Gus' urine culture tested negative.
Over the last couple of days, Gus' symptoms (frequent urination & thirst) appear to be less frequent, but he's not what I'd consider normal.
When the vet gave me the results of the culture, yesterday, she said she'd run a check on Gus' SG. Got the results from this morning's sample - 1.026. This is the highest SG of a samples tested.
I new it was going to be okay, before getting the results, because this was the first sample that was yellow, i.e., not clear. Conincides with the symptoms subsiding.
I don't know why the change for the better.
I have been making a serious effort to stop Gus from eating things off the ground in my back yard and on the street. Can't believe that this is the answer. Time will tell.