The present invention relates to a colostomy appliance with a flushable insert that can be removed and replaced without removing the outer bag, allowing for quicker, easier, and more sanitary disposal of fecal waste. The appliance is comprised of a faceplate with an attachment ring that has a lip and a catch, an outer colostomy bag with top and bottom openings that can be temporarily closed, and an insert made of a flushable material. The insert has an opening that fits over the attachment ring and is aligned and secured in its proper position inside the bag by the lip and the catch of the attachment ring. The present invention also provides a method for using the flushable insert with a colostomy appliance.