Thanks Carlos! I wasn't able to palp the swollen area as the frog was very stressed, I've taken him out the water soak now and noticed that he has pooped but I'm not sure the poop looks normal. Instead of being the usual brown colour it was a bit brown but the rest lighter and cloudy. I can provide a picture if necessary! Is that a sign of anything? I have to say the frog looks like his belly is more squishy when he's moving around rather than hard. I can't quarantine him right now as I have to thoroughly clean another enclosure for him, but I will do soon.