A collapsible liner for use in a canister of a medical fluid collection system is disclosed. The liner includes a flexible bag extending longitudinally between a top portion opposite a closed bottom portion, and at least one support element connected to the bag and disposed generally laterally relative to a length of the bag. When an interior of the bag is subjected to a vacuum, the at least one support element limits an extent of lateral collapse while permitting longitudinal collapse. The canister includes a second vacuum source port located remotely from the lid so as to subject a space between the collapsible liner and the canister to a second vacuum commensurate to the vacuum applied to the interior of the bag.
