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Updated September 01, 2015.

WHAT IS NEPHROTIC SYNDROME 

Nephrotic syndrome is a combination of certain clinical findings that can be seen in patients with kidney disease.  It is therefore a clinical diagnosis and not a disease by itself. It can be seen in a variety of conditions that lead to it. The combination of abnormalities that are grouped together under the umbrella term nephrotic syndrome include:

• Severe proteinuria, or loss of an abnormally high level of protein in the urine

• Low protein level in the blood
• Edema/swelling in the body
• High cholesterol level in the blood
• Possible tendency to form blood clots

HOW DOES NEPHROTIC SYNDROME DEVELOP

Alteration in the kidneys' filter (called the glomerulus) can lead to nephrotic syndrome.  These alterations can occur on their own with no apparent explanation, but are most commonly seen because of damage to the kidneys' filter from other diseases that I mention below.  Regardless of the cause, alterations in the kidneys filter's structure lead to abnormalities in its function.  

Typically the kidneys filter is set up in such a way that it only allows certain substances/toxins out from the blood into the urine.  It holds back on bigger molecules like protein particles found in the blood (one of which is albumin).  In nephrotic syndrome, the filter loses its ability to discriminate between the substances that pass through it, and even larger molecules like protein begin to leak out into the urine. This sets off a cascade of events that lead to full-fledged nephrotic syndrome.

 In a way, the good stuff passes out in to the urine with the bad, and the body begins to "throw the baby out with the bathwater".

WHAT DISEASES AFFECTING THE KIDNEY CAUSE NEPHROTIC SYNDROME

Nephrotic syndrome can occur in a variety of conditions.  However sometimes no cause might be identified.  Some of the common known diseases that cause alterations leading to nephrotic syndrome include:

• Diabetes mellitus
• Certain medications like bisphosphonates (used to treat osteoporosis), NSAID painkillers, and more
• Autoimmune diseases like lupus
• It can occur in parallel with certain cancers
• Chronic infections through indirect immune mechanisms can sometimes lead to nephrotic syndrome. HIV is a common example
• Certain environmental toxins

HOW DO YOU DIAGNOSE NEPHROTIC SYNDROME 

As mentioned above, the diagnosis of nephrotic syndrome involves appreciating the constellation of findings that make nephrotic syndrome.  Usually the suspicion is set off in a patient with otherwise no other reason for swelling around the eyes or in the ankles.  Investigations for this would often include urine testing.  This would then reveal severe loss of protein in the urine.  Sometimes patients with severely elevated protein loss in the urine will complain of seeing foam or suds in urine.  Other abnormalities like low protein level in the blood or high cholesterol levels may also be noted on lab tests.

All of the above tests will however not necessarily identify the cause of nephrotic syndrome.  If the cause is not apparent on clinical history, a kidney biopsy will often need to be done to figure out the specific disease causing the nephrotic syndrome.

WHAT ARE THE COMPLICATIONS OF NEPHROTIC SYNDROME 

Nephrotic syndrome due to certain diseases may actually resolve on its own.  However uncorrected nephrotic syndrome can have harmful consequences.  

• The most obvious one is progressive worsening of the kidneys' function, and its ability to filter waste products and excess fluid from the body.  
• High cholesterol levels seen in nephrotic syndrome will increase the risk of cardiovascular disease.
• Patient also have a higher risk of forming blood clots and can see entities like deep vein thrombosis and pulmonary embolism develop.  
• An increased risk of infections is seen due to loss of protective antibodies (which are also proteins) into the urine.

?IS NEPHROTIC SYNDROME TREATABLE? HOW DO YOU TREAT NEPHROTIC SYNDROME

In order to treat nephrotic syndrome, you first need to figure out why you have nephrotic syndrome.  If the reason is not apparent on the clinical history alone, a kidney biopsy will be necessary to answer this question.  Once a specific cause is identified, treatment might include a combination of different medications ranging from renin-angiotensin blocking blood pressure medications (called ACE inhibitors or angiotensin receptor blockers), to steroids, to other immunosuppressant medications (like cyclosporine), etc. This is a condition that is best treated by seeking the advice of a specialist nephrologist.  

Remember, the outcome of successful treatment again will depend on the cause.  Certain entities are more likely to be responsive to treatment, while others will not even respond to the biggest gun out there.

The specific treatment also needs to be combined with a focus on treating the complications that would've developed.  Hence water pills like furosemide might be necessary to treat severe swelling that is often seen.  Blood thinners may be required for some patients to prevent blood clots.  A low-sodium diet is almost always necessary.