Hi there,
I am sorry your kitty has been through so much lately. What you are describing sounds like an injection site reaction, and it may be from the Baytril he received. Baytril can cause an abscess like reaction if not given completely sub-cutaneously (under the skin). This does not mean that your vet is negligent, or that the drug was administered incorrectly, this is something that can sometimes occur. If the baytril was given intravenously when your kitty was on fluids, then this reaction is due to the anti-inflammatory that was given. The newer anti-inflammatory of choice now is called Metacam, and it is also possible that this drug (or a variety of others) could cause a similar injection site reaction. We have a clinic cat who developed a similar reaction several weeks ago, and he is healing nicely.
You can expect that this site will continue to leak, and if it continues to be clear fluid that is good. It may abscess and the discharge will change to white or pink tinged in color. the skin over the area may necrose and die, and fall off or form a scab which eventually falls off. As long as there is active drainage, that is a good sign. If the area seals itself over and becomes swollen, red or painful and your kitty starts to feel badly and stops eating, then it is time to go back to the vet.
Please let me know if I can be of further assistance. If this has been helpful, please hit the green accept button. I hope your kitty continues to feel better, and that his recovery is quick and complete. Keep a close eye on his urination, and be sure that he is still going on his own and doesn't reblock. Good luck!
Emergency Critical Care Nurse
16+ years of veterinary experience