[sweetlee]

the dog may be sitting right on the butt because well, after having nasty bile type diarrhea his butt may itch really bad.
I guess I would find out exactly what all they checked for. If all medical is completely ruled out, I would start over, withholding food for 24 hours but make sure the dog has plenty of fresh water. Then start back in with the bland diet. I use rice with no chicken the first day, in VERY small amounts but more frequently, just boil the rice in chicken broth to flavor it. What works even better for my boy is oatmeal instead of the rice, it adds bulk to the intestines and will help to suck up some of the bile. I also cook this using chicken broth instead of water.
My vet said it's OK to give immodium AD, use an adult dosage. But please ask your vet before you do this, in case your dog is still on any meds that may react badly with it.
If you baby's butt is itchy, you can wipe it with some Tuck's pads for people. It should relieve the the itching and burning some. Poor dog.
Sometimes the gut just needs a good rest to get out of the cycle of pooping and producing too much bile.
You may have to start over at square one, with the bland diet, start slow and easy when reintroducing food, add some chicken on day two, and at the end of day 3 you can start adding in kibble to the rice mixture,slowly.
Let us know how things are going and what the vet says about what they have tested for.

Sharon