Renal cysts and cystic kidneys

Overview: What are renal cysts and cystic kidneys?

Cysts are cavities filled with fluid and surrounded by a capsule. They can develop in almost all tissues and organs of the body – including the kidneys. Individual kidney cysts are usually acquired by a person in the course of his or her life. As a rule, they are harmless and do not affect kidney function and health. They usually do not cause symptoms and do not require treatment.

It is different with the so-called cystic kidneys. Affected individuals have very large numbers of cysts in both kidneys, which gradually impair the vital filtering function of the organs. Experts also refer to cystic kidneys as polycystic kidney disease (PKD). The disease is hereditary and parents pass on the predisposition to their offspring – altered genes therefore play the decisive role in its development. Doctors always have to treat cystic kidneys because kidney function continues to decline – even to the point of kidney failure.

There are two main forms of cystic kidneys:

• Autosomal dominant polycystic kidney disease (ADPKD) – it is the most common form.
• Autosomal recessive polycystic kidney disease (ARPKD) – it is much less common. It already affects children and means a low life expectancy.

In most cases, physicians discover ADPKD by chance during a routine examination, such as an ultrasound. This is because the symptoms usually begin in young adulthood. Affected individuals usually experience pain in the kidney area, back, flanks or groin.

Treatment is aimed at relieving symptoms and slowing the progression of the disease. Medications, blood purification (dialysis) and finally a kidney transplant are used.

Renal cysts and cystic kidneys – frequency and age

There are no precise figures on the incidence of renal cysts, which are usually harmless. They often go undetected because they do not cause problems. Cystic kidneys are among the most common hereditary diseases: In Switzerland, about 10,000 people are affected. More than six million people worldwide have cystic kidney disease.

Die häufigste Form der Zystenniere ist die autosomal-dominante polyzystische Nierenerkrankung (ADPKD). There is a 50 percent chance that parents will pass on the defective hereditary trait in ADPDK to their child. Cystic kidneys are congenital in about two-thirds of those affected, and babies are already born with the genetic defect. Very rarely, the disease occurs without affecting other family members – in this case, the gene alteration occurs directly after fertilization.

Men and women develop ADPKD at approximately the same rate. Most often, cystic kidneys appear in adulthood between the ages of 30 and 40. Around the age of 50, patients must expect the final loss of kidney function.

Autosomal recessive polycystic kidney disease (ARPKD) is much less common. It additionally interferes with breathing, which often means early death in the first months of life.

Renal cysts and cystic kidneys: Causes

The causes of isolated renal cysts are unknown. In contrast, cystic kidneys involve genes. In autosomal dominant polycystic kidney disease (ADPDK) , one of the so-called PKD genes is altered:

• PKD1: 85 to 90 percent of cases, the defect is located on chromosome 16.
• PKD2: 10 to 15 percent of cases, the alteration is located on chromosome 4.
• In addition, researchers have identified another gene, the DZIPL1 gene.

The two PKD1 and PKD2 genes control the production of polycystin-1 and polycystin-2. Their exact function is not yet known, but the two substances are probably very important for the kidney structure. If they do not function, a large number of cysts develop in both kidneys. In most cases, a PKD1 mutation means a more severe course because kidney failure sets in earlier.

The mode of inheritance is autosomal dominant. This means that the altered gene must be located on only one of the two chromosomes – either the maternal or the paternal. Therefore, the probability for a child to inherit the genetic defect is 50 percent.

The cause of autosomal recessive polycystic kidney disease (ARPKD) lies in another gene: the polycystic kidney and hepatic disease 1 gene(PKDH1). It is responsible for the formation of the protein fibrocystin. Its task in the body has also not yet been precisely clarified. In autosomal recessive inheritance, the mutated gene must be present on both the maternal and paternal chromosomes. Statistically, the probability of contracting the disease is 25 percent.

Symptoms: Renal cysts and cystic kidneys

Individual kidney cysts are usually harmless and do not cause any symptoms. Most do not notice the fluid-filled blisters in their kidney. They also usually do not interfere with kidney function. However, if a kidney cyst grows extremely, it can cause pain, such as in the flank or back. Depending on the configuration of the renal cysts, individual renal cysts may also require further evaluation, as there are also cystic renal tumors.

