The Hebrews considered the bowels and internal organs the seat of the emotions, in the same way we speak of our hearts today. Isaiah is therefore expressing his grief intensely. As Isaiah declares only what God commands, we know that God is also moved by Moab’s plight.
However, the reason for this even more intense grief is not the destruction of Moab, but their reaction to it, as seen in the next verse.
11 Aussi mes entrailles frémissent-elles sur Moab, comme une harpe, Et mon cœur sur Kir-Harès.