How Kidney Cancer Is Diagnosed and Staged

Kidney cancer (renal cell carcinoma) is usually diagnosed using a combination of ultrasound, CT, and MRI scans, along with a careful history, physical exam, blood tests, and urine tests. Once a cancer is diagnosed, the tumor needs to be carefully staged in order to determine the most appropriate treatments.

Going through the diagnostic process can be stressful—you may feel fear and anxiety. Knowing what to expect and how to cope with the wait time and results may help ease some of the emotions.

kidney cancer diagnosis
Illustration by Verywell

Self Checks/At-Home Testing

Kidney cancer can't be diagnosed at home, but since there is not currently a screening test, having an awareness of the possible signs and symptoms of the disease is something everyone can do.

In particular, if you note that you have blood in your urine (any amount), flank pain, a flank mass, feel tired or have lost your appetite, or lose weight without trying, make sure to see your healthcare provider.

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Labs and Tests

An evaluation for kidney cancer often begins with a careful history, looking for risk factors for the disease, a physical exam, and laboratory tests.

Physical Exam

A physical exam is done with special attention given to checking for a mass in the abdomen, flank, or back, as well as checking blood pressure. The kidneys play an important role in regulating blood pressure, and tumors may result in persistent high blood pressure that is sometimes dangerously high (malignant hypertension).

An exam also includes an evaluation of the genitalia in males. Kidney cancer is unique in that it may cause a varicocele, an enlarged vein (varicose vein) in the scrotum or testicle. Unlike many causes of a varicocele, those due to kidney cancer do not go away when a man lies down.

Lab Tests

The diagnostic work-up of a possible kidney cancer often begins with a urinalysis, a test done not to only to look for blood in your urine, but signs of infection, protein, and more. Roughly half of people with kidney cancer will have some amount of blood in their urine.

complete blood count (CBC) is an important test, as anemia (a low red blood cell count) is the most common initial sign of the disease. Kidney function tests are also important, although these may be normal.

Kidney cancer is also unique in that it can cause elevations in liver function tests, even without the cancer spreading to the liver. This sign is one of the paraneoplastic syndromes that can occur when these tumor cells secrete substances or hormones. Paraneoplastic signs may also include an elevated calcium level in the blood (hypercalcemia), though this may also occur when the cancer spreads to bones.


A number of different imaging modalities may be used for both the diagnosis and staging of kidney cancer.


Ultrasound uses sound waves to provide a picture of structures in the abdomen. It is often the first test done and is particularly helpful in differentiating simple cysts (which are almost always benign), from solid tumors or solid tumors with cystic parts.

CT Scan

CT scans use a series of X-rays to give a cross-sectional picture of a region of the body such as the kidney. In addition to defining a kidney cancer, a CT scan can give important information for staging by evaluating whether it appears that the cancer has spread outside of the kidney or to lymph nodes.

A CT scan is usually done first without contrast, and then with a radiocontrast dye. The dye can sometimes pose concern for people who have kidney dysfunction, in which case a different imaging test may be used.

CT's are an excellent test for characterizing kidney cancers but are frequently unable to determine if the cancer has spread into the renal vein, the large vein exiting the kidney that joins with the inferior vena cava (the large vein that brings blood from the lower body back to the heart).

MRI Scan

An MRI scan uses magnetic imaging instead of X-ray technology to create a picture of structures in the abdomen. In it particularly helpful for defining "soft tissue" abnormalities. In general, a CT scan is a better test for evaluating kidney cancer, but an MRI may be needed for those who have abnormal kidney function tests or who have an allergy to contrast dye.

An MRI may also be considered if a kidney cancer is thought to have spread into the renal vein and inferior vena cava, as special procedures may then be required during surgery. MRI cannot be used by people who have metal in their body, such as a pacemaker, shrapnel, or bullet fragments, as the strong magnets could lead to movement of these objects.

An MRI of the brain may be done to look for evidence of metastases (spread) of the cancer to the brain, the third most common location to which kidney cancer spreads.

