it could be that the bladder is inflamed and causing the tummy to swell..or a stone thats causing the irritation will cause very frequent urination..he needs to have a pelvic MRI with contrast to see whats going on for a propper diagnosess..and that theres no interior bleeding from the stone..watch colors of stools ifd there black or throwing up a substance like coffy grounds get to ther er asap..a stone this big can cause major infection or bleeding..and if on narcotics for pain can also cause more irritation..
I'm going to have to disagree here and say get to the ER asap. Hard tissue and that much swelling with a kidney stone over 4mm usually means a blockage. With diabetes that could be deadly. I hope you get him in soon. Good Luck.
I left something out. Even with one kidney blocked you can still pee, because the other kidney is still functioning.