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Simple kidney cysts are fluid-filled sacs that form in your kidneys. These cysts usually don’t affect how the kidneys function. The kidneys are 2 bean-shaped organs located near the middle of your back. They filter large amounts of blood each day. They also help regulate the fluid and salts (electrolytes) in your blood. They release waste products through your urine.
Simple kidney cysts are very common. They rarely need treatment. Most people don’t even know that they have them. 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. Most commonly, you’ll have only a single cyst. Over time, the cyst might slowly increase in size.
Simple kidney cysts become more common with age. But sometimes they are present at birth. Men get these cysts more often than women do. As medical imaging becomes more frequent, more and more people are diagnosed with these cysts.
Simple kidney cysts are different from complex kidney cysts. Healthcare providers can identify the type of cyst based on its appearance with medical imaging. Simple kidney cysts are the most common type. These cysts have thin walls and a regular, rounded shape. They are filled only with fluid. In contrast, a complex kidney cyst might have thicker walls and an irregular shape. It might also contain solid material. A complex kidney cyst might be a sign of cancer. But simple kidney cysts are not cancerous and never will become so.
Researchers are still not sure what causes simple kidney cysts. 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.
Some medical conditions can cause kidney cysts to grow. For example, a person with polycystic kidney disease develops a large number of kidney cysts. (The cysts may be simple or complex.) Too many cysts can prevent the kidney from working properly.
Other medical conditions that can cause simple or complex kidney cysts include:
If you smoke or have high blood pressure, you might have an increased risk of getting a simple kidney cyst. It’s not clear whether stopping smoking or controlling your blood pressure might reduce this risk.
Most people don’t notice any symptoms from their simple kidney cysts. Rarely, they might cause:
These cysts usually don’t majorly impair kidney function unless they block the ureter. More commonly, some cysts might cause a slight drop in kidney function. But that doesn’t tend to cause any medical problems or symptoms.
For most people who have both simple kidney cysts and high blood pressure, the cysts are not the cause of the high blood pressure.
Simple kidney cysts are often first found with an imaging test that was done for another reason. Your healthcare provider will perform a medical history. He or she will ask about your recent symptoms and past medical problems. You’ll also need a physical exam.
It is important to distinguish simple kidney cysts from complex cysts. Complex cysts might be cancerous. They usually need to be removed. For this reason, your healthcare provider might order medical imaging tests like:
A radiologist will look at these images to see if your kidney cyst is simple or complex. Healthcare providers sometimes rate cysts with the Bosniak CT system. It places cysts into 5 categories, which are I, II, II-F, III, and IV. The categories are based on complexity and possible malignancy. If your cyst is ranked a category I cyst, you probably won’t need any more imaging. Kidney cysts with higher ratings might need more imaging or treatment. Category IV cysts are most often linked with cancer.
Your healthcare provider will also check for other conditions that may be causing the cysts. If the diagnosis is still unclear after medical imaging, you might need to have genetic testing. It can help rule out other conditions, such as polycystic kidney disease.
Many people with simple kidney cysts don’t need treatment. Healthcare providers may want to closely watch the cysts. You may need occasional ultrasounds of the kidneys.
If you have symptoms, or if the cyst is blocking the flow of urine, you might need one of the following treatments:
Call your healthcare provider right away if you start having possible symptoms from your kidney cyst. These may include blood in your urine, pain in your back, or problems passing urine.
Simple kidney cysts are fluid-filled sacs that form in your kidneys. Though abnormal, these cysts usually don’t affect how your kidneys work.
Tips to help you get the most from a visit to your healthcare provider:
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