Kidney Cyst | Specialists and Information

Medicine distinguishes four different types of kidney cysts (according to Bosniak):

• Types 1 and 2: Benign, almost never cause problems, and have no walls or only very thin walls. In rare cases, such a kidney cyst can grow very large and require treatment.
• Type 3: The kidney has an irregular or thickened wall. Since it can develop into a malignant cyst, surgical intervention is always recommended.
• Type 4: Malignant disease (kidney cancer).

No specific causes are known for the sporadic development of individual kidney cysts. Polycystic kidney disease is usually hereditary and is inherited in an autosomal dominant pattern. The chance that an affected parent will pass on the defective gene is 50%. If this occurs, the child will also have the condition. It does not matter whether the child has also received a healthy gene from the other parent.

How autosomal dominant inheritance works. The genetic defect on the chromosome is marked in red

Kidney cysts can also form as a result of long-term dialysis.

A single kidney cyst often goes unnoticed for a lifetime because 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 frequently cause symptoms such as back pain, blood in the urine, or high blood pressure.

The following symptoms are typical of polycystic kidneys:

• Kidney pain
• High blood pressure
• Blood in the urine
• Frequent urinary tract infections
• Intestinal diverticula (outpouchings)
• Cysts in other organs (e.g., liver, spleen)
• Aneurysms (dilations of blood vessels)
• Heart valve defects (rare)

The larger the kidney cysts are, the more pronounced the symptoms are.

A kidney cyst approximately 30 mm in size as seen on a CT scan. The cyst is marked in the two images below and is clearly visible

Single kidney cysts that cause no symptoms are usually discovered by chance. The doctor can determine the size and type of the cyst using imaging techniques. These include

• ultrasound (sonography),
• less commonly computed tomography (CT), or
• X-ray examinations.

For type 3 or 4 kidney cysts, a CT scan with contrast dye is used to rule out a malignant tumor. A nephroscopy (renoscopy) also provides additional information about whether the cyst is a kidney tumor. Blood and urine tests are also helpful methods that can indicate possible urinary tract infections and impaired kidney function.

Treatment for a kidney cyst depends on the size of the cyst and whether it causes symptoms. Individual, harmless kidney cysts usually do not require treatment.

To date, there is no curative treatment for polycystic kidneys. Treatment is therefore aimed at relieving symptoms:

• blood pressure-lowering medications for high blood pressure: Since high blood pressure puts additional strain on the kidneys, regular monitoring of blood pressure is very important in cases of kidney cysts
• A healthy lifestyle: For example, patients should quit smoking, avoid being overweight, and aim for a low-sodium diet
• Antibiotics for urinary tract infections

If a single cyst is large enough to displace kidney tissue, surgical removal or aspiration may be performed. During aspiration, the doctor drains the fluid from the cyst using a thin hollow needle. The doctor then seals the drained cyst using a chemical. This minimally invasive method has the advantage of requiring no incisions; however, kidney cysts often recur.

Another minimally invasive method for removing kidney cysts involves ablating the cyst wall through incisions only a few millimeters in size. To prevent the cysts from recurring, the remaining edges of the cyst are ablated using an electric current.

If the kidney cysts impair kidney function or cause kidney failure, blood must be purified through dialysis. In the long term, a kidney transplant is necessary in this case.