Well....here we go again. Don't over react to something like this. Stress can cause this. By the time you get a time to see a vet, it will most likely have resolved on it's own. If not, then it would be a good idea to see a rabbit savvy vet. Unfortunately, most vets rely on old information in treating this condition and respond incorrectly. Whatever you want to call it....mucoid enteritis, bacterial enteritis, cecal dysbiosis or any number of names....the green/yellow mucus is indeed the body's response to an irritant in the GI tract. Most of the time the culprit is Clostridium but we have seen E Coli in there too....but Clostridium is by far the most common. This is one of those times you need to "steady the ship".....don't go overboard reacting.
Clostridium is one of those opportunistic bacteria. It is controlled by the beneficial bacteria. In a GI event....stress, food problems, infections, etc., the pH crashes and the benefical bacteria starts to die off. As it dies, it decays and that is toxic. And since the beneficial bacteria keeps the bad stuff under control, as the beneficial bacteria dies, it allows the bad stuff to grow. Clostridium is an obligate anaerobic bacteria....that means it lives in an environment devoid of oxygen and will die when they come in contact with oxygen. For many years, antibiotics such as Baytril, Cipro or Sulfa drugs were used....we now know those drugs are ineffective against Clostridium and are actually harmful when they are put into a compromised GI. We have used Metronidazole for many years....it's an antibiotic that is effective against anaerobic bacteria....but it is used much more for the anti-inflammatory qualities than for antibacterial action. Questran has also been used. This is a human drug and is quite hard to find. It also have to be compounded. The up side of this drug is that it binds toxins (like Toxiban or charcoal)....the down side is that you really have to push a lot of water for it to be effective. I have most recently been using an equine product called BioSponge. It has proven to be highly effective at binding and filtering enterotoxins from specific strains of Clostridium.....and in one of those rare "wins" when it comes to rabbits, the strains of Clostridium that it is effective against is the ones we find in rabbits.
I would suggest just feeding a basic (proper) rabbit diet and stick to high quality hay and plenty of water for the next few days. A probiotic such as Probios or Bene Bac won't hurt. These products help to acidify and stabilize the pH in the gut.
Randy