| You do need to take her to a vet to be sure, but it kind of sounds like an infected and probably burst anal gland. Dogs have glands on each side of their anus that has this nasty liquid in it that is supposed to be squeezed out a little at a time when they defecate. Sometimes this doesn't happen and the gland can get impacted, infected, and abscessed and eventually it will explode outward. Disgusting huh?
If this is it, she will need it cleaned up and to be put on antibiotics. Please call your vet for an appointment as soon as possible. | 
