Thanks for your thoughts, Kathryn. I agree that more testing needs to be done. But, in the moment, does anyone know how quickly metronidazole works? I think it is supposed to be very fast-acting and I don't want to force it on him if it is not helping, especially since I think it hurts his stomach. (My sister had to take it once and it hurt her stomach.) He's so miserable it's just breaking my heart.
(FYI, Kathryn, the dogs prostate gland can be palpated via the rectum and the vet agreed that it might be triggering his urge to go.) But why would it be enlarged? He also said that it felt "healthy" for what that's worth.
Again, my thanks.