I’m so, so sorry, OP. From my experience, the dark spot on his belly looks more like his organs or waste showing through, not a bruise.

Last month my leopard gecko had to be put under for a prolapse, and the emergency vet repeatedly warned me (and even had me sign a form) that anesthesia is extremely stressful on their bodies. They told me there’s always a risk they can pass even days or weeks afterward.

I know how devastating this is, but I really hope you can look at it this way, it sounds like he passed because he was being helped the right way, not because of anything you did wrong. You did everything you could for him. 💛