Most people have two kidneys. They sit at the back of the body, one on each side, just underneath the ribcage. The kidneys filter the blood and remove waste products, which they convert into urine. Urine drains from each kidney, through a tube called a ureter, to the bladder where it is stored. When you’re ready to pass urine it leaves the body through another tube called the urethra.
Blood is carried to the kidney through a blood vessel called the renal artery. Renal means ‘to do with the kidney’. After the blood has been filtered by thousands of tiny filters called nephrons, it travels back to the rest of the body through the renal vein.
The kidneys also help to control the balance of fluid, salt and minerals in the body and to maintain blood pressure.
The kidneys are contained in a fibrous covering called the Gerota’s fascia and surrounded by a layer of fat. The outer part of the kidney that makes urine is called the cortex. The inner part that collects urine is called the medulla.
On top of each kidney sits a small gland called the adrenal gland, which produces important hormones.
Types of kidney cancer
Kidney cancer affects more men than women. Kidney cancer is more common in people over 60 and rarely affects people under 40. Usually only one kidney is affected, and it’s rare for cancer to affect the other kidney. Cancer of the kidney isn’t infectious and can’t be passed on to other people.
Wilms’ tumor (or nephroblastoma) is an uncommon type of kidney cancer that can affect very young children.
There are different types of kidney cancer. About 90% of kidney cancers (9 out of 10) are renal cell cancers (RCC), sometimes called renal adenocarcinoma. They start in the cells that line very small tubes, called tubules, in the kidney cortex. There are different types of renal cell cancer. The most common type is clear cell renal cancer. Less common types are papillary, chromophobe and collecting duct renal cancer. Another type of cancer that can affect the kidneys starts in the cells that line the renal pelvis, where the kidney joins with the ureter. These cancers, sometimes called transitional cell cancers, behave and are treated differently to renal cell cancer.
This section is about renal cell cancer, which we call kidney cancer. You can talk to our cancer support specialists to find out more about the rarer types of kidney cancer.
Risk factors and causes of kidney cancer
The causes of kidney cancer are unknown, but research is going on to try to find out more. There are certain things that can affect the chances of developing kidney cancer. These are called risk factors. Having a risk factor doesn’t necessarily mean you’ll get kidney cancer.
The risk of kidney cancer increases with age and most cases happen in people over 60.
The longer a person smokes and the more tobacco they smoke, the greater their risk of developing kidney cancer. Risk goes down when a person stops smoking.
Studies show that people who are overweight have an increased risk of developing kidney cancer.
Some medical conditions, such as high blood pressure (hypertension), may increase the risk of kidney cancer. People with advanced kidney disease, especially those who need treatment to replace what a kidney does (dialysis), have a higher risk of developing kidney cancer.
Most kidney cancers aren’t inherited. However, people who have one or more first degree relatives (parent, brother, sister or child) with kidney cancer may have a higher than average risk of getting kidney cancer.
Some rare genetic conditions where people have an inherited faulty gene can increase the risk of developing kidney cancer. These include von Hippel-Lindau disease, hereditary papillary renal cell carcinoma (HPRCC) and Birt-Hogg-Dube (BHD) syndrome. Kidney cancers that happen because of an inherited faulty gene are more likely to cause several tumors, affect both kidneys and happen at a younger age.
Exposure to certain materials at work
Exposure to certain materials at work, such as cadmium, lead or asbestos, may affect a person’s risk. An increased risk of kidney cancer has been linked to working with blast furnaces or coke ovens in the steel and coal industries. It has also been linked to working with Trichloroethylene (Tric), a petroleum by-product used in the heavy engineering industry.