The syndrome is characterised by abnormally high levels of protein in the urine (particularly one called albumin) and abnormally low protein levels in the blood. This often leads to fluid retention in the body tissues causing swelling (oedema) and can be associated with high blood cholesterol levels and high blood pressure.
The glomeruli act as filters to remove waste products from the blood, which are then excreted from the body in the urine. In nephrotic syndrome these filters become defective and leak, allowing large quantities of protein to be lost in the urine. Protein in the blood acts to prevent water entering the body’s cells. Reduced blood protein levels cause water to leak into body tissue, causing swelling.
The three most common forms of glomerulonephritis causing nephrotic syndrome are:
- Minimal change nephropathy (also called minimal change disease).
- Membranous glomerulonephritis.
- Focal segmental glomerulonephritis.
A wide range of other disorders (including amyloidosis, diabetes, and systemic lupus erythematosus) and factors such as exposure to toxins are less common causes of the nephrotic syndrome.
In children, nephrotic syndrome is normally detected between the age of 3 and 4 years old. Most children have the form of glomerulonephritis called minimal change nephropathy. This is where minimal or no glomerular abnormalities are noted by a microscope. This form of nephrotic syndrome affects approximately 1 in 50,000 children. It can usually be successfully treated.
In adults, membranous glomerulonephritis and focal segmental glomerulonephritis are the most common causes of the nephrotic syndrome.
Signs and symptoms
Signs and symptoms include:
- Foamy urine
- Fatigue and weakness
- Swelling, especially around the eyes, hands, feet, and abdomen
- Loss of appetite
- Increased weight from fluid retention
- High protein levels in the urine and low protein levels in the blood.
As the condition progresses there may be:
- Susceptibility to infectious diseases due to an impaired immune system
- An increased risk of blood clots (thrombosis)
- Muscle wasting (due to the loss of protein)
- Weakening of the bones
- Abnormally low or abnormally high blood pressure
- High blood cholesterol levels
- Kidney failure.
A kidney biopsy is where a tiny piece of kidney is removed by a needle and studied under a microscope. This procedure usually involves a one-day stay in hospital and is performed under a light general anaesthetic or a local anaesthetic. Ultrasound scanning of the kidneys may also be performed.
Medications that reduce the inflammatory effects of the immune system on the glomeruli are the mainstay of treatment. Medications to achieve this include corticosteroids (eg: prednisone) and potent immune-suppressing medications.
Medications to reduce high blood pressure and high blood cholesterol levels may also be prescribed. Blood-thinning medications (anticoagulants) may be prescribed to reduce the risk of developing blood clots.
The doctor may also recommend restricting fluid intake or may prescribe medications that increase the amount of urine produced (diuretics). These, along with bed rest, will help to reduce swelling.
The doctor or a dietitian may recommend a special diet aimed at controlling levels of protein, salt, and cholesterol in the body. Overall, it is important to maintain good health and nutrition and to ensure other medical conditions are treated promptly.
Further information and support
Kidney Health New Zealand
Freephone: 0800 543 639 (0800 Kidney)
Kidney Health New Zealand (2008). Nephrotic syndrome in children: What is nephrotic syndrome? (Information Sheet). Christchurch: Kidney Health New Zealand. https://www.kidneys.co.nz/resources/file/nephrotic_syndrome_in_children_03.pdf
Mayo Clinic (2020). Nephrotic syndrome (Web Page). Rochester, MN: Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/nephrotic-syndrome/symptoms-causes/syc-20375608 [Accessed: 25/11/20]
O’Toole, M.T. (Ed.) (2017). Nephrotic syndrome. Mosby’s Dictionary of Medicine, Nursing & Health Professions (10th ed.). St Louis, MO: Elsevier.
Last Reviewed: December 2020