Kidney Cancer DIAGNOSE - CT vs MRI

How is kidney cancer diagnosed?

Signs and symptoms of kidney cancer

Unfortunately, early kidney cancers do not usually cause any signs or symptoms, but larger ones may. Some possible signs and symptoms of kidney cancer include:

• Blood in the urine (hematuria)
• Low back pain on one side (not caused by injury)
• A mass (lump) on the side or lower back
• Fatigue
• Unexplained weight loss
• Fever that is not caused by an infection and that doesn't go away after a few weeks
• Swelling of ankles and legs (edema)

These symptoms may be caused by cancer, but more often they are caused by non-cancerous diseases. For example, blood in the urine may be a sign of kidney, bladder, or prostate cancer, but most often it is caused by a bladder infection or a kidney stone. Still, if you have any of these symptoms, consult a doctor so that the cause can be evaluated and treated, if needed.

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 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 and/or the results of the physical exam suggest kidney cancer might be present, more involved tests will likely be done. These might include imaging tests and/or lab tests.

Imaging tests

Imaging tests use x-rays, magnetic fields, or radioactive substances to create pictures of the inside of your body. Imaging tests may be done for a number of reasons, including to help find out whether a suspicious area might be cancerous, to learn how far cancer may have spread, and to help determine if treatment has been effective.

Unlike most other cancers, doctors can often diagnose a kidney cancer fairly certainly without the need for a biopsy (removal of a sample of the tumor to be looked at under a microscope). Often, imaging tests can give doctors a reasonable amount of certainty that a kidney mass is (or is not) cancerous. In some patients, however, a biopsy may be needed to be sure.

Computed tomography (CT) scans, magnetic resonance imaging (MRI) scans, intravenous pyelograms, 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 computed tomography (CT or CAT) scan is an x-ray that produces detailed cross-sectional images of your body. Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around you while you lie on a table. A computer then combines these pictures into images of slices of the part of your body being studied.

Before any pictures are taken, you may 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 may 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 ever had a reaction to any contrast material used for x-rays.

CT scans take longer than regular x-rays. You need to lie still on a table while they are being done. During the test, the table moves in and out of the scanner, a ring-shaped machine that completely surrounds the table. You might feel a bit confined by the ring you have to lie in while the pictures are being taken.

CT scanning is one of the most useful tests for finding and looking at a tumor inside your kidney. It is also useful in checking whether or not a cancer has spread to organs and tissues beyond the kidney. The CT scan will provide precise information about the size, shape, and position of a tumor, and can help find enlarged lymph nodes that might contain cancer.

Magnetic resonance imaging (MRI)

Like CT scans, magnetic resonance imaging (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.

MRI scans are a little more uncomfortable than CT scans. First, they take longer -- often up to an hour. Second, 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. 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 is allergic to the CT contrast dye. 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 or ultrasonography

Ultrasound (US) 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. It 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 be helpful in determining if a kidney mass is solid or filled with fluid. The echo patterns produced by most kidney tumors look different from those of normal kidney tissue. Different echo patterns also can distinguish some types of benign and malignant kidney tumors from one another. If a kidney biopsy is needed, this test can be used to guide a biopsy needle into the mass to obtain a sample.

Positron emission tomography (PET) scan

Positron emission tomography (PET) scans involve injecting a form of radioactive sugar (known as fluorodeoxyglucose or FDG) into the blood. The amount of radioactivity used is very low. Because cancers use glucose (sugar) at a higher rate than normal tissues, the radioactivity will tend to concentrate in the cancer. A scanner can spot the radioactive deposits and can create 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 be helpful for spotting small collections of cancer cells and can be useful to see whether the cancer may have 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 several different x-rays because they scan your whole body.

Some newer machines are able to perform both a PET and CT scan at the same time (PET/CT scan). This allows the radiologist to compare areas of higher radioactivity (suggesting an area of cancer) on the PET with the appearance of that area on the CT. PET and PET/CT scans are not a standard part of the work-up for kidney cancers.

