A device for providing fluid to an organ within a living body, comprising: an elongate member including a distal portion configured for insertion to a target location within a living body, the elongate member including a withdrawal lumen extending therewithin from an outlet in a proximal end of the elongate member to an inlet at a distal end of the elongate member, the inlet opening into a target organ when the distal portion of the elongate member is in the target location, the elongate member further including an infusion lumen, the infusion lumen extending from an inlet in the proximal end of the elongate member to an outlet which, when the distal portion of the elongate member is in the target location, opens into the target organ, wherein the elongate member includes a wall separating the withdrawal lumen from the infusion lumen, a first portion of the wall being configured to move between an expanded configuration and a collapsed configuration in which a cross-sectional area of the first portion of the infusion lumen adjacent to the first portion of the wall is reduced as compared to the expanded configuration so that a cross-sectional area of a first portion of the withdrawal lumen adjacent to the first portion of the wall is greater when the first portion of the wall is in the collapsed configuration than when the first portion of the wall is in the expanded configuration, wherein the first portion of the wall is configured such that it is maintained in the expanded configuration when a differential between a force directed radially outward against the first portion of the wall and a force directed radially inward thereagainst is greater than a positive threshold level. an elongate member including a distal portion configured for insertion to a target location within a living body, the elongate member including a withdrawal lumen extending therewithin from an outlet in a proximal end of the elongate member to an inlet at a distal end of the elongate member, the inlet opening into a target organ when the distal portion of the elongate member is in the target location, the elongate member further including an infusion lumen, the infusion lumen extending from an inlet in the proximal end of the elongate member to an outlet which, when the distal portion of the elongate member is in the target location, opens into the target organ, wherein the elongate member includes a wall separating the withdrawal lumen from the infusion lumen, a first portion of the wall being configured to move between an expanded configuration and a collapsed configuration in which a cross-sectional area of the first portion of the infusion lumen adjacent to the first portion of the wall is reduced as compared to the expanded configuration so that a cross-sectional area of a first portion of the withdrawal lumen adjacent to the first portion of the wall is greater when the first portion of the wall is in the collapsed configuration than when the first portion of the wall is in the expanded configuration, wherein the first portion of the wall is configured such that it is maintained in the expanded configuration when a differential between a force directed radially outward against the first portion of the wall and a force directed radially inward thereagainst is greater than a positive threshold level. <EOS>