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Nephrotic syndrome
Classification and external resources

Histopathological image of diabetic glomerulosclerosis with nephrotic syndrome. H&E stain.
ICD-10 N04.
ICD-9 581.9
DiseasesDB 8905
eMedicine med/1612 ped/1564
MeSH D009404
Not to be confused with nephritic syndrome

Nephrotic syndrome is a nonspecific disorder in which the kidneys are damaged, causing them to leak large amounts of protein[1] (proteinuria at least 3.5 grams per day per 1.73m2 body surface area)[2] from the blood into the urine.

Kidneys affected by nephrotic syndrome have small pores in the podocytes, large enough to permit proteinuria (and subsequently hypoalbuminemia, because some of the protein albumin has gone from the blood to the urine) but not large enough to allow cells through (hence no hematuria). By contrast, in nephritic syndrome, RBCs pass through the pores, causing hematuria.

Contents

Presentation

It is characterized by proteinuria (>3.5g/day), hypoalbuminemia, hyperlipidemia and edema.

Hyperlipidemia is caused by 2 factors:

  • Hypoproteinemia stimulates protein synthesis in the liver, resulting in the overproduction of lipoproteins.
  • Lipid catabolism is decreased due to lower levels of lipoprotein lipase, the main enzyme involved in lipoprotein breakdown.[3]

A few other characteristics seen in nephrotic syndrome are:

Investigations

The following are baseline, essential investigations

Further investigations are indicated if the cause is not clear

Classification and causes

Nephrotic syndrome has many causes and may either be the result of a disease limited to the kidney, called primary nephrotic syndrome, or a condition that affects the kidney and other parts of the body, called secondary nephrotic syndrome.

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Etiologic classification

A broad classification of nephrotic syndrome based on etiology:

 
 
 
Nephrotic
syndrome
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Primary
 
 
 
Secondary

Histologic classification

Nephrotic syndrome is often classified histologically:

 
 
 
 
 
 
 
 
 
 
 
 
Nephrotic syndrome
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
MCD
 
 
 
FSGS
 
 
 
MN
 
 
 
MPGN

Primary causes

Primary causes of nephrotic syndrome are usually described by the histology, i.e., minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS) and membranous nephropathy (MN).

They are considered to be "diagnoses of exclusion", i.e., they are diagnosed only after secondary causes have been excluded.

Secondary causes

Secondary causes of nephrotic syndrome have the same histologic patterns as the primary causes, though may exhibit some differences suggesting a secondary cause, such as inclusion bodies.

They are usually described by the underlying cause.

Secondary causes by histologic pattern

Focal segmental glomerulosclerosis (FSGS)[4]

Minimal change disease (MCD)[4]

Differential diagnosis of gross edema

When someone presents with generalized edema, the following causes should be excluded:

  1. Heart failure: The patient is older, with a history of heart disease. Jugular venous pressure is elevated on examination, might hear heart murmurs. An echocardiogram is the gold standard investigation.
  2. Liver failure: History suggestive of hepatitis/ cirrhosis: alcoholic, IV drug user, some hereditary causes.
    Stigmata of liver disease are seen: jaundice (yellow skin and eyes), dilated veins over umbilicus (caput medusae), scratch marks (due to widespread itching, known as "pruritus"), enlarged spleen, spider angiomata, encephalopathy, bruising, nodular liver
  3. Acute fluid overload in someone with kidney failure: These people are known to have kidney failure, and have either drunk too much or missed their dialysis.
  4. Metastatic cancer: When cancer seeds the lungs or abdomen it causes effusions and fluid accumulation due to obstruction of lymphatics and veins as well as serous exudation.

Diagnosis

Diagnosis is based on blood and urine tests and sometimes imaging of the kidneys, a biopsy of the kidneys, or both.

Treatment

Treatment includes:

General measures (supportive)

  • Monitoring and maintaining euvolemia (the correct amount of fluid in the body):
    • monitoring urine output, BP regularly
    • fluid restrict to 1L
    • diuretics (IV furosemide)
  • Monitoring kidney function:
    • do EUCs daily and calculating GFR
  • Treat hyperlipidemia to prevent further atherosclerosis.
  • Prevent and treat any complications [see below]
  • Albumin infusions are generally not used because their effect lasts only transiently.

