It's quite likely nobody is going to be able to tell you what the consultant is looking for. He may not even be looking for any specific thing. I guess it's possible he is trying to find out more about the degenerative disc? 

Did you ask him what he was investigating? Was there a context? I mean, are you consulting him about the degenerative disc or was there something else, like he found a swollen lymph node? If it's the latter, it could be to confirm that it is lupus that is causing the swelling and not something else,

I'm no expert so these are oinly guesses. Your consultant is probably the best person to tell you if he is concerned about anything in particular or if this is just a routine thing.