Diagnosing Chronic Kidney Disease in Children

At Hassenfeld Children’s Hospital at NYU Langone, nephrologists who specialize in treating children with kidney conditions are experienced in diagnosing and managing chronic kidney disease.

The kidneys are a pair of small, bean-shaped organs located in the back, below the rib cage. Their main job is to filter waste and excess fluids from the blood and eliminate them through urine. These organs also maintain the proper balance of fluids and minerals needed for nerve and muscle health.

The kidneys have several other functions. They make erythropoietin, a hormone that helps produce red blood cells, and renin, an enzyme that regulates blood pressure. The kidneys also convert vitamin D into a hormone that the body uses to maintain bone metabolism, a process in which the body removes old bone tissue and replaces it with new bone.

Chronic kidney disease is a progressive, irreversible condition that reduces the kidneys’ ability to perform these functions. There are many possible causes of this condition. Depending on the cause and how it’s managed, chronic kidney disease may progress slowly or quickly.

Congenital kidney problems, in which the kidneys and urinary system don’t develop normally, are the most common cause of chronic kidney disease in children. Often, these problems cause an obstruction in urine flow and repeated urinary tract infections, which can further injure the kidneys.

Conditions such as glomerulonephritis, which damages the filtering structures within the kidneys, and lupus, an autoimmune condition that can cause kidney inflammation, may also lead to chronic kidney disease in children.

Some bacteria, such as E. coli and Streptococcus, produce toxins that can damage blood vessels and filtering structures in the kidneys, temporarily impairing kidney function. Rarely, infections with these organisms cause permanent kidney damage.

Signs and Symptoms

Children with chronic kidney disease are usually very tired and have a poor appetite. These symptoms are the result of anemia—a decreased production of oxygen-rich red blood cells—and a buildup of acid in the blood, called acidosis. Children with chronic kidney disease also may urinate less frequently or have low urine output. They may be smaller than other children their age. This is because the body draws calcium out of bones to neutralize excess acids. Also, the kidneys don’t produce enough vitamin D to fuel bone growth.

Over time, children with poor kidney function may retain sodium, or salt, which can cause hypertension. They may also have higher levels of renin, an enzyme that increases blood pressure.

Chronic kidney disease can also lead to a buildup of certain electrolytes, or minerals, in the blood. Too much potassium can cause heart rhythm disturbances, also known as arrhythmias. Too much phosphorous can signal the bones to stop absorbing calcium, which can weaken bones and interfere with a child’s growth.

Eventually, chronic kidney disease leads to kidney failure, also known as end-stage kidney disease. Managing complications such as acidosis and anemia—and preventing hypertension, which can further injure the kidneys—can help slow the progression of the condition.

To diagnose chronic kidney disease, our doctors perform a physical exam and various tests to assess your child’s kidney function and identify underlying causes of the condition. This information is used to determine the most effective treatment and prevent the condition from progressing rapidly.

Physical Exam

During a physical exam, a nephrologist reviews your child’s medical history for any conditions that may cause kidney disease and how well they’re being managed. The doctor also takes your child’s blood pressure and asks about fatigue or other symptoms, such as swelling in the legs, feet, and ankles.

Laboratory Tests

The doctor may collect blood and urine samples to determine how well your child’s kidneys are working. These samples are sent to a laboratory for analysis.

Blood tests may be used to measure the number of blood cells to determine if your child has anemia. These tests also measure levels of electrolytes and vitamins, including bicarbonate, phosphorous, calcium, and potassium, iron, and vitamin D. Additional tests are performed to evaluate the level of lipids, or fats, in the blood, which may increase in children with chronic kidney disease.

Urine tests may measure protein in your child’s urine. Excess protein in the urine can mean that your child’s kidneys aren’t functioning properly.

Blood and urine tests may also reveal how much creatinine, a waste product that forms as muscle tissue breaks down, is eliminated in the urine versus how much remains in the blood. When the kidneys are not functioning normally, more creatinine is found in the blood than in the urine.

Kidney Biopsy

A kidney biopsy is used to diagnose conditions that can cause kidney damage, such as glomerulonephritis and lupus. This procedure is usually performed in the hospital by an interventional radiologist—a doctor who performs procedures with image guidance—using sedation. The doctor numbs a small area of skin on the child’s back with a local anesthetic, then inserts a thin needle into the kidney to remove a tiny amount of tissue.

The tissue sample is sent to a laboratory, where a pathologist—a doctor who studies diseases under a microscope—looks for signs of inflammation.

Identifying Congenital Kidney Problems

Our kidney specialists may also perform tests to find out whether your child’s kidney disease is caused by a congenital condition affecting the kidney or urinary tract. If these tests show a structural problem, our doctors may recommend surgery or other treatments to correct it.

Kidney Ultrasound

Your child’s doctor may order an ultrasound—which uses sound waves to produce images on a high-definition monitor—to establish whether the kidneys are enlarged. The images may also identify blockages in the tubes leading to and from the organs.

In this test, a doctor or technician places a small device called a transducer on your child’s abdomen. This produces an image of the kidneys and other parts of the urinary system.

Voiding Cystourethrogram

A voiding cystourethrogram is an imaging test used in an infant or young child to look for a structural kidney problem or a blockage in the tubes leading to and from the kidneys.

A radiologist inserts a small, flexible tube called a catheter into the child’s urethra—the tube connected to the bladder that carries urine out of the body—and injects a small amount of a contrast agent into the bladder. The doctor then takes an X-ray, which uses energy beams to form an image of organs and other structures in the body. Another X-ray is taken after your child urinates. The test doesn’t require sedation and is usually completed in a half hour.

Renal Scan

A renal scan is a nuclear imaging test that assesses kidney function. It measures how long it takes urine to flow from the kidneys to the bladder. In this test, a radiologist gives your child an injection containing a dye combined with a substance called a radionuclide tracer. The kidneys absorb the tracer, and a nuclear scanner is used to take pictures of the kidneys as the material travels to the bladder. The test doesn’t require sedation.