There are alot of things that can trigger the thought of renal disease....One of the signs can be the concentration of the urine. With kidney (renal) disease.... the urine is not concentrated at a normal level and becomes water the body then will tend to lose too much water.
One test they will run is a specific gravity test on his sample (and it is better to have a fresh sample for this) Normal is usually above 1.025....Pets that may be having an issue of kidney disease will read around 1.008 - 1.012 range. This test has to be repeated to make sure there is more then one low finding and not a sample that has been diluted with water drinking.
All of that said....there are other things that can cause an issue of this sort and renal disease can sometimes be found in young dogs as a birth defect, but it is generally found in older ones...so dont get upset until you know what you are dealing with.....
The general signs of kidney issues are:
Increased water consumption, less urination or lack of going, going at unusual times or places, blood in urine, wont eat, vomiting, lethargy
diarrhea, reluctance to move or tender when you touch the stomach area, Dull and dry hair coat and skin, color of the inside of mouth and inside of ears and mouth sometimes has a yellow to orange tint in color.....
Sorry you are having such a hard time.....but, I agree with the others and regardless of how the BF feels this is something that needs to be checked and dealt with..........Good luck!!!!!!!!!