The kidneys and kidney cancer

Most people have two kidneys. They are at the back of the body. One is on each side of the back bone (spine), just underneath the ribcage.

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

On top of each kidney, there is a small gland called the adrenal gland (see illustration below). This makes hormones. 

The kidneys and adrenal glands are surrounded by a layer of fat, contained in a capsule of fibrous tissue (see illustration further down this page).

The kidneys in the body
The kidneys in the body

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How the kidneys work

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 kidney through a large blood vessel called the renal artery. Inside the 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, which are made into urine (pee). The ‘clean’ filtered blood goes back to the rest of the body through the renal vein.

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 two ureters – one from each kidney. 

The ureters connect to the bladder, where urine is stored before being passed out of the body.

The structure of the kidney
The structure of the kidney

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About kidney cancer

Each year, over 12,500 people in the UK are diagnosed with kidney cancer

Kidney cancer usually only affects one kidney. It is very uncommon for cancer to be in both kidneys.

Types of kidney cancer

There are different types of kidney cancer. About 8 out of 10 kidney cancers (80%) are renal cell cancers (RCC). They start in the cortex of the kidney.

There are different types of RCC. The most common type is clear cell renal cancer. 

Less common types are:

  • papillary renal cell cancer
  • chromophobe renal cell cancer.

Kidney cancer can also start in the renal pelvis. This is usually a type of cancer called urothelial cancer or transitional cell carcinoma. We have separate information about the treatment of cancer in the renal pelvis.

Another rare type of kidney cancer is called collecting duct cancer (CDC). This cancer has features of both RCC and of urothelial cancer. 

Your doctor can give you more information about CDC.

Back to Understanding kidney cancer

What is cancer?

There are more than 200 different kinds of cancer, each with its own name and treatment.