This morning, I noticed a tiny wet spot on Buster's his shirt (he's been wearing shirts per the vet's suggestion)...it was about the size of a pencil eraser or maybe smaller. I peeked under his shirt and saw a little wet place next to his incision. I called the vet and she said it sounded fine, that some drainage is normal and to keep an eye on it and let her know if it changed.
I got home after work and when I walked in the door, he got up out of his bed to go potty (they use pee pads) and I noticed that half of his shirt was wet. So I freaked out and picked him up to see what was going on. I was having a hard time lifting his shirt up because it was wet and I was worried about the staples (the incision is LONG) but what I could see did not look good....so I just wrapped him up and we jumped in the car and headed to the emergency vet (regular vet's office was closed). I got to the vet and they took him back, cut the shirt off to examine him and finally I got to go back and talk to the vet. Bottom line is that he has a bad infection - apparently it's common for infections to appear suddenly like this (it had been there for a few days "brewing" but just suddenly became visible). She said in these cases, the infection grows underneath and then comes through very quickly where it finds a weak place (in his case, beside his incision where the staples were going into his skin). Of course I had no idea the names of all the meds he's on so I had to go home, get them, and go back. He's there right now and I should be able to get him about 11:00 tonight. They're going to sedate him, open the area, clean it as best they can, and remove the tissue that's bad/dead/dying. They can't really close the area because of the infection and they need to be sure the infection is gone before they close it back up so I'll have to take him in daily to have it assessed and re-bandaged. Hopefully after a few days, they'll be able to close it. The other concern is that there's not a lot of skin there and what is there is already pulled tight so if they have to cut away much because of the infection, that may lead to other problems.
Poor little guy! He's been through so much. He seemed to be feeling ok though which made me feel a little better. He was very alert and sat up in the car (propping himself up with his one front leg).