I'm with Fergi. Usually a warm rag will uncakethe poop. I also after finding a bun like that the first time...willcut some of the fur away from that area so that poop doesnt get stuckas easily the next time.
Is the poop stuck in the fur, or is it stuck in the rectum? Either waywarm water and some *gentle* persuasion with a warm rag should help.
Lanna