Diagnosing Kidney Cancer
NYU Langone specialists use the latest techniques to diagnose kidney cancer. One of the top 10 most common cancers, this condition affects more than 60,000 people a year and is more commonly diagnosed in men than women.
The kidneys are two bean-shaped organs located on each side of the spine, just below the rib cage. Their job is to remove waste and extra water from the blood, creating urine. This fluid flows through tubes called ureters to the bladder. From there, it leaves the body through a thin tube called the urethra.
The kidneys also aid in regulating blood pressure and maintaining a balance of certain minerals—electrolytes such as sodium and potassium—that are essential to many functions in the body.
Each kidney has about a million filters, called nephrons. Some types of kidney tumors involve the nephrons. Other types affect the renal pelvis, the structures that funnel urine from the kidneys to the bladder, and the ureters.
Types of Kidney Cancer
Some kidney masses are benign, or noncancerous, and require no treatment.
Renal cell carcinoma accounts for about 90 percent of all kidney cancers. This form of cancer develops in the cells that line the tubules, which are a part of the nephrons located throughout the kidney. The three major subtypes of renal cell carcinoma are categorized according to what the cells look like under a microscope:
- clear cell renal cell carcinoma, in which the cells appear pale or almost clear
- papillary renal cell carcinoma, in which the cancer cells form small projections that look like fingers
- chromophobe renal cell carcinoma, in which the cancer cells appear large and pale
Another form of kidney cancer, transitional or urothelial cell carcinoma, accounts for about 5 to 10 percent of all kidney cancers. This condition develops in the renal pelvis, where the ureters meet the kidney. This type is referred to as upper urinary tract transitional cell carcinoma, or upper urinary tract cancer. Diagnosis and treatment of upper urinary tract cancer differs somewhat from renal cell carcinoma.
Wilms tumor is another type of kidney cancer, but it is rare and occurs mostly in children.
Risk Factors and Symptoms
Risk factors for all kidney cancers include smoking, being overweight, having high blood pressure, and being exposed to toxic substances, such as asbestos and cadmium. Being on long-term dialysis, a treatment for kidney failure that involves removing harmful substances from the blood, can also raise the risk. A family history of kidney cancer and rare genetic syndromes such as von Hippel–Lindau disease, hereditary papillary renal cell carcinoma, and Birt–Hogg–Dubé syndrome also increase risk.
In the past, kidney cancer was only discovered when people experienced common symptoms such as blood in the urine, a pain or lump in the side or lower back, fatigue, a loss of appetite, and weight loss. In recent years, however, imaging tests conducted for unrelated health conditions detect up to 67 percent of kidney tumors before symptoms start. Earlier detection of kidney tumors increases the likelihood that they can be managed with surgery.
To diagnose the condition, your doctor asks about your medical history and any symptoms you may be experiencing. Then, NYU Langone doctors may perform several different tests.
Urine tests do not diagnose kidney cancer, but a doctor may want to see if there is any blood in the urine, a common sign of advanced kidney cancer. Finding blood doesn’t mean you have cancer; it may also signal other conditions, such as a urinary tract infection or kidney stones. About half of people with kidney cancer do not have blood in their urine.
Blood tests help doctors determine if the kidneys are working properly, but, to date, they can’t be used to diagnose kidney cancer. Doctors may use blood tests to check the level of red blood cells in the body and to measure the function of the liver and bone marrow, the spongy tissue found in the center of bones.
Kidney cancer may cause anemia, in which the body lacks healthy red blood cells, which provide oxygen to tissues. Healthy kidneys make a hormone called erythropoietin, which signals the bone marrow to make red blood cells. Kidney cancer can disrupt this process.
If your doctor suspects you have cancer based on your symptoms and the results of urine and blood tests, he or she may order a CT scan, which uses X-rays and a computer to create three-dimensional, cross-sectional images of the kidney.
Before the scan, doctors may inject a contrast agent into a vein to enhance the images. This contrast agent travels throughout the body, allowing your doctor to see clear images of the kidneys and the size, shape, and location of any suspicious lesions or masses. Doctors avoid using a contrast agent in people who have kidney failure because it can further damage the kidneys.
If one or more tumors are found, your doctor uses the scan to determine whether it is cancerous. Cancerous cells may appear solid and brighter than the surrounding healthy tissue.
A CT scan can also help determine whether cancer has spread to nearby lymph nodes, the small glands throughout the body that trap viruses and bacteria, or to the lungs or bone.
Often, NYU Langone doctors rely on MRI scans to diagnose kidney cancer, especially if a CT scan does not provide enough detail.
An MRI scan uses a magnetic field and radio waves to create computerized, highly detailed, three-dimensional images of the anatomy of the kidneys. An MRI can sometimes enable doctors to tell the difference between a potentially cancerous mass, a benign growth such as a cyst, and a noncancerous fatty tumor called an angiomyolipoma. It may help a doctor determine whether a possible cancer has spread to blood vessels, as well as the surrounding organs or lymph nodes.
Doctors may also use MRI to help determine the subtype of tumors present and to measure kidney function by detecting how much blood is being filtered through each kidney.
Often, a contrast agent is injected into a vein to enhance MRI images. This contrast is safe to use in patients with mild or moderate problems with kidney function but not in people who have kidney failure.
CT and MRI scans are usually the only tests doctors need to diagnose kidney cancer. Sometimes, though, doctors perform what’s known as a percutaneous biopsy if they need more information about a tumor before making a treatment recommendation. During this procedure, a doctor numbs the skin using a local anesthetic. Then he or she uses a small needle to withdraw a portion of tissue.
Doctors may use either CT scans or ultrasound—the use of sound waves to create images on a computer monitor—to locate the tumor and guide the insertion and withdrawal of the needle. A pathologist, a doctor who studies diseases in a laboratory, examines the tissue samples under a microscope for signs of cancer.
NYU Langone doctors are studying advanced imaging techniques to diagnose kidney cancer, which could reduce the need for a percutaneous biopsy. These imaging methods may also help predict kidney function after treatment. Radiologists are using special MRI and CT scanning techniques to distinguish between different types of kidney tumors, a process called a virtual biopsy.
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