What is Simple Renal Cyst?
A simple kidney cyst is essentially a small sac filled with fluid that starts from the outer part of your kidney, surrounded by a thin layer. You can have one or even multiple simple cysts growing within your kidneys. It’s important to know that this is the most common type of cyst that can develop in the kidneys.
What Causes Simple Renal Cyst?
Simple renal cysts, which are fluid-filled sacs that develop in the kidneys, are not something a person is born with or inherits from their parents. The exact reason why these cysts form is still a mystery to medical researchers. Some factors seem to increase the risk of developing these cysts, though. For instance, they seem to become more common as individuals get older, particularly after the age of 40. Men also appear to be at more risk than women.
Usually, these kidney cysts are discovered by chance. They’re often found when a person is having an autopsy after they’ve passed away, or during radiological studies – tests that use radiation to produce images of the inside of the body – that were done for other reasons.
Risk Factors and Frequency for Simple Renal Cyst
Simple kidney cysts are very common and become more likely as we age. About 25% of people over the age of 40, and 50% of people over the age of 50, have simple kidney cysts. These cysts can grow to twice their size over a decade. A single kidney cyst is usually found by accident and generally doesn’t cause any symptoms. People with chronic kidney disease who are on dialysis often have multiple kidney cysts.
Signs and Symptoms of Simple Renal Cyst
Simple cysts typically don’t cause symptoms and most people don’t even know they have them. These cysts are often found by accident during an imaging scan done for another reason, like persistent stomach ache. Despite their location in the kidneys, these cysts usually don’t affect how your kidneys work and won’t show up in kidney function tests. However, there are rare instances where simple cysts can cause problems. A cyst could possibly rupture and bleed, become infected, or grow so large that it presses against other organs, causing abdominal pain and discomfort. Although some people with simple cysts have high blood pressure, it’s not been definitively proven that the cysts are the cause.
Testing for Simple Renal Cyst
Kidney cysts, or little fluid-filled sacs in the kidneys, are often discovered unexpectedly during body scans like CT scans or ultrasounds. The ultrasound gives a unique picture of a kidney cyst showing it as a dark, void-like area with thin, barely noticeable walls, and no internal dividing walls or debris.
During a specialized type of body scan, known as a non-contrast, unenhanced CT scan, a kidney cyst can be confirmed with confidence if it shows the following features: the cyst measures as simple fluid (basically appearing like water) of 20 Hounsfield units or less, has no internal dividing walls, does not have any signs of hardening in the central or peripheral area, and has a thin wall. If a contrast-enhanced CT Scan is used (where a special dye, or contrast, is given to the patient to make the scan more detailed), a kidney cyst will be diagnosed if there’s no enhancement (meaning the dye doesn’t cause the cyst to stand out), it measures as simple fluid, has a thin wall, and contains no signs of hardening.
MRI scans, another type of body imaging, also have particular characteristics for identifying a kidney cyst. They appear as areas with uniformly low signal intensity (appearing darker) on T1 weighted images, uniformly high signal intensity (appearing brighter) on T2 weighted images, and don’t show any significant change after IV contrast (a dye similar to what is used in CT scans) is given. If it’s hard to tell whether a cyst is enhancing or not, additional imaging techniques can be used to clarify the diagnosis.
Treatment Options for Simple Renal Cyst
Most cysts don’t require any treatment or further check-ups. However, if a cyst becomes infected, you may need to take antibiotics to clear the infection. If a cyst grows so large that it starts to apply pressure to another organ, it may need to be addressed using one of two common procedures. The first is aspiration and sclerotherapy, in which the cyst fluid is removed and a substance is injected to shrink the cyst. The second is laparoscopic surgery, where a surgeon removes the cyst through small incisions in the abdomen. When using sclerotherapy, ethanol is often the substance of choice.
Without sclerotherapy, just draining the fluid from the cyst (known as aspiration) often results in the cyst coming back, with rates between 20% to 80%. However, simple cysts are typically not treated with surgical exploration, in which a surgeon would make a large incision to openly view the cyst.
What else can Simple Renal Cyst be?
When doctors need to figure out whether a kidney cyst might be cancerous, they often rely on methods outlined by Morton Bosniak in 1986. This approach classifies kidney cysts based on scans, like CT or MRI, and is now a standard way to identify which cysts have a high chance of being cancerous. This could mean they need to be removed or monitored closely.
The Bosniak classification system falls into several categories:
- Bosniak I: These are simple cysts, which are always harmless and do not require further interventions.
- Bosniak II: These are complex cysts, but are also non-cancerous and don’t require further attention.
- Bosniak IIF: These are more complicated cysts that need to be monitored as they can sometimes become cancerous.
- Bosniak III: These cysts need to be treated because there is a 50% to 80% chance they are cancerous.
- Bosniak IV: These cysts are likely to be cancerous, with a more than 90% chance, and need to be treated.
After assessing the type of cyst using this system, the doctors will use these criteria to decide whether surgery or another type of treatment is needed.
Surgical Treatment of Simple Renal Cyst
Doctors no longer use surgery to explore and treat simple kidney cysts.
What to expect with Simple Renal Cyst
Simple cysts, a type of fluid-filled sac that can develop in various parts of the body, do not impact how long you live or cause serious health complications.
Possible Complications When Diagnosed with Simple Renal Cyst
In rare instances, uncomplicated cysts can get infected necessitating treatment with antibiotics.
Likewise, these uncomplicated cysts infrequently grow to a size where they impact other organs and obstruct the flow of urine. In these instances, it becomes crucial to drain the cyst using sclerotherapy or to remove it through minimally invasive surgical procedure known as laparoscopic surgery.
Common Complications:
- Infection requiring antibiotics
- Large cysts causing impact on other organs
- Obstruction of urine flow requiring procedures like sclerotherapy or laparoscopic surgery