Prophylactic anticoagulation may be appropriate in some circumstances.[5]

Specific treatment of underlying cause

  • Standard ISKDC regime for first episode: prednisolone -60 mg/m2/day in 3 divided doses for 4 weeks followed by 40 mg/m2/day in a single dose on every alternate day for 4 weeks.
  • Relapses by prednisolone 2 mg/kg/day till urine becomes negative for protein. Then, 1.5 mg/kg/day for 4 weeks.
  • Achieving stricter blood glucose control if diabetic.
  • Blood pressure control. ACE inhibitors are the drug of choice. Independent of their blood pressure lowering effect, they have been shown to decrease protein loss.

Dietary recommendations

Reduce sodium intake to 1000-2000 milligrams daily. Foods high in sodium include salt used in cooking and at the table, seasoning blends (garlic salt, Adobo, season salt, etc.) canned soups, canned vegetables containing salt, luncheon meats including turkey, ham, bologna, and salami, prepared foods, fast foods, soy sauce, ketchup, and salad dressings. On food labels, compare milligrams of sodium to calories per serving. Sodium should be less than or equal to calories per serving.

Eat a moderate amount of high protein animal food: 3-5 oz per meal (preferably lean cuts of meat, fish, and poultry)

Avoid saturated fats such as butter, cheese, fried foods, fatty cuts of red meat, egg yolks, and poultry skin. Increase unsaturated fat intake, including olive oil, canola oil, peanut butter, avocadoes, fish and nuts. Eat low-fat desserts.

Increase intake of fruits and vegetables. There is no potassium or phosphorus restriction necessary.

Monitor fluid intake, which includes all fluids and foods that are liquid at room temperature. Fluid management in nephrotic syndrome is tenuous, especially during an acute flare.

Complications

  • Venous thrombosis: due to leak of anti-thrombin 3, which helps prevent thrombosis. This often occurs in the renal veins. Treatment is with oral anticoagulants (not heparin as heparin acts via anti-thrombin 3 which is lost in the proteinuria so it will be ineffective.)
  • Infection: due to leakage of immunoglobulins, encapsulated bacteria such as Haemophilus influenzae and Streptococcus pneumoniae can cause infection.
  • Acute renal failure is due to hypovolemia. Despite the excess of fluid in the tissues, there is less fluid in the vasculature. Decreased blood flow to the kidneys causes them to shutdown. Thus it is a tricky task to get rid of excess fluid in the body while maintaining circulatory euvolemia.
  • Growth retardation: does not occur in MCNS.It occurs in cases of relapses or resistance to therapy. Causes of growth retardation are protein deficiency from the loss of protein in urine, anorexia (reduced protein intake), and steroid therapy (catabolism).
  • Microcytic hypochromic anaemia is typical. It is iron-therapy resistant.
  • Hypocalcemia can occur as a result of Nephrotic Syndrome. It may be significant enough to cause Tetany.

Prognosis

The prognosis depends on the cause of nephrotic syndrome. It is usually good in children, because minimal change disease responds very well to steroids and does not cause chronic renal failure. However other causes such as focal segmental glomerulosclerosis frequently lead to end stage renal disease. Factors associated with a poorer prognosis in these cases include level of proteinuria, blood pressure control and kidney function (GFR).

See also

References

  1. ^ nephrotic syndrome at Dorland's Medical Dictionary
  2. ^ "ELECTRONIC LEARNING MODULE for KIDNEY and URINARY TRACT DISEASES". http://www.som.tulane.edu/classware/pathology/medical_pathology/New_for_2001/renal/chap7.html. Retrieved 2008-11-26. 
  3. ^ http://www.hawaii.edu/medicine/pediatrics/pedtext/s13c02.html
  4. ^ a b Fogo AB, Bruijn JA. Cohen AH, Colvin RB, Jennette JC. Fundamentals of Renal Pathology. Springer. ISBN 978-0387-31126-5.
  5. ^ Glassock RJ (August 2007). "Prophylactic anticoagulation in nephrotic syndrome: a clinical conundrum". J. Am. Soc. Nephrol. 18 (8): 2221–5. doi:10.1681/ASN.2006111300. PMID 17599972. http://jasn.asnjournals.org/cgi/pmidlookup?view=long&pmid=17599972. 
  6. ^ Hodson E, Willis N, Craig J (2007). "Corticosteroid therapy for nephrotic syndrome in children". Cochrane database of systematic reviews (Online) (4): CD001533. doi:10.1002/14651858.CD001533.pub4. PMID 17943754. 

External links


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