Autosomal dominant polycystic kidney disease

This is an inherited condition in which fluid-filled sacs — cysts — keep appearing in the kidneys and slowly growing throughout life. The faulty gene is there from birth, yet for decades nothing is felt: the cysts are far too small to get in the way. The first trouble usually arrives between the ages of thirty and fifty, once the enlarging cysts have crowded out the working tissue, the kidneys have swollen to several times their normal size and filter the blood less well. It is the commonest inherited kidney disease: roughly one person in every one thousand to two and a half thousand has it.

What is actually passed on

The fault nearly always sits in one of two genes. Changes in PKD1 are found in about three quarters of those affected and changes in PKD2 in one in seven; in the rest, rarer genes are responsible or no fault can be identified. The difference matters in practice: with PKD1 the kidneys fail on average 15 to 20 years earlier, even though the symptoms are the same.

The word "dominant" means that one faulty copy of the gene out of the two a person carries is enough to cause the disease. Each child of an affected parent therefore has a one in two chance of inheriting it, regardless of how many children in the family already have it and regardless of sex.

In roughly one person in ten the fault arises for the first time, with no affected relatives at all; more often still the family history is simply unknown, because a relative died young or their illness went by another name. No family history does not rule the diagnosis out. There is also a second, far rarer form — the recessive one: it requires a faulty gene from both parents, shows itself in infancy and behaves quite differently.

How the disease announces itself

Pain and high blood pressure usually come first, rather than the things people expect from kidney trouble.

• Pain in the loin, the flank or the abdomen. Dull and constant when it comes from the weight of enlarged kidneys; sudden and sharp when it comes from bleeding into a cyst or from a stone.
• Blood in the urine. Sometimes visible to the eye, sometimes only in a test. It usually settles by itself within a few days, but it is worth showing to a doctor, because other conditions look the same.
• High blood pressure. It appears early, not rarely before the age of thirty and long before any test results worsen.
• Kidney stones. One person in four or five with the condition gets them, noticeably more often than in the general population.
• Urinary infections. They are no more frequent in themselves, but they travel upwards more easily into the kidney and into the cysts, and that is a serious matter.

Kidney function stays normal on blood tests for a long time, even when the organs are already greatly enlarged. A "good creatinine" therefore does not mean the disease has stopped moving: kidney volume on a scan is a better guide to that.

Blood pressure is the part you can change

The cysts press on the blood vessels of the kidney, the kidney responds by releasing substances that push the pressure up, and high pressure then finishes off the kidney tissue that is left and damages the heart. Breaking that circle is the single most effective thing available.

That is why blood pressure is measured at home and regularly, rather than once a year at an appointment, and why treatment starts early. The mainstay is usually a drug that blocks the renin-angiotensin system — an ACE inhibitor or an angiotensin receptor blocker. The particular drug and the target figures are chosen by a doctor, and the targets here are often stricter than usual. Salt is kept to around five grams a day: that is one teaspoon covering everything eaten in the day, bread, cheese and cured meat included.

When help cannot wait

Most of what this disease does can be dealt with in an unhurried way, but some situations are counted in hours. Call your local emergency number (112 in much of Europe) if:

• the worst headache of your life comes on suddenly, like a blow to the head, especially with vomiting, a stiff neck, discomfort in bright light or confusion: this is how a burst brain aneurysm presents;
• the face droops, an arm or leg goes weak, or speech is lost;
• severe flank pain begins together with a high temperature and shivering;
• the urine turns deep red with clots and the bleeding will not stop;
• abdominal pain starts abruptly and keeps getting worse.

Contact a doctor the same day if a temperature comes on alongside burning when passing urine, if flank pain and cloudy urine appear, if blood in the urine lasts longer than a week, or if the amount of urine drops sharply. An infection that has settled inside a cyst is hard to treat, because antibiotics penetrate it poorly, and it must not be left.

What happens outside the kidneys

The disease does not stop at the kidneys.

