more difficult to obtain and sometimes there can be employment consequences, particularly when an employer requires a medical examination prior to commencing a new job. Overall, we would suggest that it is important for each person to decide for themselves whether or not they wish to be tested bearing in mind their own particular circumstances.

Is there any treatment?

At present there is no proven treatment that will stop the cysts developing and growing. More importantly there is no proven treatment that will prevent a patient from developing kidney failure. However, there is evidence that if high blood pressure occurs as a complication of ADPKD then lowering the blood pressure will slow the rate at which the kidneys deteriorate. If kidney failure occurs, patients can be treated by dialysis or a kidney transplant and the results of these treatments are as good as with any other cause of kidney failure.

What should I do if I have ADPKD?

The important thing to remember is that most people with the condition should be able to live a normal life for many years. It is highly advisable to have an annual examination. This means having the blood pressure checked and a blood test to check on kidney function. If the blood pressure is found to be raised this can be treated by one or more drugs. Once the blood pressure is controlled it should be re-checked at frequent intervals, about once a month. This can be done by your family doctor or a nurse. The blood tests measure the level of waste products. The two main waste products are urea and creatinine. If the levels of these substances start to rise this suggests the kidney function is deteriorating. If the blood urea and creatinine are found to be raised, testing is done more frequently. If kidney function is significantly reduced then a the blood count, which checks for anaemia, and other tests to assess calcium and the bones will also be done. If found, correction of these later complications of developing kidney failure will often bring benefits such as an improvement in energy levels and sense of well-being.

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