I had a fluid buildup only a day or two after my surgery, and while not as long away as your dad, I've yet to have another. Of course, they said I just had an obstruction or some blockage. But having known the pain myself, send your dad my condolences.
And I think everyone understands the context here to mean it was drained from the belly.
the fluid build up is actually under his skin and outside of his organs, when I said the drained the fluid from his stomach I ment to say they drained it from his belly. Thanks.