• Cysts in the liver. The commonest finding outside the kidney. They rarely disturb how the liver works, but when there are many they cause heaviness, a bloated feeling and getting full quickly at meals. Women have more of them and they grow faster, because female sex hormones play a part; hormonal contraception is therefore worth discussing with a doctor.
• Brain aneurysms. About one affected person in ten has one, several times more often than in other people. While an aneurysm is intact it stays silent; the danger is that it bursts.
• Heart and blood vessels. Years of high blood pressure raise the risk of heart attack and stroke; changes in the heart valves and widening of the first part of the aorta also occur.
• Hernias and diverticula. Groin and umbilical hernias, and pouches in the wall of the large bowel, turn up more often than usual.

A hard blow to the abdomen or the lower back can tear a cyst inside an enlarged kidney and cause bleeding, so contact sports are not advised once the kidneys are large.

How the diagnosis is made, and whether relatives should be checked

The main test is an ultrasound scan of the kidneys. The diagnosis does not rest on cysts simply being present, but on how many there are for a person's age: in a young adult a handful of cysts already points to the disease, whereas in an older person the odd cyst is an ordinary finding that comes with age. A CT scan shows small cysts better and allows kidney volume to be measured, which is what tells you whether the disease is moving fast. Blood pressure is checked as well, along with the urine for blood and protein and a blood test to calculate the filtration rate. Genetic testing is not needed by everyone: it earns its place when the picture is unclear, when a relative is being prepared to donate a kidney, and when a pregnancy is being planned.

Screening healthy relatives was once considered pointless, because there was nothing to slow the disease with. That argument is weaker now: a treatment exists that slows cyst growth, and controlling blood pressure early lengthens the life of the kidneys by itself. Against it stand the practical consequences of carrying a diagnosis and the worry it brings. A sensible middle ground is to offer testing to an adult and let them decide; children without symptoms are not usually scanned, though their blood pressure is measured from an early age, because it begins to climb in childhood.

What is in your hands day to day

The disease cannot be cured, but the speed at which it moves depends on everyday habits more than people assume.

• keep blood pressure at the agreed target and write the home readings down;
• use less salt: salt directly drives both the pressure and the growth of the cysts;
• drink enough water, spread evenly through the day: it cuts stone formation and may hold the cysts back;
• do not smoke and keep weight in a healthy range, as smoking speeds up the loss of kidney function;
• do not take anti-inflammatory painkillers for long stretches or without advice; paracetamol is the first thing to try for pain;
• run new medicines and any scan involving contrast past a doctor who knows about the kidney disease;
• plan pregnancy ahead of time: this condition carries a higher risk of pre-eclampsia and calls for closer monitoring.

The old advice to give up coffee has not held up: a moderate amount of coffee does not speed the disease along.

Treatment, and what happens if the kidneys fail

There is no drug that stops the disease. There is one that slows cyst growth and the loss of kidney function, and it works by blocking the hormone vasopressin. It is offered to people whose disease is moving quickly, and it does not suit everyone: on treatment a very large volume of urine is produced, thirst becomes hard to live with, and the liver has to be watched with regular blood tests. A kidney specialist makes that call. The rest of treatment deals with problems as they arise: blood pressure, pain, stones, infections; a large painful cyst is sometimes drained through the skin.

About half of those affected need kidney replacement treatment by the age of sixty. It does not happen overnight: function is lost over years, and the plan is discussed well in advance. There are two options, dialysis and a kidney transplant. A transplant usually gives the better life, and the kidney can come from a living donor, including a relative, once testing has confirmed that they are healthy. An older person with serious other illnesses has every right to choose a third path — to decline dialysis in favour of care aimed only at feeling as well as possible.

Online consultation

In an online appointment a doctor can go through the family history and explain which relatives it makes sense to test, look over the home blood pressure record and the test results, say which investigations are needed now and which are unnecessary, warn about medicines best avoided, and help you tell which symptoms can be watched at home and when it is time to go to hospital.

This material is for information only and does not replace medical advice.