PET Scan

PET scans are used frequently in cancer diagnosis, but much less so in the diagnosis of kidney cancer. During a PET scan, a small amount of radioactive sugar is injected into the body and images (usually combined with CT) are taken after the sugar has had time to be absorbed.

Unlike CT and MRI, it is considered a functional test rather than a structural test and may be useful in distinguishing areas of active tumor growth from areas such as scar tissue.

Intravenous Pyelogram (IVP)

An IVP is a test in which dye is injected into a vein. The kidneys then take up this dye, allowing radiologists to view the kidneys, especially the renal pelvis.

IVPs are done infrequently in the diagnosis of kidney cancer but may be used for urothelial cell cancers (transitional cell cancers such as cancers of the bladder and ureter than can sometimes include the central portion of the kidneys, the renal pelvis).

Renal Angiography

Angiography is often done in combination with a CT scan and involves injecting a dye into the renal artery to define the blood vessels of the kidney. This test is sometimes used to help plan for surgery for a tumor.

Cystoscopy and Nephro-Ureteroscopy

These tests involved inserting a lighted catheter into the bladder, through the ureter, and up to the renal pelvis (the "center" of the kidney). It is used primarily if there is also a mass in the bladder or ureter, such as transitional cell carcinoma.


While a biopsy is essential in diagnosing many cancers, it is not often necessary for diagnosing kidney cancer. In addition, there is a risk with fine needle biopsies (biopsies done with a thin needle inserted through the skin and into the kidney) that the procedure could "seed" the tumor (spread the tumor alone the pathway of the needle).

Samples of a tumor are important for planning treatment, such as with targeted therapies, but are most often obtained during surgery instead of a biopsy.

Tests for Metastases

Kidney cancer can spread either through the bloodstream or through the lymphatic vessels, and the most common sites of metastases are the lungs, bones, and brain, in that order. A chest X-ray (or chest CT) may be done to look for lung metastases.

Either a bone scan or PET scan can determine if bone metastases are present. An MRI of the brain is the best test to look for brain metastases.

Differential Diagnosis

Unlike many cancers, there are relatively few causes of a mass in the kidney. The differential diagnosis, however, can be more difficult when a small mass is found in the kidney, usually incidentally when a test is done for another reason.

Other possible causes of a renal mass include:

  • Renal (kidney) cysts: Cysts can often be differentiated with an ultrasound and are often found with polycystic kidney disease.
  • Angiomyolipomas: An angiomyolipoma can be differentiated from kidney cancer during a CT scan (due to the presence of fat). These are benign tumors.
  • Oncocytomas: Oncocytomas are also usually differentiated based on CT findings. These benign tumors can sometimes closely mimic kidney cancer on imaging studies.
  • Renal adenomas: These are benign tumors that are frequently an incidental finding on imaging tests.
  • Urothelial cancers (transitional cell cancers of the bladder, ureters, and sometimes renal pelvis): These cancers make up roughly 15% of kidney cancers and are usually located centrally in the kidney and involve the collecting system. Cancers cells may be present on a urinalysis.
  • Adrenal tumors: The adrenal glands sit on top of the kidneys and can usually be differentiated on imaging. The most common adrenal tumors are adrenal metastases from cancers such as lung cancer.
  • Renal abscess: An abscess is a walled off infection.
  • Kidney metastases: Several types of cancer may spread to the kidneys. This frequently causes a few small spots rather than a larger tumor. Cancers that may spread to the kidneys include lung cancer, breast cancer, stomach cancer, melanoma, and cancers of the other kidney.
  • Hodgkin's lymphoma and non-Hodgkin's lymphoma: Both of these blood-related may also involve the kidneys, but are often associated with tumors (and enlarged lymph nodes) in other parts of the body as well.
  • Renal infarct: An infarct refers to a lack of blood supply. This is like a "heart attack" of the kidney, and the dead tissue (necrotic tissue) can sometimes appear as a mass on imaging.
  • Sarcomas: These are rare cancers that begin in the soft tissue that surrounds the kidney.

Staging Kidney Cancer

Staging a kidney cancer is usually done after surgery and combines the results of imaging tests along with characteristics of tumor which is sent to pathology after surgery, as well as findings during surgery.

