Around 12 million people worldwide suffer from cystic kidneys, a disease that is 50% likely to be inherited. Around 100,000 people are affected in Germany, experts assume that the number of unreported cases is significantly higher. Nevertheless, the ADPKD, the so-called cystic kidneys, is largely unknown to the public. So far, only symptoms and any accompanying diseases that may have occurred can be treated. There is therefore an urgent need for disease-related, kidney-specific therapy options to slow the loss of kidney function and to give the patient a new perspective on life.
ADPKD is hereditary, affects men and women equally often and is inherited in an autosomal dominant manner. It is now known that there are changes in chromosome 16 in around 85 percent. This altered gene leads to the formation of cysts in the kidneys, i.e. liquid-filled spherical cavities, which increase in size and size. Cyst formation can also occur in other organs. The liver is primarily affected. In the majority of patients, kidney failure occurs before the age of 60 and the patient needs a transplant or dialysis.
Cysts in the kidneys displace healthy kidney tissue and gradually restrict kidney functions. This manifests itself with the following symptoms:
The symptoms usually manifest themselves between the 30th and 50th year of life. The first sign is usually high blood pressure, which is difficult to control. Many organ systems are affected in the course of the disease, such as the liver, brain, heart and digestive system.
The following complications are possible:
The most common form of polycystic kidney disease is inherited in an autosomal dominant manner (see box below). It also carries this inheritance in its name. ADPKD stands for "Autosomal dominant polycystic kidney desease", or in German, Autosomal dominant polycystic nephropathy.
Information on the frequency of the corresponding gene changes fluctuate between one to five affected people in 2000 people in our population. About ten percent of all people who regularly need blood washing (dialysis) because of kidney failure suffer from ADPKD.
In addition, there are various other forms of polycystic kidney disease with different causes and courses. Some are characterized by congenital kidney failure, others only become noticeable later. Each of these forms is rare in itself. One of them is the autosomal recessive polycystic nephropathy ARPKD (Autosomal recessive polycystic kidney desease). ARPKD is a very serious illness.
Kidney cysts are often discovered accidentally during an ultrasound examination (sonography). Ultrasound is a very good way of distinguishing cysts from other tissue changes, such as kidney tumors, because they appear as dark, fluid-filled cavities.
The sonography of the kidneys is an easy to carry out and completely painless and uncomplicated examination for the patient. If the kidneys are greatly enlarged, the doctor can sometimes even feel them with the hands during the physical examination in the flank area.
Computed tomography or magnetic resonance imaging can also be performed.
During the urine test, red blood cells and proteins in the urine indicate kidney damage. If there are also white blood cells in the urine, there is also an inflammation. Blood tests provide information about the current kidney function.
By taking kidney tissue (biopsy) and examining it, the doctor can distinguish between ARPKD and ADPKD, for example. Molecular genetic analysis can help identify the changed genes.
It is also important to examine patients with cystic kidneys for other cysts in other organs as well as for aneurysms in the main artery and in the brain vessels.
In patients with cystic kidneys, regular examinations for consequential damage are recommended. Above all, this includes the early detection of high blood pressure and its consequent treatment. Poorly or untreated hypertension contributes significantly to a rapid loss of kidney function.
Examinations for urinary tract infections are also useful in order to identify and treat them early.
Treatment is not required for simple kidney cysts that do not cause discomfort or complications.
Patients with larger cysts or cystic kidneys may need pain-relieving therapy for pain in the kidney area (so-called flank pain).
If the symptoms are not sufficiently alleviated, it is possible with large cysts to aspirate the contents (puncture), to clear the cysts or, if necessary, to remove them completely (cyst resection). You always try to keep the functioning kidney tissue as good as possible and not damage it. Surgery is always necessary if the cysts tear, if they cause serious infections or become malignant.
The more extensive the operation, the more complications can arise. This can lead to injuries to other organs, nerves and blood vessels that cause bleeding and subsequent bleeding. Injuries to the urinary organs (for example, a ureter) can cause urinary disorders and urination disorders.
In patients with congenital or inherited cystic kidneys, regular blood pressure monitoring should be carried out and normalization of blood pressure should be aimed at in order to slow down the decline in kidney function. Because with high blood pressure, kidney function deteriorates faster. If the blood pressure is too high, hypotensive agents are used in cystic kidneys. Dialysis is necessary for kidney failure. Ultimately, healing of the cystic kidneys is only possible through a kidney transplant.
About half of those with ADPKD suffer from kidney failure within 10 to 20 years, so dialysis is necessary. This is the case for most patients after the fifth to sixth decade of life. The disease progresses particularly quickly if it appears very early, i.e. under the age of 30. Men are more often affected by such courses than women.
Poorly controlled high blood pressure and cigarette consumption have a disadvantage.
The most dangerous complication of the disease is the rupture of an aneurysm of the brain vessels. If an aneurysm is known, it can be considered together with the attending physician whether an intervention that switches off the aneurysm makes sense. It is important to carefully weigh up possible advantages and risks. Aneurysms at risk of rupture should be closed.
In 2016, the European Medicines Agency (EMA) approved the first drug specifically for the therapy of ADPKD. The vasopressin 2 receptor antagonist tolvaptan reduces the concentration of cAMP in renal epithelial cells; the signaling molecule is believed to play an important role in cyst formation. In a randomized, double-blind, placebo-controlled, three-year study, tolvaptan in the kidney slowed the increase in volume - by 2.8% instead of 5.5% per year - and the loss of function. Verum therapy, however, was stopped prematurely more often than placebo treatment due to problems with increased water excretion and due to the increase in liver enzymes. According to the EMA, the risks outweigh the benefits of the therapy. The prerequisite is that the patients drink a lot of water during the treatment and receive regular liver checks.