What is nephrotic syndrome?

Nephrotic syndrome is not a specific disease, but the name given to the set of problems that can arise if the kidneys become damaged.

One of the main jobs of the kidneys is to filter the blood. This allows the body to pass waste products, extra fluid and salts through the urine. The glomeruli are the parts of the kidney where this happens.

With healthy kidneys, proteins in the blood don't usually leak into the urine during the filtering process. But if the glomeruli become damaged, proteins such as albumin can leak into the urine along with the waste products. If too much protein leaks out, that is known as nephrotic syndrome.

What are the symptoms of nephrotic syndrome?

One of the most common symptoms of nephrotic syndrome is fluid retention, which causes puffy eyes, a swollen abdomen and swollen ankles and feet as well as weight gain

Other symptoms can include:

• frothy urine
• extreme tiredness
• infections
• loss of appetite
• anaemia (lack of red blood cells)

Nephrotic syndrome can lead to serious illness such as blood clots and kidney failure.

If you suspect you have nephrotic syndrome symptoms, contact your doctor.

What causes nephrotic syndrome?

Nephrotic syndrome can be caused by diseases that affect the kidneys directly, as well as underlying diseases that affect the whole body.

Kidney diseases that commonly cause nephrotic syndrome include:

• a kidney disease called minimal change disease — this causes a small change in the filters of the kidneys
• focal segmental glomerulosclerosis — this causes scar tissue to build up in the kidneys' filters
• membranous glomerulopathy, also called glomerulous nephropathy — this causes thickening of the lining of the filters
• nephritis, which is inflammation of the kidneys

Some conditions that affect the whole body can cause nephrotic syndrome. These include:

• diabetes mellitus
• lupus multiple myeloma
• some types of cancers
• some infections, such as hepatitis B or malaria

Nephrotic syndrome can also be caused by some medications such anti-inflammatory medicines (NSAIDs) and some cancer medications.

How is nephrotic syndrome diagnosed?

To confirm whether you have nephrotic syndrome, your doctor is likely to:

• assess your symptoms
• take your medical history
• examine you
• ask you to do a series of urine tests, usually over a 24-hour period
• take a blood sample for testing

Some people might need a biopsy of their kidney so the sample can be examined and tested.

How is nephrotic syndrome treated?

If the cause of kidney damage is known, then it will be treated if possible. It will be important to follow the right diet. You might see a dietitian who is likely to recommend a diet with:

• a reasonable amount of protein, but not too much
• not much fat
• very little salt

You might also be advised to restrict how much fluid you drink.

You might also need medicines to manage the symptoms and other issues, such as:

• fluid tablets (diuretics) — to reduce fluid retention
• blood pressure medicine — to reduce pressure in the kidneys’ filters, so that less protein is filtered out’
• cholesterol lowering medication (statins)
• pneumococcal and other vaccinations — if you are at high risk of infection
• anti-clotting medicine — to help thin your blood if there is a risk of blood clots forming
• steroid tablets — which seems to be helpful for minimal change disease