Understanding Kidney Cancer

How Is Kidney Cancer Diagnosed?

Last updated and reviewed on June 13, 2026.

Getting the right diagnosis is one of the most important steps on your kidney cancer journey. The process usually begins either when a patient notices a symptom (like blood in the urine or back pain) and sees a doctor, or when a kidney mass is found unexpectedly during an imaging test done for another reason. From there, doctors use a combination of imaging tests, lab work, and sometimes a biopsy to confirm the diagnosis, determine the type of cancer, and figure out how far it has spread. The more complete and accurate the diagnosis, the better your care team can plan the best treatment.

What Tests Are Used to Diagnose Kidney Cancer?

Medical History and Physical Exam. Your doctor will start by asking about your symptoms, how long you have had them, whether they are getting worse, and whether you have any known risk factors for kidney cancer (like a family history, smoking history, or high blood pressure). A physical exam will check for any lumps or tenderness in the abdomen or flank. While a physical exam alone cannot diagnose kidney cancer, it gives important clues that guide the next steps.

Urine Tests (Urinalysis). A urine test (urinalysis) checks for blood in the urine (hematuria), which can be a warning sign for kidney cancer or another urinary condition. Even microscopic amounts of blood that cannot be seen with the naked eye can show up on a urinalysis. Other urine tests look for abnormal cells (urine cytology), which is especially useful if urothelial carcinoma of the renal pelvis is suspected.

Blood Tests. Blood tests cannot diagnose kidney cancer directly, but they give important information about your overall health and kidney function. Common blood tests include:

• Complete blood count (CBC): Checks for anemia (low red blood cells), which is common in kidney cancer.
• Comprehensive metabolic panel (CMP): Checks kidney function (creatinine, BUN), liver function, calcium levels, and electrolytes.
• Erythrocyte sedimentation rate (ESR): May be elevated with kidney cancer.
• Lactate dehydrogenase (LDH): Sometimes elevated in advanced kidney cancer.

Imaging Tests. Imaging is the backbone of kidney cancer diagnosis. It is used to find the tumor, learn about its size and location, check whether it has grown into nearby structures, and look for signs of spread to other organs.

• Ultrasound: Often the first imaging test used when a kidney mass is suspected. It uses sound waves to create images and can tell the difference between a simple fluid-filled cyst (almost always benign) and a solid mass (which may be cancer). Ultrasound does not use radiation and is widely available.
• CT Scan (Computed Tomography): The most important and commonly used test for kidney cancer diagnosis. A CT scan with intravenous contrast dye creates detailed, cross-sectional images that show the size, location, and blood supply of the tumor. It also shows whether the cancer has grown into the renal vein or vena cava (a major blood vessel), spread to nearby lymph nodes, or traveled to the lungs, liver, or other organs. CT of the chest, abdomen, and pelvis is the standard staging scan for kidney cancer.
• MRI (Magnetic Resonance Imaging): Uses magnetic fields and radio waves to create detailed images without radiation. MRI is particularly useful for evaluating whether a tumor has grown into the renal vein or inferior vena cava, and for patients who cannot receive CT contrast dye (due to kidney problems or allergy). MRI is also preferred in pregnancy.
• PET Scan (Positron Emission Tomography): Occasionally used to check for spread to distant organs, though CT scanning is more commonly used for kidney cancer than PET.
• Bone Scan: Done if there is concern that the cancer may have spread to the bones (for example, if a patient has bone pain or elevated blood calcium levels).
• Chest X-Ray: Can detect large lung metastases. However, CT of the chest is more sensitive and is usually preferred.

Biopsy: A biopsy means removing a small sample of tissue from the tumor to examine under a microscope. For kidney cancer, a biopsy is not always needed before treatment — in many cases, the combination of imaging features and clinical information is enough to plan surgery with confidence.

However, a biopsy is recommended when:

• The imaging results are uncertain, and it is not clear if the mass is cancerous.
• The patient is not a surgical candidate, and the treatment decision (such as whether to use targeted therapy) depends on knowing the exact tumor type.
• A metastatic lesion needs to be confirmed and characterized.
• Active surveillance (watchful waiting) is being considered for a small mass.

Kidney biopsies are most commonly done as percutaneous core needle biopsies a needle is guided through the skin into the tumor using ultrasound or CT imaging. The procedure is generally safe and well-tolerated, with a low risk of serious complications.

Pathology and Molecular Testing Once tissue is obtained, a pathologist examines it under a microscope to determine the cancer type, subtype, and grade. In some cases, molecular tests (genetic testing on the tumor cells) are done to identify specific mutations that can guide targeted treatment choices. For example, testing for VHL gene mutations in clear cell RCC, or for TFE3 gene fusions in translocation RCC, can have implications for both prognosis and treatment.

Sources:

1. American Cancer Society. Tests for Kidney Cancer. https://www.cancer.org/cancer/types/kidney-cancer/detection-diagnosis-staging/how-diagnosed.html
2. National Cancer Institute. Renal Cell Cancer Treatment (PDQ) – Patient Version. https://www.cancer.gov/types/kidney/patient/kidney-treatment-pdq
3. Motzer RJ, et al. NCCN Clinical Practice Guidelines: Kidney Cancer. Journal of the National Comprehensive Cancer Network. 2022.
4. Ljungberg B, et al. EAU Guidelines on Renal Cell Carcinoma. European Urology. 2022.
5. Pierorazio PM, et al. Prognostic and clinical significance of the discovery of small renal masses. Urologic Oncology. 2013.