A catheter (10) for delivering an agent to an injection site in a wall of a patient's body lumen, with an elongated shaft (11) having a needle-through lumen (12) slidably containing a needle (13) therein, and an expandable member (15) on the distal shaft section which has a collapsed configuration and a radially expanded configuration. In the radially expanded configuration, the expandable member supports the shaft in a position spaced away from the body lumen wall, and the needle slidably exits the needle-through lumen in the extended configuration through the port (14) spaced away from the body lumen wall as a portion of the expandable member maintains the position of the port section of the shaft in the body lumen. The expandable member typically has an open-walled, helical, or lobed configuration providing a perfusion path along the expandable member.