Implantable access port including fluid handling features

A medical method, comprising:

• implanting an access port into a body, the access port comprising:
• a reservoir including a side wall with a side opening, a top opening, and a bottom surface;
• a volume control device positioned in the reservoir, the volume control device including:
• a floor having an outer perimeter configured to provide a fluid seal against the side wall of the reservoir and a top surface parallel to the bottom surface of the reservoir;
• and
• a spring element positioned between the floor and the bottom surface of the reservoir;
• a septum covering the top opening of the reservoir, wherein a volume of the reservoir is defined between a bottom of the septum and the floor;
• and
• a stem including a lumen in fluid communication with the side opening of the reservoir;
• inserting a needle through a surface of the body and through the septum into the reservoir until a tip of the needle contacts the floor;
• increasing the volume of the reservoir by moving the floor from a height-extended first position below the side opening to a reduced-height second position adjacent the bottom surface of the reservoir;
• injecting a fluid into the reservoir through the needle;
• and
• removing the needle from the reservoir, wherein resilient expansion of the spring element moves the floor from the reduced-height second position to the height-extended first position.