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What is nephrotic syndrome?

Nephrotic syndrome is the name given to a condition where large amounts of protein leak into the urine, causing fluid retention and swelling (oedema) most commonly around the eyes, abdomen, feet and legs.

Causes of nephrotic syndrome

It can occur at any age and is caused by damage to the glomeruli (the tiny filters in the kidney). Normally protein in the blood is too large to pass through the tiny holes in the filters but when the glomeruli are damaged, large amounts of protein can leak through into the urine. This leakage results in low levels of protein in the blood and in fluid retention.

This damage is normally caused by a family of kidney diseases (known collectively as glomerulonephritis). These include:

However, nephrotic syndrome can also occur as a result of:

  • a genetic abnormality (known as congenital nephrotic syndrome)
  • lupus
  • diabetes
  • allergic reactions to medicines
  • infections like Hepatitis B.

When the cause of nephrotic syndrome is not known it is referred to as idiopathic nephrotic syndrome (INS).

The importance of albumin

One key protein (albumin) ensures that fluids are drawn from our body tissues back into our circulating blood. But if albumin is lost from the body extra fluid builds up in the tissues and causes swelling.

Our kidneys control the amount of water in our bodies but when albumin is lost it affects this control and our kidneys then retain more water than normal, adding to the problem.

Nephrotic syndrome symptoms

  • Swelling is the most noticeable symptom – especially around the eyes and face which can be worse first thing in the morning. Later in the day, fluid can collect in the fingers, legs and abdomen which can sometimes make you feel distended. The swelling is soft and will leave a temporary dent if you press on it. Some people can also feel breathless due to excess water around the lungs.
  • Frothy urine can also occur as a result of protein leakage (proteinuria)

Possible complications

Nephrotic syndrome can also make you more susceptible to:

  • blood clots (because proteins that normally help prevent blood clots are lost along with the albumin in the urine)
  • high cholesterol
  • infections.

Nephrotic syndrome diagnosis

Blood and urine tests can easily confirm nephrotic syndrome by showing large amounts of protein in your urine and low levels of protein in your blood, together with a raised blood cholesterol level.

Further blood and urine tests can also gauge your level of kidney function. A kidney biopsy may also be required to confirm the exact cause of your nephrotic syndrome. This is a medical procedure to take small samples of the kidney to look at under the microscope.

Children may also be offered the option of genetic testing in order to see if their nephrotic syndrome is resistant to steroids.

Nephrotic syndrome treatment

Treatments can be given to deal with the symptoms, complications and causes of nephrotic syndrome. These may include:

  • diuretics (water tablets) to reduce water retention
  • dietary advice – e.g. restricting salt and avoiding excessive fluid intake
  • medication called ACE Inhibitors and ARBs to reduce the pressure in the glomeruli and so reduce protein loss
  • anticoagulant treatment to reduce the risk of thrombosis
  • cholesterol-lowering drugs (particularly if the nephrotic syndrome is expected to last a long time)
  • antibiotics, to reduce the risk of infections
  • steroids, to help heal the damage to the glomeruli
  • immunosuppressants (drugs that dampen down the immune system).

Response to treatment varies a lot depending on the underlying cause of the nephrotic syndrome. Some people respond well to one course of treatment with steroids. Others may need repeated courses of treatment. Others may not respond to treatment at all.

If a person does not respond to treatment, after years of heavy protein leakage, the kidneys can eventually fail (this is known as end-stage kidney disease). This can then lead to the need for kidney dialysis or a kidney transplant.

Resources about nephrotic syndrome

If you have been diagnosed with nephrotic syndrome and have any questions or concerns about the condition, don’t hesitate to speak to your kidney specialist or your nurse specialist at your kidney unit.

Reviewed April 2019

Prof Moin Saleem
Professor Moin Saleem, University of Bristol

"We have a potential treatment that could restore kidney function by getting the misfolded protein to the cell membrane where it can do its job”

Professor Moin Saleem

Researcher spotlight

Professors Moin Saleem and Gavin Welsh and their team at Bristol Renal have shown that a drug can restore the function of a protein that is disrupted in the most common form of inherited NS.

More research is now needed, but this work suggests that medications that disrupt the interaction between K8 and misfolded podocin protein could provide a treatment option for patients with the most common inherited form of NS. 

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