In cystic kidneys, countless cysts form with increasing years of life and continue to grow. As a result, the kidneys also enlarge and gradually lose their function. How fast the kidneys enlarge varies from individual to individual. Patients with very large kidneys often also have more severe symptoms. In about half of those affected, kidney failure eventually develops.

Autosomal dominant polycystic kidney disease may not cause symptoms for a long time, but eventually makes it noticeable with the following symptoms:

• Pain in the flanks, back, groin, or abdominal and stomach areas
• High blood pressure (hypertension) – the renal cysts probably press on a renal vessel.
• Blood in the urine (hematuria) – the urine turns reddish because the cysts are bleeding.
• Repeated urinary tract infections – women are affected more often than men. The reason for urinary tract infections is that cysts are an ideal breeding ground for bacteria.
• Infections of the renal cysts, such as those caused by bacteria
• Kidney stones – cysts can interfere with urine flow and crystals form more easily.

According to a survey by the PKD Charity, many ADPKD patients also suffer from general symptoms, such as fatigue, tiredness, cramps in the legs or an increased abdominal girth. Family, social and sexual life is also affected for many.

In addition, ADPKD is often not confined to the kidneys. Cysts can also form in other organs and cause further symptoms. For example, cysts are particularly common in the liver, but also in the pancreas and spleen. In addition, cystic kidneys can also affect the heart, brain and digestive tract.

In autosomal recessive polycystic kidney disease (ARPKD), symptoms begin much earlier, usually in childhood. This is often accompanied by respiratory problems that can be fatal.

Renal cysts and cystic kidneys: Diagnosis with us

The diagnosis of renal cysts and cystic kidneys begins with a discussion of the patient’s medical history, the anamnesis. For example, the following questions are of interest to us:

• What complaints do you have and since when?
• How intense are the symptoms?
• Where are they located exactly?
• Do you have any known underlying diseases?
• Are there any diseases in your family, for example cystic kidneys?
• Do you take medication regularly? If yes: Which and since when?

Kidney cysts are often an incidental finding during a routine examination with us, for example an ultrasound. We can easily see on the ultrasound images if there are individual cysts in the kidneys or if the organs are riddled with multiple fluid-filled blisters. It can also reveal the size and condition of the kidneys, as well as the extent, shape and location of cysts.

During a physical examination, we palpate the kidney region and other areas of the body with our hands. Enlarged kidneys can often be palpated. Sometimes further imaging procedures follow if there is any ambiguity. These include computed tomography (CT), magnetic resonance imaging (MRI = magnetic resonance imaging) and positron emission tomography (PET/CT).

A urine test will show if there is blood in the urine. It also provides an indication of how functional the kidneys still are. Certain values play an important role, such as the glomerular filtration rate (GFR). Routine is also a blood test, which provides information about the condition of various organs. Among other things, we measure the creatinine level.

If cystic kidneys already occur in the family, a genetic test can detect the altered genetic makeup. Those affected should then monitor themselves particularly closely and have their kidney function checked. Those who decide against genetic testing should also have their kidneys and blood pressure checked at close intervals.

Renal cysts and cystic kidneys: Prevention, early detection, prognosis

The cause of individual renal cysts is not known. Therefore, you can not prevent them. Cystic kidneys, on the other hand, develop because certain genes are altered – and you have no control over your genes either. Thus, they cannot prevent either autosomal dominant or autosomal recessive polycystic kidney disease. Therefore, the general advice is to always seek medical attention promptly for symptoms such as pain in the kidney area. Blood in the urine is also always an alarm sign.

There are no specific measures for early detection of renal cysts and cystic kidneys. Often we find the cysts by chance during an ultrasound examination, which takes place for another reason. In the case of cystic kidneys in the family, there is the possibility of genetic testing. In addition, those affected should have their blood pressure checked at an early stage.

Course and prognosis in renal cysts and cystic kidneys

Isolated kidney cysts are usually harmless and do not affect kidney function or health. However, when they grow and become very large, they can cause pain, such as in the flanks or back. Then they may need treatment.

The course and prognosis of cystic kidneys vary from individual to individual. They depend on the form of the disease, the altered gene, and the size of the cysts and kidneys. The prognosis is less favorable if the kidneys are very large, hypertension is present early (under age 35), and other complications occur, such as blood in the urine or kidney stones.

