How Is Kidney Cancer Diagnosed?
Kidney cancer might be found because of signs or symptoms a person is having, or it might be found because of lab tests or imaging tests a person is getting for another reason. If cancer is suspected, tests will be needed to confirm the diagnosis.
Medical history and physical exam
If you have any signs or symptoms that suggest you might have kidney cancer, your doctor will want to take a complete medical history to check for risk factors and to learn more about your symptoms.
A physical exam can provide information about signs of kidney cancer and other health problems. For example, the doctor may be able to feel an abnormal mass when he or she examines your abdomen.
If symptoms or the results of the physical exam suggest you might have kidney cancer, more tests will probably be done. These might include lab tests and imaging tests.
Lab tests cannot show for sure if a person has kidney cancer, but they can sometimes give the first hint that there may be a kidney problem. If cancer has already been diagnosed, they are also done to get a sense of a person’s overall health and to help tell if the cancer might have spread to other areas. They also can help show if a person is healthy enough to have an operation.
Urinalysis (urine testing) is sometimes part of a complete physical exam, but it may not be done as a part of more routine physicals. This test may be done if your doctor suspects a kidney problem.
Microscopic and chemical tests are done on a urine sample to look for small amounts of blood and other substances not seen with the naked eye. About half of all patients with renal cell cancer will have blood in their urine. If the patient has transitional cell carcinoma (in the renal pelvis, the ureter, or the bladder), sometimes a special microscopic exam of the urine sample (called urine cytology) will show actual cancer cells in the urine.
Complete blood count
The complete blood count (CBC) is a test that measures the amounts of different cells in the blood, such as red blood cells, white blood cells, and platelets. This test result is often abnormal in people with renal cell cancer. Anemia (having too few red blood cells) is very common. Less often, a person may have too many red blood cells (called polycythemia) because the kidney cancer cells make a hormone (erythropoietin) that causes the bone marrow to make more red blood cells.
Blood counts are also important to make sure a person is healthy enough for surgery.
Blood chemistry tests
Blood chemistry tests are usually done in people who might have kidney cancer, because the cancer can affect the levels of certain chemicals in the blood. For example, high levels of liver enzymes are sometimes found. High blood calcium levels may indicate that cancer has spread to the bones, and may therefore prompt a doctor to order a bone scan. Blood chemistry tests also look at kidney function, which is especially important if certain imaging tests or if surgery is planned.
Imaging tests use x-rays, magnetic fields, sound waves, or radioactive substances to create pictures of the inside of your body. Imaging tests can be done for a number of reasons:
- To help find out whether a suspicious area might be cancer
- To learn how far cancer has spread
- To help determine if treatment has been effective
- To look for signs of the cancer coming back
Unlike most other cancers, doctors can often diagnose kidney cancer fairly certainly based on imaging tests without doing a biopsy (removing a sample of the tumor to be looked at under a microscope). In some patients, however, a biopsy may be needed to be sure.
Computed tomography (CT) scans, magnetic resonance imaging (MRI) scans, and ultrasound can be very helpful in diagnosing most kinds of kidney tumors, although patients rarely need all of these tests. Other tests described here, such as chest x-rays and bone scans, are more often used to help determine if the cancer has spread (metastasized) to other parts of the body.
Computed tomography (CT) scan
The CT scan uses x-rays to produce detailed cross-sectional images of your body. It is one of the most useful tests for finding and looking at a tumor in your kidney. It can provide precise information about the size, shape, and position of a tumor. It is also useful in checking to see if a cancer has spread to nearby lymph nodes or to organs and tissues outside the kidney. If a kidney biopsy is needed, this test can also be used to guide a biopsy needle into the mass to obtain a sample.
Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around you. A computer then combines these pictures into images of slices of the part of your body being studied.
A CT scanner has been described as a large donut, with a narrow table that slides in and out of the middle opening. You will need to lie still on the table while the scan is being done. CT scans take longer than regular x-rays, and you might feel a bit confined by the ring while the pictures are being taken.
Before the test, you might be asked to drink 1 to 2 pints of a liquid called oral contrast. This helps outline the intestine so that certain areas are not mistaken for tumors. You might also receive an IV (intravenous) line through which a different kind of contrast dye (IV contrast) is injected. This helps better outline structures in your body. The injection may cause some flushing (a feeling of warmth, especially in the face). Some people are allergic and get hives. Rarely, more serious reactions like trouble breathing or low blood pressure can occur. Be sure to tell the doctor if you have any allergies or if you have ever had a reaction to any contrast material used for x-rays.
