looks like a small prolapse of the end of the intestines near the vent. the fat stored around the tail base doesn't help but the skeletal kinks are prolly the main cause. really don't know what you can do about this. try to shrink it a bit with a soak in saline water but it'll prolly recur with the next defecation. the vet can also prolly reduce the prolapse and suture it to the vent so it doesn't happen again. i some times wish breeders would stop selling kinked babies at "discounted" prices so heart breaking issues like this does not occur.