Arrangement to introduce a liquid medium, for example urea, into exhausts from a combustion engine, which arrangement comprises: - a mixing chamber intended to be perfused by exhausts, wherein the mixing chamber is delimited in a radial direction outwards by a first tubular metal wall and which mixing chamber has an upstream end and a downstream end, and - an injection element for injection of the liquid medium as a spray into the mixing chamber, characterised by - the arrangement comprising an exhaust channel arranged downstream of the mixing chamber and adjacent to the mixing chamber, intended to be perfused by exhausts and extending along the outside of the first tubular wall, so that the exhaust channel is delimited from the mixing chamber by the first tubular wall, and connected to the mixing chamber via a flow reversal element, which is arranged to reverse the flow direction of the exhausts flowing from the mixing chamber, so that these are brought to flow through the exhaust channel in a flow direction which is opposite that of the exhaust flow direction in the mixing chamber. - the exhaust channel being delimited in a radial direction outwards by a second tubular wall, which is designed to guide the exhausts flowing through the exhaust channel so that they pass on the outside of the wall section of the first tubular wall, which is intended to be impacted by said spray of a liquid medium from the injection element, and - a throttle being arranged in the section of the exhaust channel, which is located closest to the upstream end of the mixing chamber, on the outside of said wall section, in order to achieve an acceleration of the exhausts flowing through the exhaust channel in the exhaust channel section, so that these flow with an increased speed over the outside of said wall section. - a mixing chamber intended to be perfused by exhausts, wherein the mixing chamber is delimited in a radial direction outwards by a first tubular metal wall and which mixing chamber has an upstream end and a downstream end, and - an injection element for injection of the liquid medium as a spray into the mixing chamber, - the arrangement comprising an exhaust channel arranged downstream of the mixing chamber and adjacent to the mixing chamber, intended to be perfused by exhausts and extending along the outside of the first tubular wall, so that the exhaust channel is delimited from the mixing chamber by the first tubular wall, and connected to the mixing chamber via a flow reversal element, which is arranged to reverse the flow direction of the exhausts flowing from the mixing chamber, so that these are brought to flow through the exhaust channel in a flow direction which is opposite that of the exhaust flow direction in the mixing chamber. - the exhaust channel being delimited in a radial direction outwards by a second tubular wall, which is designed to guide the exhausts flowing through the exhaust channel so that they pass on the outside of the wall section of the first tubular wall, which is intended to be impacted by said spray of a liquid medium from the injection element, and - a throttle being arranged in the section of the exhaust channel, which is located closest to the upstream end of the mixing chamber, on the outside of said wall section, in order to achieve an acceleration of the exhausts flowing through the exhaust channel in the exhaust channel section, so that these flow with an increased speed over the outside of said wall section.