Nephrotic Syndrome - Causes, Symptoms and Treatment

Nephrotic syndrome is a kidney disease caused by improper disposal of large amounts of protein in urine. Excessive protein loss in the urine is called proteinuria and can be caused by various diseases, including diabetes mellitus, systemic lupus erythematosus, viral hepatitis and syphilis.

Nephrotic syndrome
Nephrotic syndrome

Definition of proteinuria and nephrotic syndrome

The main role of the kidneys to filter blood. All that is toxic, useless or that is in excess in the bloodstream is usually eliminated in the urine. Proteins are essential substances for our body and therefore do not fit in this group, should not be found in significant amounts in the urine of healthy people.

In people with healthy kidneys, daily urine protein loss is minimal. Considered normal loss of a maximum of 150 mg in 24 hours. Every patient who removes more than this amount has proteinuria. The higher the proteinuria, the more severe renal injury and greater is the risk of the individual developing health problems.

In general, we graduated protein loss in the urine as follows:
  • Proteins in the lowest urine 150 mg per day = Normal.
  • Protein in the urine between 150 mg and 500 mg per day = mild proteinuria.
  • Proteins in urine from 500 mg to 1000 mg per day = mild proteinuria.
  • Protein in the urine of 1000 and 3500 mg per day = moderate proteinuria.
  • Protein in urine above 3500 mg per day = severe proteinuria (proteinuria, nephrotic).

Nephrotic syndrome occurs in patients with severe protein loss above 3500 mg (3.5 grams) per day and it is a sign of disease of the kidney glomeruli.

What is a glomerular disease

The glomerulus is a microscopic structure in the kidney is responsible for filtering the blood. Each glomerulus has a membrane that acts as a filter or a strainer, separating what will be eliminated in the urine and which will remain in the blood. There are about 1 million glomeruli in each kidney. It is as if our kidneys were made up of millions of microscopic filters.

When the glomeruli are healthy, the proteins present in blood are not filtered. The blood entering the kidney has the same amount of protein that blood out of the kidney. This is normal, since proteins are important substances and should not be neglected. However, various diseases which will be mentioned later, can cause injury to the glomeruli, facilitating the onset of proteinuria. The best analogy I can make is with a leaky colander. The protein is a substance of larger size than the pores of the glomerular membrane. In normal situations it does not pass through the filter. However, if the membrane experience a "hole", the proteins can "escape" the same inappropriately being eliminated by the kidneys.

Therefore, closing the concepts:
  • Nephrotic syndrome is a disease that occurs when lose large amounts of protein in the urine (greater than 3500 mg per day).
  • Nephrotic syndrome is a glomerulopathy, that is, a problem that arises due to glomeruli patients.

Symptoms of nephrotic syndrome

Nephrotic syndrome is a set of signs, symptoms and laboratory abnormalities caused by excessive loss of protein in the urine. To have nephrotic syndrome does not just have a proteinuria above 3.5 grams, one must also have symptoms. Therefore, the patient may have nephrotic proteinuria (above 3.5 grams) without presenting nephrotic syndrome.

The most typical sign of proteinuria in excess foaming urine. Generally, the foaming begins to increase when proteinuria is between 500 mg and 1000 mg per day. When the patient has proteinuria in the nephrotic range, the excess foam becomes obvious, causing the patient does not have much doubt that the characteristics of your urine changed.

Excess foam proteinuria in the urine is a sign, not necessarily nephrotic syndrome. The amendments necessary to characterize the nephrotic syndrome are:
  • Edema (swelling), which begin in the legs, but can progress to the whole body, a frame called anasarca.
  • Low blood levels of proteins, mainly albumin is the major protein of blood.
  • Elevated levels cholesterol which occur due to increased production of lipoproteins by the liver in response to levels of the protein drop in the blood.

