Acute renal failure can come on so suddenly and we never expect it to end the way it does. My cat Peeka passed from it but she was 14 when it happened. So it's understandable that you're puzzled about it b/c Kiba was so young. Please know that Kiba is now at peace and she knows how much you loved her and still do. I hope that you're able to find peace soon, too. RIP, sweet Kiba.