The kidneys and ureters

The kidneys are part of the urinary system. They filter the blood to remove excess water and waste products.

About the kidneys

Most people have 2 kidneys. They sit in the tummy (abdomen), towards the back of the body. There is one on each side of the backbone (spine), just underneath the back of the ribcage.

The kidneys are part of the urinary system. They filter the blood to remove excess water and waste products. These are then made into pee (urine).

On top of each kidney, there is a small gland called the adrenal gland. This makes hormones. The kidneys and adrenal glands are surrounded by a layer of fat. They are contained in a capsule of fibrous tissue.


The kidneys in the body
Image: The kidneys in the body


What do the kidneys do?

The kidneys clean the blood and keep anything the body needs. This helps control the balance of fluid, salt and minerals in the body. It also helps maintain blood pressure.

Blood goes to the kidneys through large blood vessels called the renal arteries. Inside each kidney, there are millions of tiny filters called nephrons. The nephrons start in the part of the kidney called the cortex and extend into triangle-shaped areas called renal pyramids.

The nephrons filter the blood to remove waste products and any extra water. These are made into urine. The filtered blood goes back to the rest of the body through the renal veins.

Related pages

The ureters and renal pelvis

The urine collects in an area in the middle of each kidney. This area is called the renal pelvis. Urine then drains from each kidney through a long, muscular tube called a ureter. There are 2 ureters – one from each kidney. 

The ureters connect to the bladder. The bladder is where urine is stored before it passes out of the body through another tube called the urethra.

Lymph nodes are part of the lymphatic system. The lymphatic system helps to protect us from infection and disease.


The structure of the kidney
Image: The structure of the kidney


About our information

  • References

    Below is a sample of the sources used in our kidney cancer information. If you would like more information about the sources we use, please contact us at

    Escudier B, et al. Renal cell carcinoma: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Annals of Oncology 30: 706-720, 2019. doi:10.1093/annonc/mdz056 Published online 21 February 2019. Available from (accessed April 2021).

    European Association of Urology. Renal cell carcinoma guidelines. EAU Guidelines. Edn. presented at the EAU Annual Congress Milan 2021. ISBN 978-94-92671-13-4. Available from (accessed April 2021).

    National Institute for Health and Care Excellence (NICE): Nivolumab with ipilimumab for untreated advanced renal cell carcinoma. Technology appraisal guidance (TA581). Published 15 May 2019. Available from (accessed April 2021).

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr Lisa Pickering, Consultant Medical Oncologist.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

Date reviewed

Reviewed: 01 November 2021
Next review: 01 November 2024
Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

Our cancer information meets the PIF TICK quality mark.

This means it is easy to use, up-to-date and based on the latest evidence. Learn more about how we produce our information.