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What are Nephrotic Syndrome Kidney Diseases

Nephrotic syndrome glomerular diseases are problems with the kidney that cause protein to spill into the urine. Protein in the urine is called proteinuria. Nephrotic syndromes cause a large proteinuria of more than 3.5 to 4.0 grams of protein lost in the urine each day.

The protein lost in urine during nephrotic syndromes results in a low protein level in the blood. This low blood protein level is called hypoalbuminemia and is defined as a serum albumin of less than 3 grams per 100 ml.

The low protein levels in the blood result in a low colloid osmotic pressure in the blood vessels. The colloid osmotic pressure (also called oncotic pressure) is what normally helps hold fluid inside the blood vessels. When the oncotic pressure is low, fluid leaks out of the blood vessels into the tissue and causes tissue swelling. The swelling of tissues is called edema and may appear as ankle swelling, hand swelling or periorbital edema (swelling around the eyes).

One last additional feature of nephrotic syndrome glomerular diseases is hyperlipidemia. Nephrotic syndromes cause an increased hepatic lipoprotein synthesis resulting in high cholesterol and triglycerides as well. This hyperlipidemia can manifest as lipids in the urine, seen as oval fat bodies on microscopic urinalysis.

Nephrotic syndromes include minimal change disease, membranous glomerulonephritis, diabetic nephropathy, renal amyloidosis, lupus nephropathy and focal segmental glomerulosclerosis.

Minimal change disease:

Minimal change disease is commonly seen in young children under 5 years of age. The cause of inimal change disease is unknown. Fortunately, this kidney disease responds well to treatment with steroids such as prednisone

Membranous nephropathy:

Membranous nephropathy is a form of nephrotic syndrome that commonly occurs after an infection in young adults. In adults age 50 to 60, membranous nephropathy occurs as a symptom of cancer. Unfortunately, steroids are not very effective in treating membranous glomerulonephritis in young adults or older adults.

Diabetic nephropathy:

Diabetic nephropathy is also called diabetic glomerulosclerosis. This form of nephrotic syndrome occurs only in people with diabetes. Diabetic nephropathy creates characteristic kimmel-wilson nodules in the glomerular tufts of the kidney. Diabetic nephropathy usually leads to end stage kidney disease requiring dialysis.

Renal amyloidosis:

The deposition of amyloid fibrils in the kidneys is associated with B cell lymphomas (a form of cancer) and chronic inflammatory states such as rheumatoid arthritis. Renal amyloidosis is a form of nephrotic syndrome that is diagnosed on kidney biopsy using a characteristic congo red stain on microscopy that shows up apple green under polarized light.

Lupus nephropathy:

Systemic lupus erythematosis (SLE) can cause mild to severe kidney problems. There are several different types of lupus nephropathy and the treatment depends on the specific type. Any individual with SLE and signs of renal insufficiency requires a kidney biopsy in order to guide further treatment.

Focal Segmental Glomerulosclerosis:

Focal Segmental Glomerulosclerosis is also called FSGS. It may be idiopathic (unknown cause), superimposed on preexisting kidney problems, associated with loss of kidney mass (as in obesity, sickle cell anemia, cyanotic congenital heart disease) or secondary to other disorders such as heroine abuse, HIV or Parvovirus B19. FSGS appears similar to Minimal Change Disease clinically, but FSGS tends to affect an older population. Additionally, FSGS has a propensity for African-American individuals.

The above nephrotic syndromes, including minimal change disease, membranous glomerulonephritis, diabetic nephropathy, renal amyloidosis, lupus nephropathy and focal segmental glomerulosclerosis, share in common four main characterisitcs. As previously described, any nephrotic syndrome causes proteinuria, hypoalbuminemia, hyperlipidemia and edema.