Urine bag for collecting body fluids

A bag for collecting body fluids, such as urine or vomit, wherein the bag in compact condition includes a front side, a back side, a bottom and at least two side edges, where a bag opening is formed opposite the bottom. The bag includes an expandable bead arranged in or close to the bag opening to keep the bag open. The bead can have several chambers that can be inflated or expanded by a resiliently deformable material arranged in the chambers. A removable absorbing material is arranged at the bottom of the bag so that a sample of the fluid can be taken before it is absorbed. At least a part of the sides of the bag can be transparent. Identification means can be provided to enable identification of the user whose liquid has been collected. The bag and the bead can be compressed and stored in compact condition.