Did your father have a whipple? I'm asking because I found myself in a similar situation as you. My father had a whipple and now his stomach looks as though he's 9 months pregnant, even though the rest of him is very thin. I was convinced at first that he had fluid in his abdomen (acites) and questioned Dad's doctor when he told us there was no fluid. As it turned out, my father developed the largest hernia along his surgical incision that any of his physicans had ever seen. Given my Dad's medical history, it was decided that the risk of surgically correcting it was too great, so nothing is being done.
So it is possible that a distended stomach can be cuased by something other than fluid.