These three changes described above are those that define the existence of nephrotic syndrome in patients with excessive proteinuria. But the problems do not stop there. The lack of protein in the blood that occurs due to losses in the urine can also cause several other disorders such as:
  • Increased incidence of infection, as antibodies are also a type of protein excreted inappropriately urine.
  • Increased incidence of thrombosis, because some proteins that act preventing blood clotting are also lost in the urine.
  • Malnutrition, loss of essential proteins in the urine.
  • Reduced water volume in the bloodstream, because the lack of protein causes the water present in the blood migrate to outside the vessels toward the tissue and skin. This reduced blood volume is called hypovolemia.
  • Acute renal failure, which can arise due to hypovolemia, or direct injury to the kidney disease that is causing the nephrotic syndrome.

It is worth remarking that the nephrotic syndrome is not a disease in itself, but rather the result of a disease that causes damage to the kidneys. This means that in addition to all these changes directly caused by proteinuria, the patient may still have symptoms of the underlying disease.

Causes of nephrotic syndrome

The cause of nephrotic syndrome are divided into two groups: primary or secondary. Let's start by addressing the secondary causes that are easier to explain.

a) Secondary nephrotic syndrome

Secondary nephrotic syndrome is one that occurs due to a systemic disease also attacks the kidneys. The easiest example to understand is diabetes mellitus. Diabetes is a disease that attacks many organs of the body, including the kidneys. One of the first injury that diabetes causes kidney is slow and progressive aggression glomerular membrane. The patient developed proteinuria, which will worsen over the years and may Chagar to nephrotic range proteinuria.

Other diseases that can also cause kidney damage and nephrotic syndrome are:

b) Primary nephrotic syndrome

The primary nephrotic syndrome is one that occurs by a unique kidney disease, called primary glomerulonephritis.

Primary glomerulopathy which can occur with significant proteinuria and nephrotic syndrome are:
  • Minimal change disease, which is the leading cause of nephrotic syndrome in children.
  • Nephropathy pro IgA.
  • Nephropathy membranous.
  • Glomerulonephritis membranopoliferative.
  • Glomerulosclerosis focal segmental (FSGS).
  • Post-streptococcal glomerulonephritis.

The renal diseases mentioned above usually cause proteinuria, but not when it exceeds the range of 3.5 grams per day, leading to nephrotic syndrome. The presence of significant proteinuria is often a sign of severity of renal injury. Other signs of gravity that may be present, but are not part of nephrotic syndrome in themselves are renal failure and hematuria (blood in the urine).

Diagnosis of nephrotic syndrome

The diagnosis of nephrotic syndrome is done in two steps. The first part consists of the identification of excessive proteinuria. Urine tests as EAS (urinalysis 1) and 24-hour urine are the tests most commonly used to identify and quantify the loss of protein in the urine.

Once identified nephrotic proteinuria, the next step is to diagnose the cause. In patients with diabetes for many years, the cause is obvious and rarely more complex research is needed. In patients previously healthy, with no known diseases, the elucidation of the origin of proteinuria usually take more work. Blood tests such as serology for hepatitis, HIV and syphilis, and autoantibodies research, as FAN, help direct research. In general, however, renal biopsy ends up being necessary for the final diagnosis, especially if the cause is a primary glomerulonephritis.

Treatment of nephrotic syndrome

Treatment of nephrotic syndrome depends on its cause. In patients with hepatitis, syphilis, or HIV, the treatment of these infections generally improves proteinuria.

As diabetes is a disease with no cure, treatment of proteinuria in these cases does not usually have much success. The best results occur in patients who have blood glucose and blood pressure levels controlled.

Drugs such as ACE inhibitors (captopril, enalapril, ramipril, lisinopril, etc.) and antagonists of angiotensin II receptor blockers (losartan, olmesartan, telmisartan, irbesartan, candesartan, etc.) helps to reduce the degree of proteinuria and are indicated in virtually all patients with proteinuria.

In patients with primary glomerulonephritis, treatment is usually done with immunosuppressive drugs such as glucocorticoids, cyclophosphamide, cyclosporine, azathioprine or mycophenolate mofetil. In some cases, the disease respond well to treatment and the patient can see cured after some months. However, not always the result is so good and the progress to ESRD after a few years is relatively common.

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