Kidneys - nephrotic syndrome

How your kidneys work

The kidneys are two large bean-shaped organs located in your lower back.

Each kidney contains up to one million nephrons, the filtering units of your kidneys. Inside a nephron, there is a tiny set of blood vessels called the glomerulus. The glomerulus filters your blood allowing excess fluid and waste to be removed in your urine.

What is nephritis?

Nephrotic syndrome is a condition of the kidneys. It is usually caused by one of the diseases that damage the kidneys’ filtering system. This allows a protein called albumin to be filtered out into the urine (albuminuria).

When the protein level in the blood drops, liquid seeps out of the smallest blood vessels (capillaries) all over the body and settles into the surrounding tissue, causing fluid swelling (oedema). Treatment includes medications and dietary changes.

What are the different types of nephritis?

There are many different types of nephritis. It can vary from a mild, non-damaging condition to a serious problem causing kidney failure. Some types of nephritis appear mild at first but can later cause high blood pressure or become more serious.

Nephritis is often described as acute or chronic. The acute form develops suddenly, sometimes after a throat or skin infection. These infections may need treatment such as antibiotics.

Chronic nephritis develops silently over several years and can lead to kidney failure. Sometimes an acute attack can cause chronic nephritis years later.

Causes of nephrotic syndrome

Some of the causes of nephrotic syndrome include:

• changes to the immune system (minimal change disease or lipoid nephrosis) – nephrotic syndrome due to changes to the immune system is most common in children. It is called ‘minimal change disease’ because the kidney filters appear normal under a microscope. The cause is thought to be changes in certain cells of the immune system. The function of the kidneys is normal and the outlook for recovery is usually excellent
• inflammation – local inflammation or swelling damages and scars the kidney filters. Examples of this are focal segmental glomerulosclerosis and membranous nephropathy. Treatment may not resolve the condition, and the kidneys may gradually lose their ability to filter wastes and excess water from the blood
• other health conditions, which can lead to ‘secondary nephrotic syndrome’ – this can be caused by certain conditions including diabetes, drugs, cancer and systemic lupus erythematosus (SLE).

Symptoms of nephrotic syndrome

The symptoms of nephrotic syndrome include:

• foamy and frothy urine
• unexplained weight loss
• general malaise (feeling unwell)
• oedema (fluid retention or swelling), particularly around the abdomen (belly area), legs and eyes
• muscle wasting
• stomach pain
• dizziness when standing up from a lying or sitting position (orthostatic hypotension).
• loss of appetite
• fatigue

Complications of nephrotic syndrome

Complications of nephrotic syndrome can include:

• dehydration – low protein levels may lead to a reduction in blood volume. In severe cases, intravenous fluids may be given to boost the body’s water content
• blood clots – these occur in the leg veins and occasionally in the kidney veins. Blood clots can also go into the lungs and cause chest pain, breathlessness or coughing up of blood
• infection – infection and inflammation (peritonitis) of the peritoneal cavity. This is the thin elastic lining that contains the pancreas, stomach, intestines, liver, gallbladder and other organs. A fever may indicate infection
• kidney failure – without treatment, the kidneys may fail in extreme cases
• high blood pressure
• anaemia.

Diagnosis of nephrotic syndrome

Diagnosing nephrotic syndrome involves a number of tests, including:

• urine tests – excessive protein makes the urine appear frothy and foamy. A test for albumin/creatinine ratio may be done to measure the amount of albumin in the urine in relation to the amount of creatinine
• blood tests – these estimate the glomerular filtration rate (eGFR), which shows how well the kidneys are working

Sometime further tests are needed:

• kidney biopsy - A needle is passed through your skin into the kidney to remove a small piece of kidney tissue to be checked under a microscope.
• ultrasound - An instrument is moved over the skin, sending and receiving signals to make pictures of your organs, including kidneys and bladder.
• computerised Tomography (CT) Scan or Magnetic Resonance Imaging (MRI) - Radio-frequency wavelengths and a strong magnetic field are used to provide clear and
  detailed pictures

Treatment for nephrotic syndrome

There are many types of nephritis and the treatment will depend on which type of nephritis you have. Many types of nephritis require observation but no treatment, and rarely lead to long-term kidney damage.

Control of high blood pressure is the most important treatment for nephritis. Your doctor may prescribe medications to reduce your blood pressure and help to protect your kidney function. Fish oil supplements may help to reduce inflammation, and a diuretic (to remove excess water and reduce swelling) may also be suggested.

Talking to your kidney specialist (nephrologist) will help decide whether these are useful treatment options for you. New treatments are being tested to see if it can help to slow down kidney failure.

Where to get help

• Your GP (doctor)
• Kidney specialist (nephrologist)
• Kidney Health Australia helpline Tel. 1800 454 363
• Kidney Health Australia - Focal Segmental Glomerulosclerosis factsheet