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Diagnosing Kidney Disease

At NYU Langone, specialists called nephrologists diagnose and manage kidney disease. In this chronic condition, the kidneys slowly lose their ability to filter waste from the blood. If this condition isn’t managed, it can lead to kidney failure, in which one or both kidneys no longer function. Some people may experience acute kidney failure, in which the organs fail in less than two days.

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The kidneys are small, bean-shaped organs, each about the size of a fist, located under the rib cage in the back. They have several important functions, including removing digested food, chemicals, medication, and other waste products from the blood. These are then excreted in urine.

The kidneys also balance the body’s levels of fluids and electrolytes, such as phosphorus, potassium, and sodium. These are essential for the proper functioning of the heart, muscles, and other structures. The kidneys also make hormones that help regulate blood pressure, stimulate the production of red blood cells, and strengthen bones.

When the kidneys are not able to function properly, the body retains toxins and excess fluid and can fail to make enough red blood cells, which carry oxygen to organs and tissue.

Some people with chronic kidney disease experience no symptoms. They may receive a diagnosis only after having blood or urine testing for another condition.

Symptoms of kidney disease may include shortness of breath, weakness, fatigue, lack of appetite, and swelling in the legs or abdomen as waste products build up in the body. Abnormal heart rhythms caused by excess potassium in the blood can also occur. Scarring and changes in blood flow can cause the kidneys to produce a salt-retaining hormone that can lead to fluid retention.

Risk factors for chronic kidney disease include diabetes, lupus, high blood pressure, and polycystic kidney disease, an inherited condition that causes cysts to develop on the kidneys. African Americans with chronic kidney disease are more likely to experience kidney failure in part because of mutations, or changes, in a gene called APOL1.

You may be at risk for acute kidney failure if you’ve experienced a serious systemic infection, a severe injury, or cardiac arrest, which can affect blood flow to the kidneys.

Causes of kidney failure include inflammation in the kidneys or in the organs’ blood vessels, diabetes, hypertension, lupus, and polycystic kidney disease. Sometimes the kidneys fail suddenly after surgery, a heart attack, or a severe illness. Excessive amounts of some medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs), can also cause the kidneys to fail.

Diagnostic Tests

Your NYU Langone doctor asks about your medical history to determine if you have any conditions that might increase your risk for kidney disease. He or she also performs a physical exam to check your blood pressure and heart rate and look for swelling in your legs and abdomen. Your doctor may then recommend one or more tests.

Blood Testing

Your doctor may order a blood test to check the levels of waste substances, including creatinine and urea. A blood creatinine test helps the doctor determine the kidneys’ level of function by providing information about the glomerular filtration rate, a measurement of how well the kidneys are filtering blood.

A blood urea nitrogen test measures levels of a waste product called urea nitrogen in the blood. Urea nitrogen is made in the liver and passes through the kidneys for filtering before being excreted in urine. High levels can indicate that the kidneys are not working properly.

Blood tests can also determine if you have anemia, in which the body doesn’t make enough red blood cells, which carry oxygen to tissue and organs in the body. Healthy kidneys produce a hormone called erythropoietin, which triggers the bone marrow to produce red blood cells.

Urine Testing

A urine sample may be tested to determine if blood and certain proteins, such as albumin, are present. These substances can leak into urine when the kidneys aren’t functioning properly. Levels of protein and white and red blood cells in the urine can help the doctor pinpoint the abnormality in the kidneys.


An ultrasound uses sound waves to produce images of the kidneys and other parts of the urinary system. Your doctor may perform an ultrasound to determine the size of the kidneys. Smaller kidneys suggest that kidney disease is chronic.

The doctor also looks for any obstructions that may be hindering the kidneys’ ability to filter waste products. In addition, he or she assesses blood flow to the kidneys and checks for scarring, which can indicate the length of time kidney function has been impaired.

During the test, a small handheld device called a transducer is placed on the abdomen. The images are then displayed on a computer screen.

Our Research and Education in Kidney Disease

Learn more about our research and professional education opportunities.