In autosomal dominant polycystic kidney disease, it matters which of the two PKD genes is altered. This influences the course of the disease. For example, mutation of the PKD1 gene is often more severe than alteration of the PKD2 gene. The kidneys grow faster and lose their function more quickly. In the case of a PKD1 mutation, definitive kidney failure sets in at about age 54, and in the case of a PKD2 mutation, at age 74 on average.

About half of the patients have to expect definitive kidney failure after the age of 50. In addition, ADPKD does not stop at other organs: it can affect other organ systems such as the liver, spleen, pancreas, digestive system, heart and brain. The following complications often occur:

• chronic pain
• Blood in urine
• Kidney stones
• Hypertension
• Infections
• Brain: aneurysm (vessel outpouching) and the risk of cerebral hemorrhage (subarachnoid hemorrhage) – but the risk can be reduced by surgery.
• Heart: increased risk of chest tightness (angina pectoris), heart attack, and valvular heart disease

The course and prognosis in autosomal recessive polycystic kidney disease (ARPKD) are rather unfavorable. The reason is that many other problems are added, such as with breathing. Thus, many children do not survive the disease.

Renal cysts and cystic kidneys: Treatment

Single renal cysts do not necessarily require treatment. Unless they grow and become very large. Then they can displace or damage surrounding tissue. One treatment option is to pull the fluid out of the cyst with a fine needle and shrink it that way. This puncture relieves the adjacent tissue.

ADPKD as well as ARPKD are not (yet) curable. The aim of treatment is therefore to slow down kidney disease, maintain kidney function for as long as possible, and relieve symptoms. The therapy should also improve the quality of life and enable a largely normal daily routine. Treatment should be performed by a renal specialist (nephrologist) who has experience with the condition. Depending on the complications, doctors from other specialties may be involved in the treatment, for example liver specialists (hepatologists), heart specialists (cardiologists) or neurologists.

The following treatments are available for cystic kidneys:

• Tolvaptan: The active ingredient increases water excretion from the body. Studies have shown that tolvaptan can counteract the deterioration of kidney function, growth of cystic kidneys, kidney pain, and kidney infections. It has been approved in Switzerland for cystic kidneys since 2017.
• Antihypertensive drugs for high blood pressure, e.g. ACE inhibitors
• Painkillers if the cysts in the kidneys cause pain
• Medication for urinary tract infections, for example antibiotics, if bacteria are the culprit
• Blood washing (dialysis): An external device takes over the tasks of the kidneys, namely cleaning the blood of toxins and metabolic products. There are two types of blood purification: hemodialysis, for which you always have to go to the hospital, and peritoneal dialysis, which you can perform yourself at home. Both have advantages and disadvantages that are best discussed in detail with us.
• Kidney transplant when kidney fails: it can cure cystic kidneys. However, donor organs are also in short supply in Switzerland, which is why many patients are on the waiting list for a new organ.

Cystic kidneys – what you can do yourself

You can also do something yourself through a healthy lifestyle to prevent your kidneys from being put under further strain and increasing the symptoms. Some tips:

• Check your blood pressure regularly – it should be well adjusted to healthy levels over the long term.
• Eat healthy: Consume plenty of fruits, vegetables and whole grains. And drink enough. Be sparing with salt, which is considered a blood pressure driver. And consume caffeinated beverages only moderately.
• Move a lot in everyday life and do sports, preferably endurance sports. These include hiking, Nordic walking, swimming or cycling.
• Maintain a healthy, normal weight – being overweight or obese can exacerbate existing high blood pressure. If you are overweight, try to lose a few kilos. This is best achieved through a healthy diet, plenty of exercise in everyday life and sport.
• Give up smoking – it also has an unfavorable effect on blood pressure. If you are a smoker, try to quit smoking. Some people need several attempts to finally become a non-smoker. So don’t be discouraged by setbacks, but try again. Get professional support if you can’t do it alone.
• Make sure you have enough relaxation in your daily routine. Take regular breaks where the body can recover. Relaxation techniques such as autogenic training or Jacobson’s progressive muscle relaxation are also good.
• Take your medications regularly, such as for high blood pressure.