Last reviewed January 2013
The kidneys are two bean-shaped organs, each about the size of a fist. They are positioned near the middle of your back, on either side of the backbone (spine).
The kidneys are part of the body’s urinary system. Their main role is to filter blood which removes excess water, salts and waste products. These filtered materials are turned into urine. Urine travels from the kidneys into large funnels called the renal pelvis, through tubes called ureters and into the bladder.
Urine is stored in the bladder until urination, when it leaves the body through a tube called the urethra. In women the urethra is a short tube in front of the vagina. In men the tube is longer and passes through the prostate and penis.
The small units of the kidney that filter blood are called nephrons. Each kidney has about one million nephrons. Nephrons regulate blood pressure and volume, the blood’s acid-base balance (pH), and the levels of chemical substances, such as electrolytes.
The kidneys also produce hormones which trigger the production of red blood cells and control the body’s calcium levels.
An adrenal gland, which produces hormones, sits above each kidney. Although adrenal glands are not part of the urinary system cancer can spread to them.
The urinary tract is lined with tissue called the urothelium, which is made up of urothelial cells.
In the early stages of kidney cancer the primary cancer forms a tumour that is confined to the kidney. As the cancer grows it may invade organs or structures near the kidney such as the adrenal glands, ureters or liver. It may also spread to other parts of the body such as the lungs or bones. Sometimes cancers in the kidney can be a secondary cancer (metastasis) from a primary cancer located in another part of the body.
About 90 per cent of all kidney cancers are renal cell carcinoma (RCC). RCC starts in the kidney’s nephrons. Usually only one kidney is affected but in rare cases both can be affected.
The most common type of RCC is called clear cell carcinoma, based on the way the cells look under the microscope. Other more rare RCCs include papillary, chromophobic, oncocytic and sarcomatoid kidney cancers.
Urothelial carcinoma (or transitional cell carcinoma) is a rare type of kidney cancer that can begin in the renal pelvis where the kidney and ureter meet. It can also occur in the ureter where it would be treated as cancer of the ureters or ureteral carcinoma.
Other rare types of kidney cancer are renal sarcoma which affects the kidney’s connective tissue; renal lymphoma which starts in the kidney’s lymphatic tissue; and Wilms’ tumour which is more common in children than adults.
This page provides information on renal cell carcinomas. For information about other types of kidney cancer call Cancer Council 13 11 20.
The exact causes of kidney cancer are not known. However several factors are known to increase the risk of developing kidney cancer:
Smoking—people who smoke have almost twice the risk of developing kidney cancer as non-smokers. Up to one-third of all kidney cancers are thought to be related to smoking.
Heavy use of certain medications—these include diuretics and pain-killers with the ingredient phenacetin. Phenacetin is no longer used but people who took pain relievers with phenacetin (most likely before 1970) may be at a higher risk.
Exposure to certain substances—people with regular exposure to certain chemicals such as asbestos, cadmium, lead, herbicides or organic solvents, may have an increased risk.
Family history—people who have family members with kidney cancer, especially a sibling, are at increased risk. Having an inherited condition such as von Hippel-Lindau disease or Birt-Hogg-Dubé syndrome also increases the risk.
Obesity—excess body fat may cause changes in certain hormones that can lead to kidney cancer.
High blood pressure—this is often a risk factor in people who are overweight. However other medical conditions can also cause high blood pressure.
Kidney disease—people with advanced kidney disease have a higher risk of developing kidney cancer.
Most people with kidney cancer have no symptoms and are diagnosed with the disease when they see the doctor for another reason. Symptoms can, however, include:
- blood in the urine (haematuria)
- a change in urine colour to a dark or rusty brown
- pain in the lower back on one side not due to an injury
- pain or a lump in the abdomen or side (flank)
- constant tiredness
- unexplained weight loss
- fever (not caused by a cold or flu)
- swelling of the abdomen or extremities e.g. ankles, feet.
You may also have a low red blood cell count (anaemia) or a high red blood cell count (polycythaemia). These conditions can cause fatigue and dizziness, among other symptoms.
If you have any of the above symptoms it’s important to have them checked by your doctor but remember they are common with many other conditions and most people with these symptoms will not have cancer.
Information reviewed by: A/Prof Manish Patel, Urological Cancer Surgeon, University of Sydney and Westmead and Macquarie University Hospitals, NSW; Annie Angle, Cancer Nurse, Cancer Council VIC; Lyn Bland, Consumer; Gregory Bock, Cancer Nurse Coordinator (Urology), WA Cancer and Palliative Care Network; Prof Ian Davis, Professor of Medicine and Head of Eastern Health Clinical School, Faculty of Medicine and Nursing and Health Science, Monash University and Senior Medical Oncologist, Eastern Health, VIC; Karen Hall, Clinical Nurse, Cancer Services Division, Flinders Medical Centre and Nurse Health Counsellor, Cancer Council SA; and Frank Hughes, Helpline – Cancer Information and Support, Cancer Council QLD.