It has to be Epsom Salts because that's magnesium. Being low in magnesium means your muscles and bladders cannot relax, which gives them less room to retain fluids. If you constantly have to urinate and only small amoutns come out, first thing to check for is magnesium deficiency.
The plain flushing enema is Sea Salt and water, that's it. You can do othre things but this is the easiest. To cleanse the liver do a coffee enema, but they are intense so only once a week or less.
I like Colonix because that way you get cleansing/laxative tea and fiber as an all-in-one program. But if you already have the fiber you can get Clarkia and probably save money? Since you don't tend towards constipation anyway. Both products have many success stories and their manufacturers are good people.