A delivery device may be configured to deliver an agent to a target tissue through a channel of a medical device, the delivery device may include a body including (a) a coupling region configured to removably attach to a handle of the medical device, and (b) a coupler including an exit port for aligning with a port of the channel, wherein the coupler is configured to mate with the port of the channel; a source of an agent; and a source of pressurized fluid. The body, the source of agent, and the source of pressurized fluid may be arranged to deliver agent and pressurized fluid to the exit port for delivery through the channel.