Infection in my Asian common toad?

[WilliamCWitherstone]

Hi, I’m new to this forum and I’m sorry to have to start my first post this way. I have been keeping an Asian Common Toad since the 24th of November last year. He was found on a concrete walkway by the road one rainy night. He has been a big eater since then. He was consuming 3~5 crickets every two days for the first 2 weeks before we switched to mealworm, which he takes in around 7-10 every week up until 2 weeks back. Usually, he reacts instantly when he sees food. He stopped eating for a few days before his last meal of a single mealworm 2 weeks ago. He has been avoiding food since then -- if I hold a worm in front of him for a while, he’ll turn his head somewhere else.
We thought it’s getting cold so we upgraded his shelter and placed a light 50W spot light. The light is kept on 8hr a day, giving ~ 86°F right under the light but ~ 75°F for other regions. Didn’t bring his appetite back though. Around the same time, we also observed that he stays in water way longer than he used to -- a few hours a day to the whole night recently. This might have been caused by the heat and lowered humidity. I kept the light off yesterday but he still spent the whole of his last night in the water.
We brought him to a vet on the 12th of Jan, where they took 2 x-ray images and performed some inspections. It was shown that there is a mass in his belly. The vet is unable to tell what that is without further tests. The vet also noticed that his gorin is a bit red but we were unable to tell whether it was like that from the beginning or it is something new. We returned from the vet to wait for a week for observation and see if anything changes. Here are the X-ray images:





As of today, 15th Jan, we noticed a darkened region on his belly which was not there before. His gorin also seems to be a bit redder than it was. We are thus making this post asking for second opinion before we visit the vet again in the next 24 hours.




Other notes:

• SVL 6.5cm
• He is still active and does not show any sign of weakening
• Tried switching back to crickets, didn’t help
• Tried dubia, didn’t work
• Vet tried to open his mouth for inspection but he refused to comply
• His last excrement was found on the 10th. Dried though, could tell when it was from. That was half the size of his usual stuff but of the same color -- dark grey.
• Bathing water is changed daily, dechlorinated, boiled and cooled to room temperature
• We reside in Hong Kong where the temperature was around 75°F in December before he started to refuse food. It gets cooler in January but the temperature normally will not be lower than 60°F.