If I recall correctly from Chayei Adam and elsewhere, if you're in the middle of a bread-based meal and excuse yourself to defecate, first of all you should wash with soap and water for hygienic purposes, as you always should after using the restroom! But after that, you do a ritual washing and make "al netilas yadayim" as you usually would when starting to eat bread.
According to those who do require washing, however, what are the parameters of this washing? Can I talk afterwards? Do I say a new hamotzee if I'm having more bread? What if I wasn't in the mood for more bread, just cake? Just meat? Just water?