I would argue about the diet related thing. The only dog I have ever had where it was a problem did have bones, his poo was solid (sorry tmi!!) and he still had constant problems. The vet taught me to evacuate them myself as he said that if a dog was going to have probs, regular emptying was the best chance of managing it. He was right, once I started regular emptys, he stopped getting the infections. His companion needed hers doing about once a year or less, again, same diet. My last weimaraner never had a problem the whole of her long life, fed on quality dry food no bones given, and my current two seem fine so far, again quality dry food no bones. Please please get this poor dog's rear end sorted then take advice on future prevention, diet won't cure an infection or prevent an abcess.