CT contrast can damage the kidneys. This happens more often in patients whose kidneys are not working well in the first place. Because of this, your kidney function will be checked with a blood test before you get IV contrast.
Magnetic resonance imaging (MRI) scan
Like CT scans, MRI scans provide detailed images of soft tissues in the body. But MRI scans use radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed and then released in a pattern formed by the type of body tissue and by certain diseases. A computer translates the pattern into a very detailed image of parts of the body.
A contrast material called gadolinium is often injected into a vein before the scan to better see details. This contrast material isn’t used in people on dialysis, because in those people it can rarely cause a severe side effect called nephrogenic systemic fibrosis.
MRI scans take longer than CT scans − often up to an hour – and are a little more uncomfortable. You have to lie inside a narrow tube, which is confining and can upset people with claustrophobia (a fear of enclosed spaces). Special, open MRI machines can sometimes help with this if needed, but the drawback is that the pictures may not be as clear. MRI machines also make buzzing and clicking noises that many people find disturbing. Some centers provide headphones with music to block this noise out.
MRI scans are used less often than CT scans in people with kidney cancer. They may be done in cases where CT scans aren’t practical, such as if a person can’t have the CT contrast dye because they have an allergy to it or they don’t have good kidney function. MRI scans may also be done if there’s a chance that the cancer has grown into major blood vessels in the abdomen (like the inferior vena cava), because they provide a better picture of blood vessels than CT scans. Finally, they may be used to look for possible spread of cancer to the brain or spinal cord if a person has symptoms that suggest this might be the case.
Ultrasound uses sound waves to create images of internal organs. For this test, a small, microphone-like instrument called a transducer is placed on the skin near the kidney after a gel is applied. The transducer gives off sound waves and picks up the echoes as they bounce off the tissues in the kidney. The echoes are converted by a computer into a black and white image that is displayed on a computer screen. This test is painless and does not expose you to radiation.
Ultrasound can help find a kidney mass and show if it is solid or filled with fluid (kidney tumors are more likely to be solid). Different echo patterns also can help doctors tell some types of benign and malignant kidney tumors from one another.
If a kidney biopsy is needed, this test can also be used to guide a biopsy needle into the mass to obtain a sample.
Positron emission tomography (PET) scan
In a PET scan, a form of radioactive sugar (known as fluorodeoxyglucose or FDG) is injected into the blood. The amount of radioactivity used is very low and will pass out of the body over the next day or so. Because cancer cells in the body are growing quickly, they absorb more of the radioactive sugar. After about an hour, you will be moved onto a table in the PET scanner. You lie on the table for about 30 minutes while a special camera creates a picture of areas of radioactivity in the body. The picture is not finely detailed like a CT or MRI scan, but it provides helpful information about your body.
This test can help spot small collections of cancer cells and can be useful in seeing if the cancer has spread to lymph nodes near the kidney. PET scans can also be useful if your doctor thinks the cancer may have spread but doesn’t know where. PET scans can be used instead of doing multiple x-rays because they scan your whole body.
Special machines can perform both a PET and CT scan at the same time (PET/CT scan). This lets the doctor compare areas of higher radioactivity (suggesting an area of cancer) on the PET with the more detailed image from the CT. Still, PET and PET/CT scans are not a standard part of the work-up for kidney cancers.
An intravenous pyelogram (IVP) is an x-ray of the urinary system taken after a special dye is injected into a vein. The kidneys remove the dye from the bloodstream and it then concentrates in the ureters and bladder. An IVP can help find abnormalities of the renal pelvis and ureter, such as cancer, but this test is not often used when kidney cancer is suspected.
This type of x-ray also uses a contrast dye, although not the same as the one used for an IVP. A catheter is usually threaded up a large artery in your leg into the artery leading to your kidney (renal artery). The dye is then injected into the artery, and x-rays are taken to identify and map the blood vessels that supply a kidney tumor.
This test can help in planning surgery for some patients. Angiography can also help diagnose renal cancers since the blood vessels usually have a special appearance with this test.
