Childhood Nephrotic Syndrome
Childhood Nephrotic Syndrome
Childhood nephrotic syndrome can occur at any age but is most common between the ages of 1-1/2 and 8 years. It seems to affect boys more often than girls.
A child with the nephrotic syndrome has these signs: High levels of protein in the urine Low levels of protein in the blood Swelling resulting from buildup of salt and water.
The nephrotic syndrome is not itself a disease. But it can be the first sign of a disease that damages the tiny blood-filtering units (glomeruli) in the kidneys, where urine is made.
The kidneys are two bean-shaped organs found in the lower back. They are about the size of a fist. They clean the blood by filtering out excess water and salt and waste products from food. Healthy kidneys keep protein in the blood, which helps the blood soak up water from tissues. But kidneys with damaged filters may let protein leak into the urine. As a result, not enough protein is left in the blood to soak up the water. The water then moves from the blood into body tissues and causes swelling. You may see swelling around your child’s eyes, belly, and legs. Your child may urinate less often than usual and may gain weight from the excess water.
To diagnose childhood nephrotic syndrome, the doctor may ask for a urine sample to check for protein. The doctor will dip a strip of chemically treated paper into the urine sample. Too much protein in the urine will make the paper change color. Or the doctor may ask for a 24-hour collection of urine for a more precise measurement of the protein and other substances in the urine.
The doctor may take a blood sample to see how well the kidneys are removing wastes. Healthy kidneys remove creatinine and urea nitrogen from the blood. If the blood contains high levels of these waste products, some kidney damage may have already occurred. But most children with the nephrotic syndrome do not have permanent kidney damage.
In some cases, the doctor may want to examine a small piece of the child’s kidney under a microscope to see if substances there are causing the syndrome. The procedure of collecting a small tissue sample from the kidney is called a biopsy, and it is usually performed with a long needle passed through the skin. The child will be awake during the procedure and receive calming drugs and a local painkiller at the site of the needle entry. General anesthesia is used in the very rare cases where open surgery is required. The child will stay overnight in the hospital to rest and allow the health care team to ensure that no problems occur.
Minimal Change Disease
The most common form of the nephrotic syndrome in children is called minimal change disease. Doctors do not know what causes it. The condition is called minimal change disease because children with this form of the nephrotic syndrome have normal or nearly normal biopsies. If your child is diagnosed with minimal change disease, the doctor will probably prescribe prednisone, which belongs to a class of drugs called corticosteroids. Prednisone stops the movement of protein from the blood into the urine, but it does have side effects that the doctor will explain. Following the doctor’s directions exactly is essential to protect your child’s health. The doctor may also prescribe another type of drug called a diuretic, which reduces the swelling by helping the child urinate.
When protein is no longer present in the urine, the doctor will begin to reduce the dosage of prednisone. This process takes several weeks. Some children never get sick again, but most do develop swelling and protein in the urine again, usually following a viral illness. However, as long as the child continues to respond to prednisone and the urine becomes protein free, he or she has an excellent long-term outlook without kidney damage.
Children who relapse frequently, or who seem to be dependent on prednisone or have side effects from it, may be given a second type of drug called a cytotoxic agent. The agents most frequently used are cyclophosphamide, chlorambucil, and cyclosporine. After reducing protein in the urine with prednisone, the doctor may prescribe the cytotoxic agent for a while. Treatment with cyclophosphamide and chlorambucil usually lasts for 8 to 12 weeks, while treatment with cyclosporine frequently takes longer. The good news is that most children "outgrow" this disease by their late teens with no permanent damage to their kidneys.
Other Conditions That Involve the Childhood Nephrotic Syndrome
In about 20 percent of children with the nephrotic syndrome, the kidney biopsy reveals scarring or deposits in the glomeruli. The two most common diseases that damage these tiny filtering units are focal segmental glomerulosclerosis (FSGS) and membranoproliferative glomerulonephritis (MPGN). Very rarely, a child may be born with a condition that causes the nephrotic syndrome (congenital nephropathy).
Since prednisone is less effective in treating these diseases than it is in treating minimal change disease, the doctor may use additional therapies, including cytotoxic agents. Recent experience with a class of drugs called ACE inhibitors (a type of blood pressure drug) indicates that these drugs help prevent protein from leaking into the urine and keep the kidneys from being damaged in children with the nephrotic syndrome.
Hope Through Research
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) conducts and supports research to help many kinds of people with kidney disease, including children. NIDDK’s Division of Kidney, Urologic, and Hematologic Diseases maintains the Pediatric Nephrology Program, which supports research into the causes, treatment, and prevention of kidney diseases in children, including minimal change disease, congenital nephrotic syndrome, primary glomerular disease, and postinfection glomerulonephritis.
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NIH Publication No. 00-4695