Nephrotic syndrome occurs when the kidneys do not work properly and leak large amounts of protein into the urine. It can affect people of any age, but is usually first seen in children aged two to five years old.
Protein lost in the urine results in a lower level of proteins in the blood. This can cause a range of problems, including swelling in the body tissues and a vulnerability to infections (see symptoms of nephrotic syndrome, below).
Symptoms can usually be controlled with medication, especially steroids, and dietary changes (see managing nephrotic syndrome, below).
Children with nephrotic syndrome will have periods when their symptoms are under control (remission) followed by periods when symptoms return (relapses). Most children will relapse less frequently as they get older, eventually "growing out of it" by their late teens.
Children with the usual type of nephrotic syndrome, which responds well to steroid treatment, are not at risk of developing kidney failure.
However, a small proportion of children with congenital (inherited) nephrotic syndrome have a much poorer outcome. They may eventually have kidney failure and need a kidney transplant.
The following information explains:
- the symptoms of nephrotic syndrome
- the causes of nephrotic syndrome
- who is affected
- how it is diagnosed
- managing nephrotic syndrome
Symptoms of nephrotic syndrome
The main symptoms of nephrotic syndrome are summarised below.
Proteins are needed in the blood to help hold water in the blood vessels. When the protein level is very low in nephrotic syndrome, water passes into the tissues and causes swelling (oedema).
Swelling is usually first noticed around the eyes and then around the lower legs and rest of the body.
Specialised proteins called antibodies play an important role in fighting infection. When these are lost from the blood, children are much more likely to get infections and frequently experience fatigue, poor appetite and weakness.
Poor growth and development
The lack of protein – an essential building block of the body – means that children with nephrotic syndrome often have growth and development problems.
Causes of nephrotic syndrome
For about 80% of children with nephrotic syndrome, the cause is unknown. Their kidneys will appear normal or nearly normal after tests are done. Doctors refer to this as "minimal change disease".
Sometimes, nephrotic syndrome can result from a kidney condition or other disease, such as:
Congenital nephrotic syndrome is caused by a faulty gene. Both parents have a healthy copy of the gene and a faulty one, so they do not have nephrotic syndrome themselves, but the affected child will have inherited both faulty genes.
Who is affected?
Nephrotic syndrome can affect people of any age, but is commonly seen in children. It affects more boys than girls. The condition is usually first diagnosed between the ages of two and five years old.
Nephrotic syndrome is rare and affects about 1 in 50,000 children a year. It tends to be more common in families with a history of allergies. In the UK, it is more common in Asian families.
How is it diagnosed?
Nephrotic syndrome can be diagnosed after testing a urine sample with a dipstick (a chemically sensitive strip of paper). The dipstick will pick up large amounts of protein from the urine.
A blood test showing low levels of protein will confirm the diagnosis.
Managing nephrotic syndrome
There is no specific treatment for nephrotic syndrome, but the symptoms can be managed with medication and changes to the diet.
Some children will have relapses and will need to take medication when these occur.
Your child will be referred to a kidney specialist (nephrologist) for investigation of the cause and for specialist treatment.
Your child will normally be prescribed the steroid medicine prednisolone when they are first diagnosed. Prednisolone stops the movement of protein from the blood into the urine.
When prednisolone is prescribed for short periods, there are usually no serious or permanent side effects. Read more about the side effects of prednisolone.
Most children respond to this drug, with protein disappearing from their urine and the swelling going within one to two weeks. This period is known as remission.
Diuretics (water tablets) may also be given to help reduce the fluid build-up. They work by increasing the amount of urine produced.
Penicillin may be prescribed to prevent infection if your child has a lot of swelling, as excess fluid in the tissues provides a good environment for bacteria to grow.
If your child cannot be maintained in remission on a low dose of steroids, or if they have significant side effects, then immunosuppressive medication (usually cyclophosphamide) may be considered instead. Read about the side effects of cyclophosphamide.
Immunosuppressive medications are usually taken to prevent the immune system attacking healthy body tissue. In nephrotic syndrome, they have been shown to control symptoms and reduce risk of relapse.
Your child will need to follow a strict low-salt diet, to prevent further water retention and oedema. This means avoiding processed foods and not adding salt to food. Learn how to cut down on salt.
Your child should also eat plenty of protein-rich foods.
Children with nephrotic syndrome are advised to have the pneumococcal vaccination.
Some children may also be advised to have the varicella (chickenpox) vaccination between relapses.
Live vaccines (such as MMR, varicella and BCG) should not be given while your child is on immunosuppressive medication.
Treating congenital nephrotic syndrome
If your child has congenital nephrotic syndrome, they will need frequent protein supplementation through a drip so they can grow and develop normally. This will often require a prolonged hospital stay.
Sometimes, parents can be trained to administer the protein at home and your child will be regularly reviewed in a clinic, where their blood pressure, growth, weight, kidney function and bone health will be monitored.
It can be difficult for parents to decide which option is best for their child, so you should talk to your doctor about the pros and cons of hospital-based and home-based treatment. Read more about intensive and conservative treatment for congenital nephrotic syndrome.
Children admitted to hospital will be given a continuous infusion of albumin, one of the main proteins lost. This means that a thin plastic tube called a catheter will be inserted into one of the veins in their arm or neck, so albumin can be given straight into the blood. This helps stabilise the protein levels in your child's blood, minimises any swelling and helps your child grow and develop normally.
However, your child will be prone to infections while they have the catheter, and at risk of developing a blood clot in a vein.
To prevent these complications happening, your doctor may recommend removal of one or both of your child's kidneys. This means they will be dependent on dialysis (a machine that replicates kidney function) from an early age until they can receive a kidney transplant.
A person only needs one kidney to survive. Therefore, unlike other types of organ donation, such as heart and liver, a living person can donate a kidney. Ideally, this will be a close relative.
Read more about kidney transplants.