Autosomal dominant polycystic kidney disease (ADPKD) causes cysts to develop in the kidneys and liver. The cysts are not cancerous and the fluid inside them is harmless.
In ADPKD, cysts typically begin to form in late childhood or early adulthood. Most people with ADPKD have numerous cysts in their kidneys and liver by the time they reach old age. In addition, around 10 per cent of people with ADPKD have cysts in their pancreas, although these almost never cause problems.
The cysts cause very slow damage to the kidneys that, in some people, results in kidney failure – normally during later adult life. Usually, both kidneys are affected.
At least one person in every 1,000 has ADPKD, meaning there are more than 60,000 people with the disease in the UK. It affects both sexes and all races equally.
The cysts form at random and can appear anywhere inside the kidneys and liver. As the cysts get bigger they cause the affected organs to enlarge. The larger they get, the more space they take up and as a result, the tummy may become swollen and patients may experience abdominal pain.
Figure One shows an ADPKD kidney in comparison to a normal kidney.
Figure One: An ADPKD and an unaffected kidney. Photo courtesy of the PKD Foundation.
Patients may also notice blood in their urine (haematuria). This happens when a tiny blood vessel in the wall of a cyst breaks, causing the cyst to bleed. Around 40 per cent of people with ADPKD experience pain – usually in their sides or their back – or blood in their urine.
ADPKD causes high blood pressure (hypertension) and this sometimes develops before any cysts have grown. Mild to moderate hypertension rarely causes any symptoms but it increases the risk of heart disease and stroke, and can cause kidney function to decline more quickly. It is therefore very important that high blood pressure is diagnosed and treated early.
Less commonly, kidney cysts can become infected. This is usually very painful and typically accompanied by other symptoms, such as sweating, fever and high temperature. Cyst infections sometimes occur following a bladder or urinary tract infection (UTI). If a UTI is suspected it is important to see a doctor and get treatment as soon as possible. People with ADPKD are also a little more likely than the general population to develop kidney stones.
More rarely, ADPKD can cause swelling of one or more of the small arteries in the brain. This can sometimes result in bleeding into the brain (a brain haemorrhage), which can be dangerous. However, because this is so rare people with ADPKD are only screened for this complication if they or a member of their family have previously had a brain haemorrhage.
Liver cysts tend to be larger in women and, although they can be uncomfortable if they grow very large, they almost never cause liver damage
ADPKD is typically diagnosed using an ultrasound scan, which detects the presence of cysts.
Blood tests will be needed to monitor changes in the levels of creatinine and other substances in the body, and blood pressure will need to be checked regularly so that high blood pressure can be treated effectively. Patients will be under the long-term care of a specialist renal (kidney) doctor, who they will probably need to see about once a year. If blood tests show evidence of kidney damage then patients may need to be seen more frequently.
Most people with ADPKD live completely normal lives with no symptoms almost all of the time. A diagnosis of ADPKD does not prevent people from working, having children, going on holiday, taking exercise or drinking alcohol as normal. However patients should avoid violent contact sports (such as boxing or rugby) if they have large cysts that are visible on a scan.
There is currently no cure for ADPKD, but there are things that patients can do to protect their kidneys and stay as healthy as possible.
- Avoid smoking – Smoking damages the blood vessels in the kidneys and accelerates kidney damage.
- Control blood pressure – High blood pressure is harmful to the kidneys and increases the risk of stroke and heart disease. Conversely, damage to the kidneys makes high blood pressure worse, so it is vital that blood pressure is closely monitored and high blood pressure is treated early. Blood pressure readings taken in a clinic do not always reflect a patient’s blood pressure the rest of the time, so it is a good idea to buy a blood pressure machine and check blood pressure at home as well.
- Watch your diet – balanced diet is important for everyone to stay healthy. It’s also important to limit how much salt patients have in their diet because eating salt makes high blood pressure worse.
- Take exercise – Try to take regular exercise and be active. This helps prevent weight gain and can help to control blood pressure.
- Drink plenty of water – There is evidence to suggest that the body’s response to dehydration increases cyst growth. This response can be minimised by drinking plenty of water to stay hydrated.
- Avoid NSAIDs – Non-steroidal anti-inflammatory drugs (NSAIDs) are a class of medication commonly used to relieve pain, reduce inflammation and bring down a high temperature. They include ibuprofen and diclofenac. NSAIDs can cause scarring in the kidneys so it is best for ADPKD patients to avoid them and ask their doctor or pharmacist to suggest safer alternatives.
Regular information events are held throughout the year.
Previous events have been held in London (July 2017), Bristol (March 2017), Salford (November 2016), Sheffield (September 2016) and Birmingham (January 2016). Clinical members of the ADPKD Rare Disease Group attend and talk at these events.
Each kidney is made up of about a million filtering units called nephrons. Each nephron consists of a filter (glomerulus) connected to a tube (tubule). As the nephrons filter the blood, nutrients are removed and returned to the body. Excess fluid is concentrated and expelled as urine. In ADPKD, cysts can develop in every part of the tubule. These arise as out-pushings of the tubule, which multiply and grow until they stop the nephron from working. Figure Two shows a normal nephron and one with cysts.
Figure Two: A normal and a polycystic nephron. Figures courtesy of Professor Pat Wilson
How is it inherited?
ADPKD is an inherited disease, meaning it is passed on from parents to their children through their genes. Genes are the instructions our cells need to make our body parts and organs. We all have two copies of each gene, one from each of our parents. ADPKD is caused by an abnormality – often called a mutation – in one of two genes involved in ADPKD. These genes are called PKD1 and PKD2. Most people get the disease when they inherit a faulty copy of one of these from a parent with ADPKD. Sometimes, though, a new genetic change occurs spontaneously, causing the disease in a person with healthy parents who do not have the mutated gene. This new mutation can then be passed onto the next generation. You only need to receive one mutated gene copy to have ADPKD. So, a person with the disease has a one in two (50 per cent) chance of passing the disease on to each of their children, depending on whether they pass on their faulty or normal copy of the gene. If a child inherits the normal copy from an affected parent, then they (and any children they go on to have) will not have the disease. This is known as autosomal dominant inheritance and can be seen in Figure Three below. In this example it is the mother who has the condition, but males and females are at equal risk of inheriting the disease.
Figure Three: Autosomal dominant inheritance a = faulty gene A = normal gene
The ADPKD Rare Disease Group (RDG) is working with international partners with the aim of finding new and improved treatments, and to empower patients. A first step is to compile the symptoms, treatments used and markers of ADPKD. To do this the RDG are registering patients with this condition in the National Rare Kidney Disease Registry (RaDaR). The database will be used to find suitable participants for future research trials into the effectiveness of new treatments. If you are interested in finding out more about RaDaR or the activity of the RDG please visit the ADPKD RDG page.