How is childhood nephrotic syndrome diagnosed?
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 nephrotic syndrome do not have permanent kidney damage.
A strip of chemically treated paper will change color when dipped in urine with too much protein.
In some cases, the doctor may want to examine a small piece of kidney tissue with a microscope to see if something specific is 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. A child who is prone to bleeding problems may require open surgery for the biopsy. General anesthesia will be used if surgery is required. For any biopsy procedure, the child will stay overnight in the hospital to rest and allow the health care team to address quickly any problems that might occur.
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What conditions are associated with childhood nephrotic syndrome?
Minimal Change Disease
The condition most commonly associated with childhood nephrotic syndrome is 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 appearing kidney biopsies. If a 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 the child's health. The doctor may also prescribe another type of drug called a diuretic, which reduces the swelling by helping the child urinate more frequently.
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 experience a relapse, developing 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, the child 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 and chlorambucil. After reducing protein in the urine with prednisone, the doctor may prescribe the cyclophosphamide or chlorambucil for 8 to 12 weeks. Alternatively, cyclosporine, a drug also used in transplant patients, may be given. Treatment with cyclosporine frequently continues over an extended period.
In recent years, doctors have explored the use of mycophenolate mofetil (MMF) instead of cytotoxic agents for children who relapse frequently. MMF is an immunosuppressant used to treat autoimmune diseases and to keep the body from rejecting a transplanted organ. MMF has not been tested for treating minimal change disease in large clinical trials, but doctors report promising results with small numbers of patients. MMF has milder side effects than cytotoxic agents, but taking immunosuppressants can raise the risk of infection and other diseases. The good news is that most children outgrow minimal change disease by their late teens with no permanent damage to their kidneys.
Focal Segmental Glomerulosclerosis (FSGS) and Membranoproliferative Glomerulonephritis (MPGN)
In about 20 percent of children with nephrotic syndrome, a kidney biopsy reveals scarring or deposits in the glomeruli. The two most common diseases that damage these tiny blood-filtering units are FSGS and MPGN.
Because 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 another class of drugs called ACE inhibitors, usually used to treat high blood pressure, indicates these drugs can help decrease the amount of protein leaking into the urine and keep the kidneys from being damaged in children with FSGS or MPGN.
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