A continent ostomy port device has a face plate defining a selectively sealable aperture which is alignable with the opening of a stoma formed in the body of a user of the device. A closure portion is adapted to permit selective and repeatable covering and uncovering of the aperture in the face plate. A catheter portion extends from one side of the face plate and extends proximally, and one end of the catheter portion is disposed interior of the user's body, within the ostomy site, when the port device is in normal use position. The catheter portion has continuous exterior and interior side walls, the latter defining a major lumen. The catheter portion is sized and shaped appropriately for non-surgical installation through a stoma to a sufficient distance that the presence of the catheter portion within the stoma provides a physical barrier which reduces the incidence of stoma prolapse, without the use of extraneous, externally applied materials or additional surgery. Retaining structure is connected to the catheter of the continent ostomy port and is non-surgically, snugly fittable into the stoma, to cause the port device to be self-retaining in a normal use position within a stoma of the user, without the need for special surgery or extraneous, external fixation materials such as tape, belts, and adhesives. The retaining structure is also usefully connected to other medical catheters.