What is kidney cancer?

Kidney cancer develops 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 kidney 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 same size as 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 all unwanted waste is taken away. Chemicals that your body needs are kept or 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 the body.

Blood supply

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

The main blood vessel to the kidney is called the renal artery. There are also large blood vessels carrying the cleaned blood away. These are called the renal veins. 

Hormones

The kidneys also produce three 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:

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

If you have a kidney removed, you may have the adrenal gland above it removed too. This happens if your surgeon thinks it may contain cancer cells. It's quite unusual for cancer to spread to one of the adrenal glands. 

The adrenal hormones are important. But if you have an adrenal gland removed you will be perfectly well with only one. The remaining adrenal gland will make all the hormones you need. It's unusual to have both adrenal glands removed. You would need to take hormone tablets every day if this happens.

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 starts in.

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

The main types of renal cell cancer are:

• clear cell - around 75 out of 100 renal cell cancers (75%)
• papillary - around 15 in 100 renal cell cancers (15%)
• chromophobe - around 5 in 100 renal cell cancers (5%)

Who gets kidney cancer?

Kidney cancer is more common in older people.

It's diagnosed more often in men than women. This could be because in the past more men smoked cigarettes. Smoking increases your risk of getting kidney cancer.

How common is kidney cancer?

Around 13,300 kidney cancers are diagnosed in the UK each year.

Kidney cancer is the 7th most common cancer in the UK.