First, the most important news: Marlin is FINE.

The lump: is either a benign tumor, or a reactive fibroplasia. Either way, I just have to watch it in case it decides to grow rapidly, otherwise we can ignore it. A reactive fibroplasia may be caused by a vaccine, or by a wound healing. As he hasn't had any vaccines since August, maybe he got a wound that is healing.

Blood work is perfect. Vet suggested 3 possibilities:
1. We've been trying to keep Marlin at 16 pounds, slightly underweight, to help his hips last as long as possible. Being a chow hound, maybe we just can't do that with Marlin and will have to let him be at 17 to 18 pounds.
2. I've been feeding grain free for 2 years this month. Perhaps that, along with keeping his weight low, it too much, and I need to add some oatmeal or rice to help him feel full longer.
3. He likes the food, and has learned that whining and fussing gets me to give him MORE. In other words, he is playing me!

The urine sample is borderline for a UTI, so he is now on antibacterial meds for 10 days for that.

So about $400 to learn my chow hound is playing me!

I am quite relieved, but also a bit mystified with all he's been doing. So I'm going to feed him more, get through the meds, and see if things calm down around here.