Abstract: The prosthesis is configured like an anti-return valve ranged preferably in the area where the esophagus and the hiatal hernia meet. Said valve is comprised of a tubular part associated with an annular fixing element. The tubular part flattens progressively to form two joined lips. It is possible to form said valve with a wall thickness which increases from the free end of the lips towards the annular fixing part in order to avoid an easy returning under the effect of the surging pressure. During the passage of the alimentary bolus, the lips are spaced apart and joined again owing to their natural elasticity. A metal wire embedded in the annular fixing part is used for the radiologic marking.