A fluid-filled swelling within the cortex, the outer part of the kidney
- More common over the age of 50
- Gender, genetics, and lifestyle are not significant factors
Kidney cysts form in the cortex (outer layer) of the kidney. They often occur singly, but three or four may develop. Kidney cysts are very common; up to half of all people over the age of 50 have at least one cyst, often without realizing it. The cause is not known.
Unlike the multiple cysts that occur in polycystic kidney disease, kidney cysts do not affect kidney function and are usually harmless. In most cases, they cause no symptoms. Rarely, a kidney cyst may become large enough to cause back pain, or it may bleed, causing blood to appear in the urine.
What might be done?
A kidney cyst is often detected by chance during ultrasound scanning, CT scanning, or intravenous urography performed to investigate another condition. Rarely, a fluid sample may need to be taken from the cyst through a hollow needle to be examined for cancerous cells. This procedure is carried out under local anaesthesia using ultrasound to locate the cyst.
A simple kidney cyst does not require treatment unless symptoms develop. However, if the cyst becomes painful, you may be sent to hospital to have fluid removed from it using a needle and syringe. Alternatively, the cyst can be removed surgically.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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