The kidneys are a pair of bean-shaped, fist-sized organs below the rib cage in the back of the abdomen. One sits on each side of the spine. They filter waste products, excess water, and salt from the blood. These organs regulate the body's balance of fluids and minerals such as potassium and sodium. They also produce hormones that monitor blood pressure and regulate the production of red blood cells.
Patients whose kidneys have failed or don't work well generally need dialysis or a kidney transplant. During dialysis, a machine takes on the job of filtering waste products from the blood.
Kidney cancer occurs when abnormal kidney cells grow and divide uncontrollably. The cells invade and destroy the normal kidney tissue, and they can spread (metastasize) to other organs. Even if a person has kidney cancer, their kidneys may still function normally.
In addition to tissues that provide filtering functions, the kidneys also have a central portion that collects the filtered urine before it is transported to the bladder for excretion. Each of these two areas contains different types of cells and each can give rise to specific types of cancers.
The filtering parts of the kidneys can develop renal cell carcinoma, which has several sub-types. The most common types of renal cell carcinoma are clear cell cancer, papillary cell cancer, and chromophobe renal cell cancer. The cancerous parts of the kidneys that collect and transport urine are known as transitional cell carcinoma.
Renal cell carcinoma accounts for most kidney cancers. It begins in the lining of the small tubes that make up the kidney. Although renal cell carcinoma typically develops as a single tumor in one kidney, it sometimes affects more than one part of a kidney or even both kidneys. It has been linked to smoking and exposure to cadmium.
Certain genetic abnormalities can cause renal cell carcinoma or make people more likely to develop it. In these cases, the cancer generally starts at an early age and may affect both kidneys. For example, people with von Hippel-Lindau disease are prone to developing kidney cancer. Several other types of genetic abnormalities also exist. If present, may require family members to be screened for kidney cancer even if they show no symptoms.
Transitional cell carcinoma accounts for only a small percentage of kidney cancers. It usually begins in the renal pelvis. This funnel-shaped structure, which connects the ureter to the main part of the kidney, drains urine from the kidney. Transitional cell carcinoma can also affect the ureters, which carry urine from the kidneys to the bladder, and the bladder lining. Studies suggest that this type of cancer is also linked to smoking. The pain reliever phenacetin may also be associated with an increased risk of kidney cancer.
Most kidney cancers in children develop before age 5. They are commonly called Wilms' tumors.
Your risk of kidney cancer is higher if kidney cancer runs in your family or if you
- are obese
- have had prolonged exposure to asbestos, cadmium, or petroleum products
- have family members who have had kidney cancer
- have had long-term dialysis treatment
- have tuberous sclerosis, a disease characterized by bumps on the skin caused by small tumors in blood vessels
- have von Hippel-Lindau disease, a rare genetic disorder that causes tumors to grow in various parts of the body.
Most kidney cancers grow without causing any pain or discomfort. Some are discovered before they begin to cause symptoms, such as when a person has a CT scan of the abdomen for another reason.
Renal cell carcinoma can cause a variety of symptoms that seem unrelated to the kidney. For example, it can spread into nearby veins, causing congestion or blockages within the veins. The tumor can also make too much of one or more hormones. Symptoms can result from the tumor itself, from vein blockage, or from the effect of hormones.
Some symptoms of kidney cancer include
- blood in the urine
- abdominal pain
- a lump in the abdomen
- weight loss
- unexplained fever
- enlarged lymph nodes
- enlarged veins in the scrotum (in males)
- high blood pressure that is not easily controlled
- trouble breathing or leg pain (due to blood clots)
- a swollen abdomen (due to excess fluid)
- bones that break easily.
Because a person with kidney cancer may not have any symptoms, the disease may be identified by accident. For example, imaging studies taken to evaluate a different health problem may show a kidney tumor. More often, kidney cancer is found after a patient reports symptoms to a doctor and then has tests to determine what's wrong.
Incidental discovery of kidney tumors has become more common with the increased use of ultrasound, CT scans and MRIs. Depending upon the size of the tumor, it may not require any immediate specific treatments other than close monitoring. If it begins to grow, treatment can be initiated.
Abnormal laboratory tests, such as blood and urine tests, can be the first clue that someone has kidney cancer. Some abnormal findings are caused by the cancer's hormonal or chemical effects on the body. Abnormal findings might include
- anemia (a low number of red blood cells)
- a high number of red blood cells
- abnormal calcium level in the blood
- abnormal kidney function
- blood in the urine
- Your doctor may also feel a mass on one side of your abdomen.
If your doctor suspects kidney cancer, he or she probably will order a computed tomography (CT) scan. In a CT scan, a modified x-ray beam produces body images at different angles, offering a look at the inside of the kidneys and other organs.
Your doctor may also order an ultrasound or magnetic resonance imaging (MRI) to help diagnose kidney cancer. Ultrasound uses sound waves to create pictures of the kidney. It can help determine whether a kidney mass is a noncancerous (benign) fluid-filled cyst or a cancerous tumor. MRI uses large magnets and radio waves to create images of the kidneys and nearby organs on a computer.
In the past, doctors commonly used a test called intravenous pyelography (IVP) to diagnose kidney cancer. (IVP is an x-ray–based imaging study that uses contrast dye to look at the urinary system.) But CT and MRI scans have largely replaced IVP.
Other tests may be done at the same time or after the diagnosis has been made to see if the cancer has spread. These tests may include
- MRI and an MRI urogram. Images made during this test can show whether the cancer has spread to blood vessels in the abdomen.
