Can a CT Scan Accurately Diagnose Kidney Cancer?

Your kidneys play a vital role in filtering waste from your blood and getting rid of this waste through urine. Additionally, your kidneys help control your blood pressure and also help stimulate bone marrow to produce red blood cells. When kidney cancer develops, it can affect these critical functions.

In many cases, kidney cancer has no symptoms. If symptoms or signs of kidney cancer were to develop, the most common would include:

• blood in your urine
• persistent pain in your lower back
• a mass or lump in your abdominal area
• anemia
• recurring fever
• constant fatigue
• swelling (edema) in your legs, ankles, or feet
• reduced appetite
• unintentional weight loss

If you experience any of these symptoms, it’s important to see a doctor right away for an accurate diagnosis. They may order a combination of tests to help identify the underlying issue, such as:

• imaging tests to get a clear look at the kidneys, particularly a CT scan
• a urine test (urinalysis)
• blood testing
• examination for cancerous cells in your urine (urine cytology)
• biopsy, if an unusual mass is found and the other tests aren’t conclusive

A CT scan is an advanced type of X-ray procedure that uses narrow beams of electromagnetic radiation to create two-dimensional (2D) cross-sectional images of the inside of your body. These images are then sent to a computer for detailed analysis. Occasionally, the 2D images are reconstructed to create a three-dimensional (3D) picture.

According to the American Cancer Society, a CT scan is a valuable diagnostic tool for kidney cancer because it not only shows the exact location of a suspected tumor but can also provide details regarding the tumor shape and size.

Furthermore, a CT scan can show whether cancer has spread beyond the kidneys to nearby lymph nodes or other areas of the body.

It’s also possible for a CT scan to find kidney cancer even if the CT scan was originally ordered for a different purpose. This is known as an incidental finding.

A CT scan is done inside a donut-shaped machine called a gantry, where you lie on a rigid board. As you lie still on the board, the surrounding tube circles around your body, emitting X-rays that are then transmitted to a computer in the form of images.

CT scans have the ability to take images of organs, bones, and the presence of excess fluid. However, soft tissues such as muscles and organs are sometimes hard to identify in these imaging tests.

To get better visual definition, sometimes intravenous (IV) contrast agents (dyes) can be helpful. The dye will be injected via an IV line while you’re lying on the board inside the CT scanner.

CT scans with contrast dyes have an overall high accuracy rate for detecting small renal masses. One diagnostic accuracy study even estimated the accuracy rate of detecting kidney tumors to be higher than 99 percent.

Compared with other types of cancer, kidney cancers can be solely diagnosed by using a CT scan. This can save time spent waiting on other diagnostic tests, allowing you to get started with a treatment plan as soon as possible.

Occasionally, a biopsy may still be warranted. This involves taking a small sample of the tumor or mass and sending it to a lab for further analysis to determine if it’s cancer.

Also, once you’ve started treatment for kidney cancer, CT scans can help determine how well these treatments are working. These tests can help determine whether the tumor has gotten smaller or been eliminated.

Other possible imaging tests a doctor may consider in diagnosing kidney cancer include:

• an ultrasound to help look for kidney tumors or to help guide a fine-needle biopsy procedure
• an angiogram to help map any blood vessels that could be feeding a kidney tumor
• a magnetic resonance imaging (MRI) scan if contrast dyes aren’t safe for you, or if additional soft tissue detail is required. This is also useful in planning surgical strategies, if needed.
• chest X-rays to see if the cancer has spread to your lungs
• a bone scan to see if the cancer has spread to the bones

While contrast dyes are a necessary component of a CT scan for kidney cancer, these dyes may pose certain risks to the kidneys. For example, the dyes can cause temporary kidney failure or reduce kidney function.

For this reason, a doctor will do a blood test to determine your overall kidney function before you undergo a CT scan with IV contrast dyes. If there are issues with your kidney function, a doctor may decide to use other diagnostic tools instead.

Although it’s rare, contrast dyes can cause allergic reactions in some people.

While a CT scan uses a small amount of radiation, the risk of developing cancer from these diagnostic imaging tests is considered small.

A CT scan offers a quick and accurate way to detect kidney cancer and to get started with the right treatment.

While diagnosing kidney cancer with a CT scan isn’t completely risk-free, it’s considered a reliable tool overall. If you’re allergic to contrast dye, or if you have issues with your kidney function, a doctor may opt to use a different diagnostic test.

If you’re concerned that you may have symptoms of kidney cancer, talk with a doctor about the methods and tests that are available for kidney cancer detection and about which one is safest and best suited to you.