Kidney cysts are round pouches of fluid on or within the kidneys. Up to half of all people over the age of 50 have one or more cysts on their kidneys, and most won't experience symptoms or health problems as a result of these "simple cysts." They may only be discovered incidentally when a person undergoes imaging for another reason. Some people with kidney cysts have a condition called polycystic kidney disease, which causes multiple cysts on the kidneys. Individuals with polycystic kidney disease can develop high blood pressure or kidney problems, and some will progress to kidney failure. However, most kidney cysts are non-cancerous and do not have a tendency to become malignant.
Scientists and medical professionals are working to better understand the causes of kidney cysts. One theory suggests the culprit could be a weak spot on the kidney. A pouch forms and fills with fluid (a diverticulum), then detaches as a cyst. Kidney cysts become more common with age.
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Obstruction of the tubules may also cause kidney cysts. The tubules facilitate the collection of urine, so when kidney cysts affect them, the individual may experience other symptoms. Cysts sometimes block the flow of urine out of the kidney, become infected, or rupture.
Polycystic kidney disease (PKD) is a genetic disorder that runs in families. Cysts associated with the condition are nearly always noncancerous. Some people go their whole lives without knowing they have PKD unless complications arise. Like other kidney cysts, these growths are small, oval or round sacs filled with fluid. Cysts due to PKD are more likely to cause problems than simple cysts are. If the condition does cause problems, individuals can experience high blood pressure, liver cysts, weakened blood vessels in the brain, or kidney failure.
Medullary cystic kidney disease (MCKD) is an inherited condition that results in cyst formation within the inner part of the kidney, the medulla. The condition often leads to scarring of the kidneys and may progress to kidney failure. The symptoms of MCKD most often manifest when people are between the ages of 20 and 50.
In the case of medullary sponge kidney, cysts develop in the urine-collecting ducts and tubules of one or both kidneys. It's a congenital disorder, meaning the cysts are present at birth. While experts suspect the condition is hereditary, the exact cause is not known. People with a family history of medullary sponge kidney should consult with a doctor for testing and diagnosis.
Age seems to be a primary factor in the development of kidney cysts. Men are at higher risk, but nearly half of people 50 or older will have one or more simple cysts. If the sac does not go away on its own or is not removed, the cyst may expand over time. A cyst can double in size in ten years.
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Simple kidney cysts do not often cause drastic symptoms and typically do not require treatment. However, they can grow big enough to cause dull pain in the side, back, or upper abdomen. Kidney cysts that become infected or tender can cause fever and pain. They can even burst, though this complication does not generally significantly impair kidney function.
There are many possible causes of kidney cysts and there's no sure way to prevent them. The best approach is to practice good renal health, which includes drinking lots of water and ensuring sodium intake remains within the recommended daily amount. Anyone who thinks they may have a cyst should speak to a doctor and get a diagnosis.
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