In A Nutshell... About A Year Ago My Chihwawa Was

In a nutshell... About a year ago my chihwawa was dx with nerve and vertebra issues, was in pain and put on Prednisone, etc. It helped and we did this on and off for about nine months. Then he started with vomiting and diarrhea up ten times a day. All kinds of blood work, meds tried. It helped somewhat. Diarrhea is gone recently but still has occassional vomiting. Has been checked for atypical Addisons,Cushings, diabetes ( his sugar is a tiny bit low), but with loss of appetite for so long I expected it. Was feeding him home cooked food of rice, sweet potatoes, chicken, turkey, lean ground beef and occasionally some pork. Abd xray three weeks ago showed distended bowel with large amt of gas and little white dots scattered. Md thinks it's kitty litter. He is not a kitty litter dog. Has never had any interest in it and I never find him near it. He lost 3lbs in 2 weeks and continues to have poor appetite. Had a laporoscopy done last Thursday and found a torsion of his colon (not the small intestine aas is most common). And an adhesion. It's repaired and the post op is going good(no signs of infection and incision is healing well). But it's taken a toll since he was so debilitated to begin with. He looks like a skeleton. All bones and sagging flesh. Any ideas? What could the white specs on xray be if not litter. There is no dry wall etc for him to get at. He does not pick up anythingn off the street. He's fadding before my eyes and is obviously very sick. Two vets cannot find a diagnosis but I can see he's running out of time. He is 6yrs old. Please help me.