Pediatric Nephrotic syndrome is defined by the presence of:
- nephrotic proteinuria > 1 g/m2/day,
- hypoproteinemia - albumin usually < 25 g/l, based on protein loss to urine,
- hypercholesterolemia - based on increased lipoprotein synthesis (caused by hypoproteinemia),
- edema - based on increased naturism resorption in tubules.
Nephrotic syndrome is a constellation of clinical findings that is the result of massive renal losses of protein. Thus, nephrotic syndrome is not a disease itself, but the manifestation of many different glomerular diseases.
Minimal Change Disease
Minimal Change Disease (also known as lipoid nephrosis) is a disease of thekidney that causes nephrotic syndrome and usually affects children (peak incidence at 2–3 years of age).
Nephrotic syndrome is a nonspecific disorder in which thekidneys are damaged, causing them to leak large amounts of protein 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.
NS is believed to have an immune pathogenesis. Evidence of the immune-mediated nature of NS is demonstrated by the fact that immunosuppressive agents, such as corticosteroids and alkylating agents, can result in remission of nephrotic syndrome.
Pathology of Edema in Nephrotic Syndrome
The classical explanation for edema formation is a decrease in plasma oncotic pressure, as a consequence of low serum albumin levels, causing an extravasation of plasma water into the interstitial space. The resulting contraction in plasma volume (PV) leads to stimulation of the renin-angiotensin-aldosterone axis and antidiuretic hormone. The resultant retention of sodium and water by the renal tubules contributes to the extension and maintenance of edema.
A more recent theory of edema formation posits that massive proteinuria leads to tubulointerstitial inflammation and release of local vasoconstrictors and inhibition of vasodilation. This leads to a reduction in single-nephron glomerular filtration rate and sodium and water retention.
Patients with nephrotic syndrome are at increased risk for thrombosis.
Various factors play a role in the increased incidence of thrombosis. Abnormalities described in INS include the following: