Nephrotic Syndrome/Kidney Disease

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Nephrotic Syndrome/Kidney Disease

Nephrotic syndrome is kidney disease with proteinuria, hypoalbuminemia, and edema. Nephrotic-range proteinuria is 3 grams per day or more. On a single spot urine collection, it is 2 g of protein per gram of urine creatinine.

There are many specific causes of nephrotic syndrome. These include kidney diseases such as minimal-change nephropathy, focal glomerulosclerosis, and membranous nephropathy. Nephrotic syndrome can also result from systemic diseases that affect other organs in addition to the kidneys, such as diabetes, amyloidosis, and lupus erythematosus.

Nephrotic syndrome may affect adults and children, of both sexes and of any race. It may occur in typical form, or in association with nephritic syndrome. The latter connotes glomerular inflammation, with hematuria and impaired kidney function.
Classification

Nephrotic syndrome can be primary, being a disease specific to the kidneys, or it can be secondary, being a renal manifestation of a systemic general illness. In all cases, injury to glomeruli is an essential feature.

Primary causes of nephrotic syndrome include the following, in approximate order of frequency:

  •     Minimal-change nephropathy
  •     Focal glomerulosclerosis
  •     Membranous nephropathy
  •     Hereditary nephropathies

Secondary causes include the following, again in order of approximate frequency:

  •     Diabetes mellitus
  •     Lupus erythematosus
  •     Amyloidosis and paraproteinemias
  •     Viral infections (eg, hepatitis B, hepatitis C, human immunodeficiency virus [HIV] )
  •     Preeclampsia

Nephrotic-range proteinuria may occur in other kidney diseases, such as IgA nephropathy. In that common glomerular disease, one third of patients may have nephrotic-range proteinuria.[1]

Nephrotic syndrome may occur in persons with sickle cell disease and evolve to renal failure. Membranous nephropathy may complicate bone marrow transplantation, in association with graft versus host disease.

Kidney diseases that affect tubules and interstitium, such as interstitial nephritis, will not cause nephrotic syndrome.

The above causes of nephrotic syndrome are largely those for adults, and this article will concentrate primarily on adult nephrotic syndrome. However, nephrotic syndrome in infancy and childhood is an important entity. For discussion of this topic, see the Medscape Reference article Pediatric Nephrotic Syndrome.

From a therapeutic perspective, nephrotic syndrome may be classified as steroid sensitive, steroid resistant, steroid dependent, or frequently relapsing.

Corticosteroids (prednisone), cyclophosphamide, and cyclosporine are used to induce remission in nephrotic syndrome. Diuretics are used to reduce edema. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers are administered to reduce proteinuria. (See Treatment and Medication.)