I would get a very close look Stacie, to make sure of what it is your seeing. There are a few things it could be.
First of all, what color is it?
Are you sure it is not their innards, having possibly used their stinger in defense? I have often seen workers make it back to the hive after their sacrifice.
Could it be a parasite infestation? I have had weak colonies invaded by earwigs, and witnessed bees being removed from the hive still alive, but with an earwig embedded in their abdomen. And most recently, having the joyous occasion of welcoming my favorite parasite of all back to my yard, SHB have infested a week nuc, and some of those brood have been eaten while still capped in their cell. But worse yet, I have seen some of those workers emerge with partially consumed abdomens.
If their is a glob of brownish/orange goop coming out their business end, It could possibly be nosema. Do you notice streaks or spots of the same color inside the hive, on the frames, or on the outside of the hives?
On a parting thought... Do one last check. Smell it, does it smell like poop? Taste it, does it taste like poop? If the answer is yes, be glad you didn't step in it...