It is possible that if it's a lumbar implant and the stimulation is up pretty strong in the lower back area that it can also affect the abdomen. It's called the "band affect" and some can tolerate it, others don't. I feel it to some degree in my abdomen all the time, but it's not uncomfortable enough that I complain to my dr. as I so love the pain relief I'm getting from the implant for my lower back that I don't want to lose the pain relief so just put up with the funny feeling in my abdomen.

Another thought...maybe if it is a lumbar implant, it could be affecting an abdominal nerve improperly somehow??