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The kidneys

The kidneys are two bean-shaped organs, each about the size of a fist. They are deep inside your abdomen, positioned near the middle of your back, on either side of the spine. The kidneys are part of the body’s urinary system.

What the kidneys do

The main role of the kidneys is to filter and clean the blood. Blood flows into each kidney through the renal artery and is filtered through tiny networks of tubes called nephrons. The clean blood then goes back into the rest of the body through the renal vein.

When the kidneys filter the blood, they remove excess water and waste products and turn these into urine (wee or pee). Urine travels from each kidney into a funnel called the renal pelvis, then through a long, thin tube called the ureter, and into the bladder.

Urine is stored in the bladder until you need to urinate, when it leaves the body through a tube called the urethra. In females, the urethra is a short tube in front of the vagina. In males, the tube is longer and passes through the prostate and penis.

Hormone production – The kidneys also help your body control how much blood it needs. They do this by making hormones that regulate blood pressure and trigger the production of red blood cells.

Adrenal glands – An adrenal gland sits above each kidney. The adrenal glands produce a number of hormones. Although these glands are not part of the urinary system, kidney cancer can sometimes spread to them.

This information is reviewed by

This information was last reviewed November 2020 by the following expert content reviewers: A/Prof Daniel Moon, Urologic Surgeon, Australian Urology Associates, and Honorary Clinical Associate Professor, The University of Melbourne, VIC; Polly Baldwin, 13 11 20 Consultant, Cancer Council SA; Ian Basey, Consumer; Gregory Bock, Urology Cancer Nurse Coordinator, WA Cancer and Palliative Care Network, North Metropolitan Health Service, WA; Tina Forshaw, Advanced Practice Nurse Urology, Canberra Health Services, ACT; Dr Suki Gill, Radiation Oncologist, Sir Charles Gairdner Hospital, WA; Karen Walsh, Nurse Practitioner, Urology Services, St Vincents Private Hospital Northside, QLD; Dr Alison Zhang, Medical Oncologist, Chris O’Brien Lifehouse and Macquarie University Hospital, NSW.