- Chest x-ray and CT scan of the lungs. Your doctor may order these tests to determine whether kidney cancer has spread to the lungs or chest bones.
- Bone scan. This test uses small, safe levels of radioactive material show whether cancer has spread to your bones.
Small tumors may be seen in people that have a CT scan for an unrelated reason. It's quite common. When they are less than an inch in diameter, doctors will sometimes monitor such findings and not necessarily subject the patient to immediate surgery. These tumors could be benign. Or even if they are malignant, they might grow very slowly and never cause a problem.
Most kidney cancers will continue to grow and spread until they are treated. If the cancer can be removed with surgery, cure is possible. Non-surgical treatments may slow the cancer's growth but don't eliminate the tumor.
Many small kidney cancers are detected by accident, so they may be watched over time. Treatment can start if the tumor grows.
Because about one-third of renal cell carcinomas are linked to smoking, you may reduce your kidney cancer risk by avoiding tobacco. At work, avoid exposure to asbestos and cadmium.
To identify early kidney cancer in dialysis patients, doctors suggest periodic kidney x-rays. This is especially important if the patient has cysts in the kidneys.
Treatment is determined by the type of cancer and how far it has spread (its stage). Your age, general health, and personal preferences may also affect your treatment choice. The main treatments for kidney cancer are surgery, biological therapy, and radiation therapy.
Patients with very small kidney cancers may opt to wait on treatment. Repeat scans are performed periodically. Surgery can be performed or other therapy started if the tumor begins to grow. This approach is more common in elderly or frail patients.
Surgery is the most important treatment for kidney cancer; the chances of surviving without it are poor. However, it only cures the disease if the entire tumor is removed. The chances of a cure go down if the disease has spread.
Even if the cancer has spread, surgery can still help. If a surgeon removes most of the tumor, your immune system and medical treatments will have less cancer to fight.
The amount of tissue your surgeon removes will depend on the stage and type of kidney cancer. During a radical nephrectomy, the surgeon removes the entire kidney. In the past, he or she also removed the nearby adrenal gland, lymph nodes and fatty tissue. Today, however, the lymph nodes are generally not removed unless they are enlarged. The adrenal gland is often left as well, unless it is directly involved by the tumor.
During a partial nephrectomy, the surgeon only removes the part of the kidney that contains the tumor. With this operation, there is a risk that some cancer cells may be left behind.
Depending on the cancer, your surgeon may use a camera-guided procedure known as laparoscopy. (It may also be called minimally invasive surgery.) During this type of operation, the surgeon can remove part, or all, of the kidney through much smaller incisions.
Another potential option may be robotic surgery, which also can be performed through smaller incisions. The traditional surgical incision is quite large, and recovery generally takes eight to 12 weeks. With minimally invasive techniques, your recovery time is much shorter.
A procedure called arterial embolization shrinks the tumor. Your doctor may do this before your operation to make surgery easier. Or, if surgery is not possible, arterial embolization can ease symptoms.
During an arterial embolization, the doctor inserts a small tube (catheter) into an artery in the groin. The tube is moved through the vessel until it reaches the artery that feeds the kidney. A substance is then injected into the artery to block it. This helps keep the tumor from growing.
Other ways of treating the cancer without actually removing it include:
- Radiofrequency ablation -- heat waves directed at the tumor kill the cancer cells
- Freezing therapy
- Very focused radiation known as cyber knife or surgical gamma knife
When kidney cancer has spread to distant sites, the sites are called metastases. Removing metastases can relieve pain and other symptoms for a while, but it does not prolong survival.
A major advance in cancer management has been the introduction of targeted therapies. The growth and spread of kidney cancers are controlled by specific chemical reactions inside the cancer cells and, less often, in normal cells. Drugs called targeted therapies can limit or block these chemical reactions. Additional new effective therapies continue to be discovered.
Prior to the introduction of targeted therapies, the most common treatment for advanced kidney cancer was biological therapy (immunotherapy). It helps the body's immune system fight and destroy cancer cells. There are a few types of biological therapy. These include proteins called cytokines that activate the immune system. There is also a "vaccine" that promotes cytokine production within cancer cells.
Agents called angiogenesis inhibitors can treat renal cell carcinoma. By preventing the growth of blood vessels to "feed" the tumor, these agents slow the cancer's growth. However, they are currently considered experimental.
Radiation therapy relies on high-energy radiation to kill cancer cells. Sophisticated, highly focused beams of radiation can target the cancer while sparing surrounding healthy tissues. This therapy can be used with other treatments to lessen symptoms and in patients who are too ill to undergo surgery.
Traditional chemotherapy is often not used to treat kidney cancer because few patients benefit. Targeted therapies and angiogenesis inhibitors are quite effective and cause fewer side effects than chemotherapy.
When To Call a Professional
Contact your doctor if you
- see blood in your urine
- notice a lump or swelling in your abdomen
- have abdominal pain that doesn't go away
- lose weight for no reason
- feel very fatigued.
- If you have undergone a CT scan or MRI for some unrelated reason and a small tumor is incidentally found on the kidney, specialty consultation will be needed to help determine watchful waiting with close follow-up or immediate treatment.
If kidney cancer is diagnosed early, before it breaks through the kidney, it may be cured with surgery. This is the case for about half of all patients with kidney cancer. If the cancer is removed and the surrounding area is free of cancer cells, most patients will survive for at least five years. The survival rate drops significantly in people whose cancer has spread to the lymph nodes, circulatory system, and distant organs.