Tumor Grade

Kidney cancers are given a grade of 1 to 4, called the Fuhrman grade, that is a measure of the aggressiveness of a tumor.

A grade of 1 is used to describe tumors that are the least aggressive and have cells that are very differentiated (look the most like normal kidney cells). In contrast, a grade of 4 is given to describe the most aggressive appearing tumors, those that are very undifferentiated and look very different from normal kidney cells.

renal cell carcinoma: stage at diagnosis
Illustration by Verywell

TNM Staging

Kidney tumors are also evaluated using something called the TNM system. This can be confusing at first but is much easier to understand if we define these letters and what the numbers mean.

  • T stands for tumor. The numbers following the T indicate the size of the tumor. T1 tumors are less than 7 cm in diameter. T2 tumors are 7 to 10 cm in diameter. T3 tumors have grown beyond the kidney or into a vein, but not into the adrenal glands or beyond Gerota's fascia (the layer of tissue that surrounds the kidney). T4 tumors have grown beyond Gerota's fascia or into the adrenal gland.
  • N stands for nodes. A description of N0 would mean that the cancer has not spread to any lymph nodes. N1 would mean that the cancer has spread to lymph nodes nearby.
  • M stands for metastases and is either 0 or 1 depending on whether metastases are present (whether the cancer has spread to the lungs, bones, brain, or other regions). M0 means no metastases are present. M1 means metastases are present.

Tx (or Nx or Mx) means that the tumor (or nodes or metastases) cannot be assessed. T0 means there is no evidence of a primary tumor and is used if kidney metastases are found, but the primary tumor cannot be located.


Using the letters above, kidney cancers are then divided into 4 stages:

  • Stage 1: Stage 1 kidney cancers (T1, N0, M0) are less than 7 cm in diameter and are located in the kidney (they haven't spread to lymph nodes or any other areas of the body).
  • Stage 2: In this stage (defined as T2, N0, M0) the cancer may be larger than 7 cm in diameter and limited to the kidney. It has not, however, spread to any lymph nodes, the adrenal glands, Gerota's fascia, or distant sites.
  • Stage 3: Stage 3 tumors (that can be T1 or T2, N1, M0, or T3, any N, M0) may be any size but have not spread beyond Gerota's fascia. This category also includes tumors that have not grown beyond the kidney, but have spread to a nearby lymph nodes.
  • Stage 4: Stage 4 is defined in two primary ways. In one setting, the tumor may have spread beyond Gerota's fascia with or without involvement of nearby lymph nodes, but not to other regions of the body. Or it may be of any size, have spread to any nodes, and also have spread to other regions of the body (Any T, Any N, M1).

Recurrent Kidney Cancer

Recurrent kidney cancer refers to any cancer which has come back, whether within the kidney, in surrounding tissues, in lymph nodes, or in distant sites.

All the diagnostic tests performed will help your healthcare provider accurately stage your tumor. Based on the results, he or she will be better able to choose a treatment tailored to your situation.

Frequently Asked Questions

  • Can a blood test tell whether you have kidney cancer?

    No. A blood test can’t be used to diagnose kidney cancer. However, your healthcare provider will run blood tests to check red blood cell levels and measure liver function, since kidney cancer can interfere with these.

  • Should I get a second opinion after a kidney cancer diagnosis?

    If you have time before starting treatment, it may be best to get a second opinion for kidney cancer or any type of cancer. This is recommended especially if:

    • Your healthcare provider is not an expert in kidney cancer
    • You’ve been diagnosed with rare sarcomas
    • Your insurance company requires it
    • There’s uncertainty about the stage of your cancer
  • Is a biopsy necessary to diagnose kidney cancer?

    Not usually. Imaging tests often provide enough information to determine the stage and best way to treat kidney cancer. Taking a sample may be necessary in some instances, or a biopsy of metastatic sites may be needed.

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Additional Reading

By Lynne Eldridge, MD
 Lynne Eldrige, MD, is a lung cancer physician, patient advocate, and award-winning author of "Avoiding Cancer One Day at a Time."