Cat has severe inflammed mouth gingiva with bloody ulcers. Cortisone/antibiotics help temporarily. Any help

[Marcellus Wallace]

My vet has treated him with fluids, time release antibiotics and methypredinisolne injections (20 mg) and .35 (Covenia). This seems to help for 1-2 months. But, it always returns. He is eating Royal Canine Rescue canned food and loves it. Can't eat dry food. Help!!

[Foghorn Leghorn]

When my cat had a similar issue, it was because kidney failure had started. Has your vet checked his kidneys?