505 - Clinical Relevance of Kidney Biopsy in Steroid-Resistant Nephrotic Syndrome in Children and Young Adults

Publication Number: 2491.505

Nikesh Thadani, Wayne State University School of Medicine, Detroit, MI, United States; Wael M. Abukwaik, Children Hospital of Michigan, Detroit, MI, United States; Tej K.. Mattoo, Wayne State University School Of Medicine, Troy, MI, United States

Background: Idiopathic nephrotic syndrome (NS) is one of the most common kidney disorders in children, with ~90% responding to corticosteroid therapy. The remaining 10%, classified as steroid-resistant nephrotic syndrome (SRNS), undergo a kidney biopsy before receiving additional immunosuppression.

Objective: To assess the clinical significance of kidney biopsy in guiding the immunosuppression management of newly diagnosed children with SRNS.

Design/Methods: We conducted a retrospective chart review of children and young adults diagnosed with SRNS at the Detroit Medical Center between January 2000 and November 2023. Patients with a diagnosis of idiopathic early steroid-resistant nephrotic syndrome between the ages of 1 and 21 years were included in the study. Exclusion criteria included syndromic patients, infantile nephrotic syndrome, and the presence of gross hematuria, hypertension, or any identifiable systemic disease at the time of initial diagnosis.

Results: Forty-six patients (21 males, 25 females; mean age 10 ± 4.5 years) were included in the study. The mean duration of corticosteroid therapy before biopsy was 5.2 ± 1.3 weeks. The kidney biopsy showed focal segmental glomerulosclerosis in 33 (72%), minimal change disease in 11 (24%), and membranous nephropathy in 2 (4%) patients. Interstitial fibrosis and tubular atrophy were graded as normal in 33%, mild in 60%, and moderate in 8% of biopsy reports. Most patients (89%) required an overnight hospital stay. Biopsy-related complications included flank or back pain in 72% and hematoma in 11%. Post-biopsy, 96% of patients received calcineurin inhibitors (CNIs): cyclosporine (n=34) or tacrolimus (n=10). At one year, 96% remained on CNIs (24 on cyclosporine, 19 on tacrolimus). Two patients remained on mycophenolate mofetil throughout, and one discontinued therapy due to tacrolimus resistance.

Among the two patients with membranous nephropathy, one (PLA2R-positive) had a history of thromboembolic events and was treated with mycophenolate mofetil, while the other (PLA2R-negative, negative secondary workup) received tacrolimus. Both were initially classified as idiopathic SRNS.

Conclusion(s): Kidney biopsy did not significantly alter immediate post-biopsy immunosuppression management in our newly diagnosed patients with SRNS. A larger study is needed to validate our observations and to explore whether more selective biopsy criteria could spare patients from a potentially avoidable invasive procedure, improve clinical management, and reduce healthcare costs.