A system for treating, and its associated method of using, a hemorrhagic fluid previously removed from a patient for autotransfusion, including a hemorrhagic fluid processing unit (100), said processing unit. (100) comprising: - a filtration device (110) for tangential filtration comprising a filtration membrane (113) arranged in a housing (114) so as to separate an intake chamber (111) from an evacuation chamber (112), the inlet chamber (111) and the outlet chamber (112) each having an inlet (111a； 112a) and an outlet (111b； 112b) for fluids； - a treatment bag (140) having an inlet (140a) and an outlet (140b) fluidly connected by a recirculation line (150) to the outlet (111b) and to the inlet (111a) of the inlet chamber (111) of the filtration device (110), respectively, allowing circulation of the hemorrhagic liquid in the recirculation line (150) in a direction from the outlet (140b) of the treatment bag (140) to the inlet ( 140a) from the treatment bag (140) through the inlet chamber (111) of the filtration device (110)； - a cleaning line (180) fluidly connected to the inlet (112a) of the discharge chamber (112) of the filtration device (110) for supplying a cleaning liquid into said discharge chamber (112)； and - a first flow regulator (181) arranged for flow regulation in the cleaning line (180) and a second flow regulator (131) arranged for flow regulation in a discharge line (130) fluidly connected to the outlet (112b) of the discharge chamber (112) of the filtration device (110), so as to be able to control the pressure of cleaning liquid in the discharge chamber (112).L'invention porte sur un système de traitement, et son procédé d'utilisation associé,d'un liquide hémorragique préalablement prélevé un patient en vue d'une autotransfusion, incluant une unité de traitement (100) du liquide hémorragique, ladite unité de traitement (100) comprenant: - un dispositif de filtration (110) pour filtration tangentielle comprenant une membrane de filtration (113) ag
