Simple Kidney Cysts
Simple kidney cysts are fluid-filled sacs that form in your kidneys. These cysts often don’t affect how the kidneys function. Simple kidney cysts are very common and become more common as people age. In rare cases, they need treatment. Most people don’t even know that they have them.
Understanding the kidneys
The kidneys are 2 bean-shaped organs near the middle of your back. They filter large amounts of blood each day. They also help control the fluid and salts (electrolytes) in your blood. They release waste products through your urine. The kidneys have tiny tubules. These structures collect newly formed urine. Cysts may result when the tubules get blocked. Small sacs sometimes form on the tubules. These may detach and become simple kidney cysts.
What causes simple kidney cysts?
Researchers are not sure what causes simple kidney cysts. You might have a single kidney cyst. Or you might have more than one. You might have them on only one kidney or on both of them. In most cases, a person has only one cyst. Over time, the cyst may slowly increase in size.
Some health conditions can cause kidney cysts to grow. For example, a person with polycystic kidney disease develops a large number of kidney cysts. Too many cysts can keep the kidney from working properly. Polycystic kidney disease is genetic. It's a different problem from simple kidney cysts.
Other health conditions that can cause simple kidney cysts include:
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Chronic kidney disease
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Dialysis for chronic kidney disease
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Medullary cystic kidney disease
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Autosomal dominant polycystic kidney disease
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Von Hippel-Lindau disease
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Tuberous sclerosis complex
If you smoke or have high blood pressure, you may have a higher risk for a simple kidney cyst.
Symptoms of simple kidney cysts
Simple kidney cysts often don’t cause symptoms. In rare cases, they may cause symptoms such as:
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Blood in your urine if the cyst bursts
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Pain in your upper belly or back if the cyst bursts
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Fever and chills if the cyst is infected
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High blood pressure if the cyst compresses the rest of the kidney
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Trouble peeing if the cyst blocks the tube that sends urine from the kidneys to the bladder (ureter)
A simple kidney cyst often doesn’t greatly affect kidney function unless it blocks the ureter. More commonly, a cyst may cause a slight drop in kidney function that doesn’t cause any problems or symptoms.
Diagnosing simple kidney cysts
Simple kidney cysts are often first found with an imaging test that was done for another reason. Your healthcare provider will ask about your health history and symptoms. They will also give you a physical exam.
It's important to tell simple kidney cysts from complex cysts. Complex cysts are a different kind of cyst that may be cancer. A complex cyst needs to be removed. For this reason, you may need tests such as:
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Kidney ultrasound
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Kidney CT scan, if a detailed picture of the cyst is needed
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Kidney MRI, if more information is needed about the cyst
A radiologist will look at these pictures to see if your kidney cyst is simple or complex. A cyst may be rated with the Bosniak system. This has 5 categories based on how the cyst looks. If your cyst is a category 1, you likely won’t need any more tests. A kidney cyst with a higher rating may need more tests or treatment. A category 5 cyst is most often linked with cancer.
Your healthcare provider will also check for other conditions that may be causing the cysts. You may need to have genetic testing. It can find other problems, such as polycystic kidney disease.
Treatment for simple kidney cysts
Many people with simple kidney cysts don’t need treatment. Your healthcare provider may want to keep track of the cyst over time. You may need ultrasound of the kidneys several times a year.
If you have symptoms, or if the cyst is blocking the flow of urine, you may need treatment such as:
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Over-the-counter pain medicine
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A procedure to puncture the cyst with a long needle inserted through the skin (sclerotherapy)
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Surgery to drain the cyst and remove its outer tissue
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Blood pressure medicine
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Antibiotics and drainage to treat a kidney cyst infection
When to call your healthcare provider
Call your healthcare provider right away if you have any of these: