An open top enema is one that has an opening at the top and the tube connects at the bottom. This allows you to refill the enema easily, even while it is in use. These types of enemas are popular with people who use enemas for cleansing. Using an open top enema allows you to take more than one enema repetitively. One downside to open top enemas is they are easier to spill, so you will want to hang yours carefully.