Renal replacement therapy in patients with acute kidney injury due to cast nephropathy: benefits of PMMA filters

Introduction: Acute kidney injury (AKI) due to cast nephropathy in multiple myeloma (MM) carries high morbidity and mortality.Objective: To reduce free light chains (FLC), extracorporeal therapies are used as adjuncts to chemotherapy.Hemodialysis (HD) with polymethylmethacrylate (PMMA) membranes may provide FLC removal with minimal albumin loss, representing a viable option for these patients.Material and methods: Single-center, retrospective observational study.We included MM patients with KDIGO stage-3 AKI treated between June 2019 and December 2023 with intensive HD using PMMA BK-2.1F as an adjunct to chemotherapy.We assessed FLC trajectory, renal function, and survival.Results: 13 patients were analyzed.At treatment completion, 61.5% achieved dialysis independence and some degree of renal response.Glomerular filtration rate increased by 20.37 mL/min/1.73m² at completion (p < 0.001) and 35.92 mL/min/1.73m² at 12 months (p < 0.001).Twelve-month mortality was 38.5% (5/13), concentrated among patients without renal response (trend, p = 0.083).Conclusions: In patients with MM and KDIGO stage-3 AKI, intensive HD with PMMA as an adjunct is associated with a high rate of dialysis independence, sustained glomerular filtration rate improvement, and survival.Given the small sample and limited per-session measurement, larger comparative studies are needed to confirm effectiveness and define its role versus other modalities.