What are the kidneys?

Kidneys are bean-shaped organs located in the lower back. The kidneys help to control the amount of salt and water in the body, and also remove waste products by filtering the blood and making urine.

Inside the kidneys are small working parts called nephrons. Each nephron is made up of a filter and a tube. As blood flows through the kidneys to be filtered, the nephrons remove extra water and waste products, which leave the body as urine.

What are simple kidney cysts?

A cyst is a closed pouch or sac filled with air or liquid. Simple kidney cysts are usually small round sacs that have a thin wall and are filled with a watery fluid. As people get older, cysts can form on the surface or in the nephrons of the kidneys. They can range in size from a small pea to as large as a grapefruit. Cysts can also grow over time.

Who gets simple kidney cysts?

Simple kidney cysts are very common as people begin to age; up to half of all people 50 years of age and older have at least 1 kidney cyst. Most people have a cyst in only 1 kidney, but the number of cysts and the risk of getting cysts in the second kidney increase as we get older.

Are simple kidney cysts dangerous?

Simple kidney cysts are almost always harmless. They are called "simple" because there is very little chance they will develop into something more serious. However, some cysts do have thickened walls, may look irregular on X-rays, and could be associated with kidney cancers.

What causes simple kidney cysts?

Kidney cysts occur when the tube of a nephron begins to get bigger and fill with fluid. Researchers do not know what causes this to occur, but they do know that simple cysts are not inherited. It is believed that injury or microscopic blockages in the tubules may lead to the development of some simple kidney cysts.

What are the symptoms of simple kidney cysts?

Simple kidney cysts usually don't cause any symptoms. In fact, most people who have them don't know they have them. The cysts become a problem if they rupture (break open) and start to bleed, become infected, or grow so large that they push against other organs within the abdomen.

When simple kidney cysts do cause symptoms, they might include:

Depending on where the cyst is located, it can affect how the kidney works. It can also lead to a type of high blood pressure if the cyst prevents the kidney from filtering extra fluid from the blood.

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