Intravenous pyelogram

An intravenous pyelogram (IVP) is an x-ray of the urinary system taken after a special dye is injected into a vein. This dye is removed from the bloodstream by the kidneys and then concentrates in the ureters and bladder. An IVP can be useful in finding abnormalities of the urinary tract, such as cancer, but you might not need an IVP if you have already had a CT or MRI.

Angiography

Like the IVP, this type of x-ray also uses a contrast dye. 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 to outline blood vessels. This can allow the blood vessels that supply a kidney tumor to be identified and mapped, which can help in planning surgery in some patients. Angiography can also help diagnose renal cancers since the blood vessels usually have a special appearance with this test.

Chest x-ray

If kidney cancer has been diagnosed (or is suspected), a plain x-ray of your chest may be done to look for cancer spread to your lungs. Spread to the lungs 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. The lungs are a common site of kidney cancer metastasis. If your doctor thinks there is a chance the kidney cancer has metastasized to your lungs, you may have a chest CT scan instead of a regular chest x-ray.

Bone scan

A bone scan can help show whether a cancer has metastasized (spread) to your bones. 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 appear as "hot spots" on your skeleton -- that is, they attract the radioactivity. These areas may suggest the presence of 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.

Bone scans are done mainly when there is reason to think the cancer may have spread to the bones (like when the patient is having bone pain or blood test results show 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.

Lab tests

Lab tests are not usually used to diagnose kidney cancer, but they can sometimes give the first hint that there may be a kidney problem. They are also done to get a sense of a person's overall health and to help tell if cancer may have spread to other areas. They can help tell if a person is healthy enough to have an operation.

Urinalysis

Urinalysis (urine testing) is sometimes part of a complete physical exam, but it may not be done as a part of more routine physicals. It is likely to be one of the first tests done if kidney cancer is a possibility.

Microscopic and chemical tests are done on the urine 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. Sometimes special microscopic examination of urine samples (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 different cells in the blood, such as the red blood cells, the white blood cells, and the platelets. This test 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 makes 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 may have kidney cancer, as it can affect the levels of certain chemicals in the blood. For example, high levels of liver enzymes are sometimes found, although the reasons for this are not known. High blood calcium levels may indicate that cancer is spread to the bones, and may therefore prompt a doctor to order a bone scan.

Fine needle aspiration and needle core biopsy

Biopsies are not often used to diagnose kidney tumors. Imaging studies usually provide enough information for a surgeon to decide if an operation is needed. However, fine needle aspiration (FNA) biopsy or needle core biopsy is sometimes used to get a small sample of cells from a suspicious area if imaging test results are not conclusive enough to warrant removing a kidney. Biopsy may also be done to confirm the diagnosis of cancer if a person's health is too poor for surgery and other local treatments (such as radiofrequency ablation, arterial embolization or cryotherapy) are being considered.

Fine needle aspiration and needle core biopsy are 2 types of percutaneous kidney biopsies (percutaneous means that a needle is placed through the skin to take a sample of some internal organ or tissue).

For either type of percutaneous biopsy, the skin where the needle is to be inserted is first numbed with local anesthesia. The doctor directs a hollow 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) 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 (about 1/16- to 1/8-inch in diameter and ½-inch long). Either type of sample is checked under the microscope to see if cancer cells are present.

In cases where the doctors think kidney cancer may have spread to other sites, they may take a sample of the metastatic site instead of the kidney.

Fuhrman grade

The Fuhrman grade is found by looking at kidney cancer cells (taken during a biopsy or during surgery) under a microscope. It is used by many doctors as a way to describe how aggressive the cancer is likely to be. The grade is based on how closely the cancer cells' nuclei (part of a 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 differ very little from normal kidney cell nuclei. These cancers usually grow and spread slowly and tend to have a good outlook (prognosis). At the other extreme, grade 4 renal cell cancer nuclei look quite different from normal kidney cell nuclei and have a worse prognosis.

Although the cell type and grade are sometimes helpful in predicting a prognosis, 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 the section, "How is kidney cancer staged?"

Last Medical Review: 02/18/2010
Last Revised: 07/20/2010