The invention relates to a coupling device (2) which includes a coupling member (3) including a primary flow channel ( 11) and secondary flow channels (12) each provided with a proximal opening (13) intended for being in fluid communication with a respective tube for delivering mdical treatment fluid and a distal opening (14), the distal opening (14) of the primary flow channel ( 11) being arranged between the distal openings (14) of the secondary flow channels (12), and a connection nozzle (4) to be connected to a cathter, the connection nozzle (4) including a mounting portion (15) in which the coupling member (3) is mounted, the coupling member (3) and the connection nozzle (4) defining an inner chamber (18) into which the distal openings (14) of the primary and secondary flow channels ( 11, 12) lead. The cross section of the distal opening (14) of the primary flow channel ( 11) is larger than the cross section of the proximal opening (13) of the primary flow channel ( 11).
