D&D nothing, unless he killed and ate that dragon troll and mutated into a dragon-troll-dwarf that didn't have to eat or drink for years, he would have died of thirst and/or starvation a LONG time ago.
... and with THAT, we may have a plot point.
If you are trapped due to a battle, but don't die for days or (dwarves being very very tough) weeks later, is that "dying in battle" enough to go to Valhalla?