What is kidney cancer?

Kidney cancer is when abnormal cells in either of the kidneys start to divide and grow in an uncontrolled way. The cells can grow into surrounding tissues or organs and may spread to other areas of the body.

The kidneys and urinary system

Kidneys are part of your urinary system. This system filters waste products out of the blood and makes urine. It includes:

• 2 kidneys

• 2 ureters

• bladder

• prostate (in men)

• urethra

What are the kidneys?

The kidneys are two bean shaped organs, each about the size of a fist. They are near the middle of your back, one on either side of your spine.

How do the kidneys work?

Inside the kidney tiny networks of tubes called nephrons filter the blood. As blood passes through the nephrons extra water and waste are taken away. Any substances that your body needs are returned to the bloodstream.

Inside the nephrons waste products move from the small blood vessels into urine collecting tubes. The urine gathers in an area called the renal pelvis at the centre of each kidney. From here it drains down a tube called the ureter and into the bladder.

There are 2 ureters, one from each kidney. Another tube called the urethra carries the urine from the bladder out of your body when you need to pee.

Blood supply

The kidneys have a very rich blood supply. Blood passes through in large amounts so the kidneys can filter it to remove waste products.

The large blood vessels carrying waste products to the kidneys are called the renal arteries. There are also large blood vessels carrying the cleaned blood away. These are called the renal veins. 

Hormones

The kidneys also produce 3 important hormones:

• erythropoietin (EPO), which tells your bone marrow to make red blood cells
• renin, which regulates blood pressure
• calcitriol (a form of vitamin D), which helps the intestine absorb calcium to keep your bones healthy

Adrenal glands

Above each kidney is an adrenal gland. These small glands make important hormones:

• cortisol, a natural steroid hormone
• aldosterone, which helps to regulate the body’s water balance
• adrenaline, a hormone released when you are stressed
• noradrenaline, an adrenaline-like hormone

Where does kidney cancer start?

The kidneys are made up of different types of cells. The type of cancer you have depends on the type of cell the cancer started in.

The most common type of kidney cancer is renal cell cancer (RCC). It starts in the cells lining the tubules (the smallest tubes) inside the nephrons.

The main type of renal cell cancer is clear cell cancer. Other types include:

• papillary cell cancer
• chromophobe cell cancer

Who gets kidney cancer?

Kidney cancer is more common in older people. It's diagnosed more often in men than women.

Factors that increase your risk of kidney cancer include: 

• smoking
• being overweight or obese

How common is kidney cancer?

Around 11,900 people are diagnosed with kidney cancer in the UK each year.