Role of a kidney biopsy in nephrotic syndrome
What is the role of a kidney biopsy in the assessment of patients with nephrotic syndrome?
A kidney biopsy is necessary to definitively distinguish between the four causes of primary nephrotic syndrome.
There are differences in the application of kidney biopsy in pediatric and adult patients.
• In children, the criteria for performing a kidney biopsy prior to treatment are:
• Age below 6 months
• Onset in adolescence; that is, Tanner stage 3 or greater
• Low C3 level
• Any unusual clinical feature
• Otherwise, most pediatric nephrologists defer a kidney biopsy until after completion and resistance to steroids. The rationale for this approach is the high frequency of MCNS in children with new-onset nephrotic syndrome. Importantly, a standard course of steroids will not modify the underlying renal histopathology if there is a lesion other than MCNS.
• In adults with nephrotic syndrome, a kidney biopsy is done prior to therapy because of diverse potential pathology and reduced tolerance of corticosteroids. The tissue sample should be processed for light microscopy, immunofluorescence, and electron microscopy to establish the diagnosis.
• Special stains for glomerular proteins, such as synaptopodin and dystroglycan, may help discriminate among the causes of primary nephrotic syndrome. These are podocyte-associated proteins whose expression has been shown to be different in patients with MCNS versus FSGS.
