My 13 year old dachshund has been having problems with diarrhea (with mucus and sometimes blood) on and off since mid-October. She is acting completely normal--eating and drinking fine and doesn't show any signs of weight loss. The only time that she acts like she doesn't feel well is when she is actually having diarrhea outside. After she gets back inside, she acts like nothing ever happened and wants to eat again. Her doctor has had her on bland diets, Metronidazole, and now she has recently been put on a de-worming medicine (fenbendazole). She has had blood tests, x-rays, ultrasound, and fecal exam and culture, and everything came back fine. She was put on the de-worming medicine to see if it could work, before having to do anything invasive like a colonoscopy. Within a few days of being on the de-wormer, her stool began to look perfect. But then about a week after being off of the de-wormer, she began to slowly have her diarrhea come back again. So her vet wants to put her back on three days of the de-wormer now instead of waiting until three weeks pass (like he was originally going to have us do). Since the de-wormer helped so quickly does that mean that it is likely that she has worms? Or is it possible for a de-worming medicine to help diarrhea go away even if they do not have worms? She has had one dose of the second round of the de-wormer, and so far, her diarrhea seems to be the same. I am really hoping that the medicine will eventually start to help, and make it go away completely this time, since the next step would be a colonsocopy. I am so scared to have her go through that. For the past four years, she has been on medicine (an immune suppressant along with a low dossage of steroids) for her immune mediated arthritis. She is also on soloxine for her thyroid problem. Does any one know what else this sounds like if it is not worms? Thank you so much for any help!