You should NEVER give an inappetent dog Metacam! (Or any other NSAID). You are asking for not only GI ulceration, but major bleeding and potential perforation.
Metacam is a wonderful product, for most dogs I like it hands down over previcox, dermaxx, rimadyl etc. However, with already increased liver enzymes and inappetence I dont thnk many vets would prescribe it. Tramadol is safer on the GI, and is often given as palliative treatment for pain control.
As far as an xray, please reconsider if you can. I routinley do radiographs on stressed sick animals. I use sedation (NOT anesthetic) based on the animals temperment/illness. A mild narcotic would be ideal for your dog, something like hydromorphone or buprenorphine that give the patient PAIN CONTROL as well as a sense of euphoria. They are not “out” but rather, quiet happy. They can still walk, eat, drink etc but are relaxed. Any good practice does not twist or roughhouse a dog for radiographs (which is why I am a huge fan of mild sedation/anagesia). Radiographs may/may not rule anything out, but an abdominal view can give you a rough assessment of the hips at the same time. What would likely be evident on xray would be something like a large liver or splenic mass, and if this is the case its peace of mind that you can make an educated decision regarding euthanasia or not. If it truly is the hips, and the abdomen is fine then there are ample other pain management techniques available if you should choose to proceed. My biggest concern would be the lack of appetite…usually pain from arthritis doesnt cause a dog to stop eating.
Please keep us posted as we are all jingling for your old guy 
