Hi Ratmom,
I love rats also and we have 2 of the cutest white ones at our shelter right now. Really intelligent pets.
Before you take Oliver to your vet make sure that your vet is very rabbit knowledgeable. If you don't know I can give you a list of Mi. vets . The reason I'm stressing this is that it does sound like Oliver has a couple of abscesses and different vets will treat in different ways.
Some vets will want to open them and drain them or pack them with antibiotic beads >We have had a number of members of this forum whose rabbits have had jaw abscesses. These things are difficult to treat and nothing like rat problems. The reason they are so difficult is that the rabbit's body will try to "wall off" the infection creating a tough abscess wall which is difficult for many antibiotics to penetrate. Even opening them and expecting them to drain is not productive as they won't drain...rabbit pus is like tooth[paste. They are sometimes opened and scraped to remove the pus and left open and flushed
Jaw abscesses are particularly difficult to treat particularly if they are attached to the bone or teeth are involved. You need a very saavy vet to treat this.
Many of the forum memebers have had success with the use of 2 antibiotics rather than 1.
The drug called bicillin is a combination of a short and long acting penicillin. it is administered subqutaneously (under the skin) to the rabbit every other day for a lenghty period of time. In addition to this another oral drug is often given topack a synergistic punch to the infection and knock it out ( paraphrasing ra7751). A culture can be taken of the pus for culture but oftentimes many vets will prescribe baytril or ciprofloxicillin or some other 'safe" rabbit drugs when a stronger drug like zithromax or chloramphenicalis much more effective. Many vets have not been trained to give rabbits anything more than 1 or 2 basic drugs and often these drugs are not strong enough.
Your vet should take head -xrays and dental xrays to see if the teeth are involved. hopefully the teeth aren't involved as that complicates the process. You can see why you need someone who knows his stuff (which should be rabbit medicine )
One of our memebers (who owns a rabbit rescue and is a wild-life rehabber) believes that surgery is oftentimes not a necessity if the abscesss is treated aggressively with drugs.
I don't think this necessarily applies if abscessed teeth are involved.
Anyway I will give you some articles to read.
Do your homework before you go to the vet so you can ask questions..but do it fast as these things seem to spread and grow like wildffire.
You came to the right forum for this issues as we have dealt with a lot of abscess problems.
http://www.rabbitsonline.net/view_topic.php?id=11791&forum_id=10
http://www.rabbitsonline.net/view_topic.php?id=11576&forum_id=9