A collapsible liner for use in a canister of a medical fluid collection system isdisclosed. The liner includes a flexible bag extending longitudinally between atop portion opposite a closed bottom portion, and at least one support element connectedto the bag and disposed generally laterally relative to a length of the bag. Whenan interior of the bag is subjected to a vacuum, the at least one support elementlimits an extent of lateral collapse while permitting longitudinal collapse.