More than 80% of children with idiopathic nephrotic syndrome
will respond to steroid therapy by entering complete
remission. Based on this statistic, an initial trial of 4 to 8
weeks of high-dose daily steroid therapy is usually prescribed
in children under 10 before considering renal biopsy. In
general, renal biopsy is indicated only in the setting of atypical
features such as (1) age at onset (less than 1 year or more
than 10), (2) SDNS or SRNS, (3) gross or persistent microscopic
hematuria or presence of red cell casts, (4) abnormal
serologies, or (5) signifi cant persistent renal failure. Due to
the known nephrotoxicity (interstitial fi brosis) of calcineurin
inhibitors such as cyclosporine and tacrolimus, renal biopsy
is also indicated before initiation of these second-line or
third-line immunosuppressive agents, as well as approximately
every 2 years as long as use of these medications
continues