Hello,
I hope that your cat is doing better.
Many cats have discomfort when urinating for the first few days after the urinary catheter is removed. This is normal. Make sure he is able to urinate (pass urine) I usually recommend a prescription urinary diet and ask about any and all options to help manage inflammation (I like a few things so ask your vet which might work for you (nsaid, steroid, other anti inflammatories) pain medication (analgesics) and any way to increase fluids ( there are lots of options like sq fluids at home, adding water to food or hydra care).
As far as defecating goes. I only worry if they are straining to defecate and unable to. In almost all cases they are not eating well in the hospital to form a stool. So it can be days before they poop normally.
Hello
Seromas can take quite a long time to resolve. I have seen it take weeks. Or even 2-3 months. The key is that it is never bothering your dog and never shows any signs of being n infection.
In my experience it just has to reabsorb on its own and on its own time.