I did a flush before a doctor's visit and all my tests were off, eg I had no B12 and all the other readings were off too.
My suggestion is not to do the flush if you are planning to do surgery. You want them to have the right information when they give you medication or anesthesia.
If you want to do the flush cancel the surgery and keep going and read on the forums here what to do next.
A lot of us needed surgery and are holding off.