INTRODUCTION: Acute kidney injury (AKI) is common in critically ill neonates, including very and extremely low birth weight (VLBW, ELBW) neonates. In severe cases, kidney replacement therapy (KRT) may be warranted. Currently, available KRT devices are only indicated for those weighing ≥ 2.5 kg and require a double lumen or 2 separate single lumen catheters. We miniaturized the Kirpa Kit manual dialysis device, naming it the Brophy Kit, and we assessed its METHODS: We diluted packed red blood cells to a normal hematocrit (Hct: 31.1%-36.8%) and conducted 12 clearance and 3 UF experiments. A cycle consisted of aspirating 10 ml of blood from the blood bag, passing it through a hemofilter, and returning it in a circular path. For clearance experiments, we tested 4 configurations, with varied timing and volume of saline flushes to refresh the dialysis compartment, then measured blood urea nitrogen (BUN) and potassium concentrations every 5 cycles. For each UF cycle, 1 ml of ultrafiltrate was removed, and Hct was measured every 10 cycles. RESULTS: Median BUN and potassium reduction were 31.0% (interquartile range [IQR]: 17.6-37.9) and 35.0% (IQR: 26.9-41.7), respectively, after 30 clearance cycles. Median Hct increased to 52.6% (IQR: 52.5-53.8) after 60 UF cycles, more than the expected Hct (47.7%). CONCLUSION: The Brophy Kit performs