The way I understood it, keto (inc. carnivore) actually clears the accumulated uric acid crystals from where they settled in the body (joints, kidneys...), in effect doing the same job as Alopurinol. This can temporarily elevate uric acid in the blood, and cause gout-type pain.
It happened to me a few times when I started the carnivore diet, but every successive bout was milder, and I haven't had any issues for over a year now. I was prescribed colchicine for the pain. The doctor also suggested Alopurinol, but I didn't see the need.