Without a gallbladder makes it difficult to get as many stones out, but it is still very helpful because your bile is not pumping well without a gallbladder.
I have heard of others using coconut oil instead of olive, but I have not tried it.
It is the oil that causes the bile to start pushing the stones out and the epsom salts relaxes the bile ducts and billiary ducts so that the stones do not get stuck.
I prefer the Dr Clark Liver Flush, but many have other recipes.