prolonged use of Prednisone for tx of skin allergies

Question
I have a Westie who just turned 15 yrs. old.  He has been treated for skin allergies for years.  We go to Florida in the winter and he is miserable down there.  Two yrs. ago he was treated with Revolution to R/O Scarcoptic mites.  He probably had only two tx and then I switched him back to Frontline so he would be protected from ticks.  I don't think that he ever got rid of the mites.  I took him to Vet 3 wks ago because he had a bloody stool.  I asked him why Bailey was so itchy this time of year--How could it be allergies?  He looked back in records and suggested it might be mites.  He gave him an oral dose of Ivermectin .2ml (1%).  Since then, Bailey has lost appetite, vomited several times.  I took him back to see Vet and he gave him Cerenia and did blood work.  On physical exam, he felt no liver enlargement or tumor.  His liver function is very elevated.  He recommended an ultrasound which will cost $310.00.  Do you think Predisone and Benadryl (3 x day) and Ivermectin has cause elevated liver function?  The Cerenia can elevate liver function--so I don't know why he gave it to him.  I only gave one dose.  I know there is a great possibility that my dog has liver cancer.  Can he be treated with some medication to normalize his liver function first without doing ultrasound?

Answer
Dogs livers are very sensitive to steroids.  It causes a benign liver enlargement called steroid hepatopathy.  The liver will enlarge and the enzymes will elevate (Especially the Alkaline phosphatase and the ALT).  The liver enlargement will cause a large belly and somtimes panting.   If the dog has sarcoptic mites, an insectidical dipping in either amitraz or phosmet will kill the mites.  Westies are known for their allergic skin disease.  An alternative to Prednisone is Atopica (cyclosporine).  Also treat the skin or any secondary bacterial or yeast infection, as they both contribute to the itchiness.

As far as the ultrasound,  if the dog is off steroids for several months, the liver enzymes should decrease. If they do, then the ultrasound may not be necessary.  If the liver enzymes remain elevated then an ultrasound is probably indicated to see if liver disease is the reason for the elevation.