Angiography can often be done as a part of a CT or MRI scan, instead of as a separate x-ray test. This means less contrast dye is used, which is helpful since the dye can damage kidney function further if it is given to people whose kidneys aren’t working well.
If kidney cancer has been diagnosed (or is suspected), your chest may be x-rayed to see if cancer has metastasized (spread) to your lungs. The lungs are a common site of kidney cancer metastasis, but this is not very likely unless the cancer is far advanced.
This x-ray can be done in any outpatient setting. If the results are normal, you probably don’t have cancer in your lungs. Still, if your doctor has reason to suspect lung metastasis (based on symptoms like shortness of breath or a cough), you may have a chest CT scan instead of a regular chest x-ray, because it can show more detail.
A bone scan can help show if a cancer has spread to your bones. It might be done if there is reason to think the cancer might have spread to the bones (because of symptoms such as bone pain or blood test results showing an increased calcium level). PET scans can usually show the spread of cancer to bones as well, so if you’ve had a PET scan you might not need a bone scan.
For this test, a small amount of low-level radioactive material is injected into a vein (intravenously, or IV). The substance settles in areas of damaged bone throughout the entire skeleton in a couple of hours. You then lie on a table for about 30 minutes while a special camera detects the radioactivity and creates a picture of your skeleton.
Areas of active bone changes attract the radioactivity and show up as “hot spots” on your skeleton. These areas might suggest cancer spread, but arthritis or other bone diseases can also cause the same pattern. To distinguish between these conditions, your cancer care team may use other imaging tests such as simple x-rays or MRI scans to get a better look at the areas that light up, or they may even take biopsy samples of the bone.
Fine needle aspiration and needle core biopsy
Unlike with most other types of cancer, biopsies are not often used to diagnose kidney tumors. Imaging tests usually provide enough information for a surgeon to decide if an operation is needed. The diagnosis is then confirmed when part of the kidney that was removed is looked at under a microscope.
However, a biopsy is sometimes used to get a small sample of cells from an area that may be cancer when the results of imaging tests are not clear enough to warrant surgery. Biopsy may also be done to confirm a cancer diagnosis if a person might not be treated with surgery, such as with small tumors that will be watched and not treated, or when other treatments are being considered.
Fine needle aspiration (FNA) and needle core biopsy are 2 types of kidney biopsies that may be done. For these types of biopsies a needle is put through the skin to take a sample of cells (called a percutaneous biopsy).
For either type of biopsy, the skin where the needle is to be inserted is first numbed with local anesthesia. The doctor directs the biopsy needle into the area while looking at your kidney with either ultrasound or CT scans. Unlike ultrasound, CT doesn’t provide a continuous picture, so the needle is inserted in the direction of the mass, a CT image is taken, and the direction of the needle is guided based on the image. This is repeated a few times until the needle is within the mass.
For FNA, a small sample of the target area is sucked (aspirated) through the needle into a syringe. The needle used for FNA biopsy is thinner than the ones used for routine blood tests. The needle used in core biopsies is larger than that used in FNA biopsy. It removes a small cylinder of tissue. Either type of sample is checked under the microscope to see if cancer cells are present.
In cases where the doctors think kidney cancer might have spread to other sites, they may take a sample of the metastatic site instead of the kidney.
The Fuhrman grade is found by looking at kidney cancer cells (taken during a biopsy or during surgery) under a microscope. Many doctors use it to describe how quickly the cancer is likely to grow and spread. The grade is based on how closely the cancer cells’ nuclei (the part of the cell in which DNA is stored) look like those of normal kidney cells.
Renal cell cancers are usually graded on a scale of 1 through 4. Grade 1 renal cell cancers have cell nuclei that look a lot like normal kidney cell nuclei. These cancers usually grow and spread slowly and tend to have a good prognosis (outcome). At the other extreme, grade 4 renal cell cancer nuclei look quite different from normal kidney cell nuclei. These cancers have a worse prognosis.
Although the cell type and grade can sometimes help predict prognosis (outlook), the cancer’s stage is by far the best predictor of survival. The stage describes the cancer’s size and how far it has spread beyond the kidney. Staging is explained in “ How is kidney cancer staged?”
Last Medical Review: February 24, 2014 Last Revised: May 16, 2016