Reassessing the role of kidney biopsy in early idiopathic steroid-resistant nephrotic syndrome among children and young adults.

backgroundAbout 90% of cases with idiopathic nephrotic syndrome (NS) respond to corticosteroids. The remaining 10%, classified as steroid-resistant nephrotic syndrome (SRNS), typically undergo a kidney biopsy before receiving additional immunosuppression. This study examined the extent to which kidney biopsy findings influenced management in children and young adults with newly diagnosed idiopathic SRNS.

methodsWe conducted a retrospective chart review of patients aged 1-21 years and diagnosed with SRNS at the Detroit Medical Center from January 2000 to December 2024. Exclusion criteria were patients with syndromic diagnoses and presentation with gross hematuria, hypertension, or identifiable systemic disease.

resultsThe study included 55 patients, 46 underwent kidney biopsy after the diagnosis of SRNS (mean age 10.9 ± 4.6 years), and 9 had elective biopsies based on age before being diagnosed with SRNS (mean age 16 ± 1.7 years). Biopsy diagnoses included focal segmental glomerulosclerosis (72%), minimal change disease (24%), and membranous nephropathy (4%). Sixty-five percent of cases had mild to moderate interstitial fibrosis/tubular atrophy. Most patients (84%) were admitted overnight, 71% had flank or back pain, and 15% had a hematoma. Post-biopsy, 96% of patients received calcineurin inhibitors (CNIs): cyclosporine (n = 38) or tacrolimus (n = 15). At one year, 96% remained on CNIs.

conclusionsKidney biopsy did not significantly alter immunosuppressive management in newly diagnosed patients with SRNS at our center. Larger multicenter studies are needed to confirm these findings and evaluate whether more selective biopsy criteria could spare patients from a potentially avoidable invasive procedure, improve clinical management, and reduce healthcare costs.