Boston Terrier with possible cushing disease

Question
Hello,
I think my 9 Year old Boston Terrier, Otis, has cushing disease or PDH but am having trouble getting the vet to understand that. I have already forked out $250 on blood test which show NOTHING and now they want to do a $250 unltra sound.  I feel like he has all the symptoms of Cushing disease, lots of water, frequent unrination in the house, hair loss, skin turning brown where fur was once white, and a strange oder with skin or hair and large appetite. He does not have a pot belly but He is so thin I don't think you could tell in him anyway. He has lost weight from diarhea mostly and upset stomach so we changed food to what vet recommended and it didn't help so now I am cooking Turkey, rice, Barley diet and even added milk with baby rice to try and fatten him up.  This seems to work and he is looking better except for his fur.  My question is if the Ultra sound is neccessary??  Can't we just start that drug for to control the cortisal?  Do we have to keep running test that cost hundreds of dollars??  I love my dog dearly and he his so sweet still full of life but I just feel like I am getting the run around from the vets to get my money.  Give me something to help my little guy that is all I ask enough with the testing!  Should I tell the vet to just give me the medicine which I know you have to be careful with or should I let them do the ultrasound?

Thank you,
Amanda and Otis

Answer
IF they have run the ACTH stimulation test and/or the dexamethasone suppression test and these tests are negative, then the dog probably does not have Cushings.  Do you know if the dog's urine is dilute or concentrated?  Diabetes insipidus can also show up this way.  Ultrasound will tell them if the adrenals are enlarged, and it may also show something else inthe abdomen causing the problem.