Medicine distinguishes between four different types of renal cysts (according to Bosniak):
- Type 1 and 2: Benign, almost never cause problems and have no or only extremely thin walls. In rare cases, such a kidney cyst becomes very large and must be treated.
- Type 3: The kidney has an irregular or thickened wall. As it can develop into a malignant cyst, surgery should always be performed.
- Type 4: Malignant disease(kidney cancer).
Computed tomography image of a kidney cyst measuring approx. 30 mm. The cyst is marked and clearly recognizable in the two images below
There are no known specific causes for the accidental development of individual kidney cysts. Cystic kidneys are usually hereditary and are inherited in an autosomal dominant manner. There is a 50% chance that a diseased parent will pass on the defective gene. If this occurs, the child also suffers from the disease. It does not matter whether it has also received a healthy gene from the other parent.
How autosomal dominant inheritance works. The genetic defect on the chomosome is marked in red
Kidney cysts can also form as a result of many years of dialysis.
A single kidney cyst often goes unnoticed for a lifetime as it does not cause any symptoms. If a cyst becomes very large, it can cause pain in the kidney or abdominal area. In addition, large cysts often cause symptoms such as back pain, blood in the urine or high blood pressure.
The following symptoms are typical of cystic kidneys:
- Kidney pain
- high blood pressure
- blood in the urine
- Frequent infections of the urinary tract
- Intestinal diverticula (protrusions)
- Cysts in other organs (e.g. liver, spleen)
- Aneurysms (dilation of blood vessels)
- Heart valve defects (rare)
The larger the kidney cysts are, the more pronounced the symptoms are.
Individual kidney cysts without symptoms are usually only discovered by chance. The doctor can determine the size and type of cyst using imaging techniques. These include
- Ultrasound (sonography),
- less frequently computer tomography (CT) or
- X-ray examinations.
In the case of type 3 or 4 renal cysts, a CT scan with contrast medium is used to rule out a malignant tumor. A renal endoscopy (renoscopy) also provides information as to whether it is a kidney tumor. Blood and urine tests are also helpful methods that can indicate possible urinary tract infections and impaired kidney function.
The doctor can use ultrasound to diagnose kidney cysts
The treatment of a kidney cyst depends on how large the cyst is and whether it causes symptoms. Single harmless kidney cysts do not normally require treatment.
A causal therapy for cystic kidneys is not yet possible. Treatment is therefore aimed at alleviating the symptoms:
- antihypertensive medication for high blood pressure: as high blood pressure puts additional strain on the kidneys, regular pressure checks are very important in the case of renal cysts
- healthy lifestyle: patients should, for example, stop smoking, avoid being overweight and aim for a low-salt diet
- Antibiotics for urinary tract infections
If an individual cyst is so large that it is displacing kidney tissue, surgical removal or puncture is possible. During a puncture , the doctor draws the fluid out of the cyst using a thin hollow needle. The drained cyst is then sealed with a chemical. This minimally invasive method has the advantage that no incisions are necessary, but the kidney cysts often return.
Another minimally invasive method for removing kidney cysts involves removing the cyst wall through incisions just a few millimetres in size. To prevent the cysts from returning, the remaining edges of the cyst are cauterized with an electric current.
If the kidney cysts impair kidney function or cause it to fail, the blood must be purified using dialysis. In this case, a kidney transplant is necessary in the long term.
