Polycystic kidney disease is a genetic disease that results in the development of multiple cysts in both kidneys, often also in other organs such as the liver. The gradual deterioration of kidney function is the cause of kidney pain and many symptoms, the most severe forms may require dialysis or kidney transplantation.

Definition

Polycystic kidney disease, or PKR, is a genetic disease characterized by the progressive appearance of multiple cysts in both kidneys. These cysts appear as small bags of fluid that slowly grow in size – some will grow to the size of an orange. The kidneys increase in size and their function deteriorates more or less long term.

The kidney performs an essential function of filtering and purifying the blood, the metabolic wastes being eliminated in the urine. It also plays an important role in the production of hormones and other substances essential in particular for the regulation of blood pressure. The deterioration of its functioning is expressed by pain and renal failure.

Various abnormalities affecting other organs can be associated with kidney cysts:

Liver cysts are common but do not affect its function.

Cardiac abnormalities, most often not very serious, can also be observed. In 25% of cases, these are abnormalities affecting the mitral valve.

About 8% of patients have an intracerebral aneurysm (arterial dilation), five times more than in the general population.

Other attacks are rare or exceptional:

• colon diverticula,
• cysts of the pancreas, reproductive system or arachnoid (one of the envelopes of the brain),
• male fertility disorders …

Causes

Polycystic kidney disease is caused by genetic mutations affecting different genes carried by non-sex chromosomes also called “autosomes” (inherited “autosomal”).

Two forms of the disease exist.

Autosomal dominant polycystic kidney disease

It is the most frequent form, linked mainly to mutations targeting two genes identified in the 1990s, called PKD1 (75-80% of cases) and PKD2 (15-20% of cases). It is said to be dominant because a single copy of the mutated gene inherited from one of its two parents is sufficient to cause the disease.

In about one in ten cases, the mutation occurs “de novo” in the gametes or immediately after fertilization, without the parents themselves being affected by the disease.

In 2016, a third gene involved in a rare and mild form of the disease was identified.

Autosomal recessive polycystic kidney disease

Much rarer, it is due to the mutation of a gene called PKHD1. The disease is expressed only when one inherits two mutated copies of the gene, one from one’s father and the other from one’s mother (so-called recessive inheritance). 

It is a serious illness because it affects young children and can be fatal.

Diagnostic

The diagnosis is based on family history and imaging tests.

Ultrasound is the simplest and cheapest examination, sufficient to detect kidney or liver cysts 4-5 millimeters in diameter. In the forms of the disease of early revelation, it makes it possible to highlight large kidneys with a typical appearance from the first days of life (or even from the second fetal ultrasound in the event of recessive polycystosis). But in the majority of patients, before the age of 30 or 40, the cysts are too small to be seen. 

The MRI, more rarely the scanner, are used to detect the disease earlier.

The identification of the mutation in question (genetic diagnosis) can be carried out by some laboratories.

The people concerned

Autosomal dominant polycystic kidney disease is one of the most common genetic diseases, and the most common inherited kidney disease, affecting both men and women. At least one in 1 people would be affected, ie 000 to 80 people in France.

Autosomal recessive polycystic kidney disease is thought to affect approximately one in 20 children.

Hypertension artérielle

Very common as in other chronic kidney diseases, it is one of the earliest symptoms, which can occur as early as childhood or adolescence. It is often moderate.

The other symptoms associated with kidney cysts usually appear in adulthood.

pain

Kidney cysts cause pain in most people.

The sharp pains may be due to an infection, bleeding from a cyst, or a displacement of a kidney stone.

The chronic pain are localized or diffuse (lower back, abdominal or flank pain). Associated with a feeling of heaviness, they are linked to the pressure exerted by the cysts.

Blood in the urine (hematuria)

The rupture of a vessel in the wall of a cyst or the displacement of a cyst can lead to the presence of blood in the urine. It is a frequent symptom, which occurs at least once in the life of half of the patients. Although spectacular (the urine is red to dark brown), it is often benign. 

Other kidney problems

• Kidney stones
• Urinary tract infections

Insuffisance rénale

It most often appears in people in their forties. The deterioration of renal function is gradual and results in a series of disorders. At the stage of end-stage renal disease, the kidneys have lost more than 85% of their function, which is life threatening. About 500 patients reach this stage each year in France.

Non-renal complications

The main symptom is the enlargement of the liver, seen especially in women. It is associated with pain and organ compression.

It is also the prolapse of the mitral valve, it is no longer tight. It can cause a heart murmur, pain, palpitations.

An aneurysm can be responsible for localized headaches or eye disorders. The danger lies in the ruptured aneurysm, which is a medical emergency. 

There is currently no specific treatment.

Hygienic-dietetic measures

To protect kidney function as long as possible, we recommend avoiding smoking, staying hydrated, keeping a healthy weight and adopting a diet low in salt and protein. Certain drugs that are toxic to the kidneys, especially anti-inflammatory drugs, should be avoided.

If there is blood in the urine, rest and increased fluid intake are usually sufficient to remedy the situation.

Global support

Regular monitoring is carried out to control the various symptoms (pain, kidney stones, etc.) and complications. High blood pressure should be monitored and treated. Surgical removal of symptomatic hepatic cysts is possible. It is rarely a solution for kidney cysts.

Treatment of end-stage renal disease

At the stage of end-stage renal failure – most often between the ages of 50 and 60 for carriers of the PKD1 gene, later for carriers of the PKD2 gene – it becomes necessary to compensate for the deficiency in renal function by resorting to dialysis. and / or kidney transplantation.

In France, around 15% of kidney transplants are performed in patients with polycystic kidney disease. The main complication is transplant rejection. The results of transplants have improved and today around 65% of grafts are still functional 10 years after the transplant.

Search

Treatments to curb the growth of cysts are being developed and represent hope for patients.