Kidney diseases

Nephrotic syndrome

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Nephrotic syndrome
portrait of Fernando Martínez Sáez
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Fernando Martínez Sáez
Medically reviewed by our Medical staff

Last update: 20-10-2021

How else can it be called?

  • Nephrosis

  • CIE-10: N04

What is nephrotic syndrome?

Nephrotic syndrome is a kidney disorder where the glomeruli become damaged, allowing an excessive excretion of proteins into the urine.

Nephrotic syndrome is a consequence of the inflammation of the membrane tissue in the glomeruli of the kidney. The inflammation alter the glomerular filtration, leading to an increased leakage of protein into the urine.

The glomeruli (a single one is called a glomerulus) are tiny blood vessels located inside the kidneys where the blood is filtered. In each kidney, there are around 800,000 to 1 million glomeruli. Glomeruli allow a certain amount of water and waste products to leave the blood through the urine. Normally, proteins are unable to pass through the glomerular filter. However, when the glomeruli are damaged, as seen in nephrotic syndrome, large amounts of proteins leave the blood circulation and pass to the urine.

Nephrotic syndrome leads to a high level of proteins in the urine and a low level of proteins in the bloodstream. Cholesterol in the blood is also high and as a result of the lack of proteins in the blood, edema (swelling) is present.

What are the main causes of nephrotic syndrome?

In children, the most common cause is minimal change disease or MCD (80% of cases in children). In adults, membranous glomerulonephritis (membranous nephropathy) is the most common cause (30-40% of cases in adults).

Other kidney disorders that may cause nephrotic syndrome include:

  • Focal segmental glomerulosclerosis
  • Membranoproliferative or mesangiocapillary glomerulonephritis

Secondary causes of nephrotic syndrome include:

What incidence does it have?

People who suffer from nephrotic syndrome are from all age groups, but it is more common in children between the ages of 18 months and 4 years.

People who suffer from nephrotic syndrome are from all age groups, but it is more common in children between the ages of 18 months and 4 years.

In children, boys are more frequently affected than girls are; in adults, the ratio male to female is closer to equal.

What are the main symptoms of nephrotic syndrome?

The main symptoms of nephrotic syndrome are:

  • Edema (swelling) in the face, eyelids, ankles, etc.
  • Swollen (distended) abdomen.
  • Foamy urine.
  • Weight gain as parts of the body become swollen with fluid (water retention).
  • Decreased appetite.
  • High blood pressure.
  • Fatigue and weakness.
  • Muscle wasting.

How can it be diagnosed?

Nephrotic syndrome is specifically defined by the presence of:

  • Proteinuria (increased levels of protein in the urine)
  • Hypoalbuminemia (decreased levels of albumin in the blood)
  • Edema (swelling)

On a physical exam, edema (swelling) is usually present. Edema is the accumulation of fluid in the interstitial compartment of tissues within the body and it is a sign of the dilution of the interstitial protein concentration.

The urinalysis will reveal significant quantities of protein (more than 3.5 grams per day), and the presence of hyaline casts.

The blood test will reveal hypoalbuminemia (low albumin level <3 g/dl). Cholesterol (LDL cholesterol) and triglycerides will also be increased.

As a result of the previous tests, nephrotic syndrome can be diagnosed. To find the underlying cause there are several screening tests available:

  • Antinuclear antibody test (ANA).
  • Rheumatoid factor test (RF).
  • Cryoglobulins.
  • Glucose tolerance test
  • Complement blood test.
  • Hepatitis B and C antibodies.
  • VDRL test (syphilis screening).
  • Serum protein electrophoresis (SPEP).
  • Kidney (renal) biopsy.

What is the recommended treatment?

To avoid a progressive deterioration of renal function is necessary to know the underlying cause in order to apply the proper treatment. Treating the underlying condition will often improve the symptoms of nephrotic syndrome as well.

The following drugs may be administered depending on the underlying cause:

  • Corticosteroids (prednisone)
  • Immunosuppressants (cyclophosphamide)
  • Antihypertensive drugs
  • Diuretics
  • Angiotensin-converting enzyme (ACE) inhibitors. ACE can reduce the loss of protein in the urine

Treatment with medication to lower cholesterol and triglyceride levels are often associated.

Anticoagulants may be prescribed if there is a risk of clot formation.

In addition, a moderate-protein diet (1 g of protein per kilogram per day) is recommended.

Salt (sodium) should be restricted to reduce inflammation and edema.

Vitamin D intake is recommended when the nephrotic syndrome is chronic and does not respond to the treatment.

What is the prognosis of the disease?

Nephrotic syndrome can be acute and transitory as a consequence of, for example, an infection. In other cases, nephrotic syndrome may be chronic and lifelong treatment will be required.

When the kidney disorder is caused by the minimal change disease, the prognosis is very favorable with more than 90% of all patients responding to treatment. When nephrotic syndrome is caused by an infection, an allergic reaction, or a drug-induced reaction, the prognosis is also favorable.

What complications may exist?

The main complications related to nephrotic syndrome are:

  • Acute renal failure
  • Chronic renal failure
  • Atherosclerosis and coronary heart disease
  • Renal vein thrombosis
  • Infections
  • Malnutrition
  • Fluid overload
  • Congestive heart failure
  • Pulmonary edema
Medically reviewed by our Medical staff on 20-10-2021

Bibliography

  • First Aid for the Basic Sciences: Organ Systems (3rd Ed) 2017, Tao Le, William L. Hwang, Vinayak Muralidhar, Jared A. White and M. Scott Moore, ISBN: 978-1-25-958704-7, Pag. 623.
  • Manual of Clinical & Practical Medicine. G.S. Sainani, V.R. Joshi, Rajesh G. Sainani. 2010. Pag 388. ISBN: 978-81-312-2313-0.
  • Essential of Clinical Inmunology. Helen Chapel, Mansel Haeney, Siraj Misbah, Neil Snowden. 6th edition. Pag 186. ISBN 978-1-118-47295-8.
  • Nephrotic syndrome. Information for parents and carers about children’s kidney condition. Available on: https://www.infokid.org.uk

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