The present invention relates to an implantable medical device comprising a device body having an internal reservoir configured to expand in size. The device can comprise an anchor structure affixed to a wall of the device body and having an interior passage, a conduit having a fill end and a device end with a conduit lumen extending therethrough, and a plug-port member comprising a shaft section opposite to a plug section, with a port section located therebetween. The device end of the conduit can be coupled to the shaft section and the plug-port member can be located within the interior passage such that in a fill configuration, the port section and the plug section are located within the internal reservoir allowing the fluid to pass from the conduit lumen into a shaft lumen, through one or more port openings in the port section and into the internal reservoir.