An apparatus (1) for CRRT is provided comprising a blood circuit (10, 20, 30, 60) with a blood removal line (20), a treatment unit (10), and a blood return line (30). A replacement fluid container (78) is configured for containing a medical fluid, a pre-infusion line (70) has a first end (70-1) connected to the replacement fluid container (78) and a second end (70-2) connected to the blood removal line (20) and a blood pump (22) is active on the blood circuit. A replacement fluid pump (72) is active on the pre-infusion line (70), a dialysate circuit (40, 50, 70) comprises an effluent line (50) configured for discharging fluid from the second chamber, and a control unit (80) is connected to the replacement fluid pump (72) and to the blood pump (22) and is configured for performing a rinse-back procedure for restituting blood to a patient. The rinse-back procedure comprises conveying blood contained in the blood circuit (10, 20, 30, 60) towards the second end (30-2) of the blood return line (30) using the medical fluid.
