Nephrotic Syndrome

Nephrotic Syndrome

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Definition

Nephrotic syndrome is a disorder caused by damage to the small blood vessels in your kidneys that filter waste and excess water from your blood. When healthy, these small blood vessels keep blood protein from seeping into your urine and out of your body. When damaged, they don't perform this function effectively, and protein can leak out of your blood and lead to swelling (edema).

Signs and Symptoms

Symptoms

* Swelling (edema), particularly around your eyes and in your ankles and feet

* Foam in the toilet water, which may be caused by excess protein in your urine

* Weight gain due to excess fluid retention

* Loss of appetite

* Vomiting

Signs

* High levels of protein in your urine (proteinuria)

* Low levels of the blood protein albumin (hypoalbuminemia)

* Elevated blood levels of cholesterol and triglycerides

* Swelling (edema)

Causes

Nephrotic syndrome is caused by damage to the tiny blood vessels (glomeruli) of your kidneys.

Healthy glomeruli keep blood protein (mainly albumin) — which is needed to maintain the right amount of fluid in your body — from seeping into your urine. When damaged, glomeruli often lose this ability.

Many possible causes

Many disorders can cause glomerular damage and lead to nephrotic syndrome. The following medical conditions account for most cases of nephrotic syndrome:

1. Minimal change disease. The most common cause of nephrotic syndrome in children, this disorder results in abnormal kidney function, but when the kidney tissue is examined under a light microscope, it appears normal or nearly normal. The cause of the abnormal function typically can't be determined.

2. Focal segmental glomerulosclerosis. Characterized by scattered scarring of some of the glomeruli, this condition may result from another disease, a genetic defect or occur for no known reason.

3. Membranous nephropathy. This kidney disorder is the result of thickening membranes within the glomeruli. The exact cause of the thickening isn't known, but it's sometimes associated with other medical conditions, such as hepatitis B, malaria, lupus and cancer.

4. Diabetic kidney disease. Diabetes can lead to kidney damage (diabetic nephropathy) that affects the glomeruli, particularly in people with diabetes that's poorly controlled or people who have high blood pressure.

5. Systemic lupus erythematosus. This chronic inflammatory disease can lead to serious kidney damage.

6. Amyloidosis. This disorder occurs when substances called amyloid proteins accumulate in your organs. Amyloid buildup often affects the kidneys, damaging their filtering system.

Tests and diagnosis

* Urine tests. A urinalysis will show large amounts of protein in your urine if you have nephrotic syndrome. Fats also may be present in your urine.

* Blood tests. If you have nephrotic syndrome, a blood test may show low levels of the protein albumin (hypoalbuminemia) specifically and decreased levels of blood protein overall. Loss of blood protein may cause an increase in blood cholesterol and blood triglycerides. Serum creatinine and blood urea also may be measured to assess your overall kidney function.

* Kidney biopsy. A kidney biopsy may be necessary to confirm a diagnosis of the renal cause of nephrotic syndrome. This procedure involves using a special biopsy needle to extract small pieces of kidney tissue under local anesthesia for microscopic examination to search for glomeruli damage. Sometimes special stains of the kidney tissue or special studies, such as electron microscopy, also are necessary for diagnosis. If so, tissue diagnosis may take longer.