A urine collection bag (1) which includes an anti-reflux valve (7) is provided. The bag is made of foil layers (IA, IB) welded together so that the valve is provided by welding four foil layers together. The valve is placed at the inlet (6) and has a width so that it can cooperate with a catheter which is inserted in the inlet. The length is at least 2¼ times the width. Furthermore, a kit of parts which comprises a urine collection bag and a catheter (200) is provided.
