I am glad that the vet found the cause of your frog's swelling. Hopefully there isn't any kidney damage. Bottled drinking water doesn't have the "salts" and other chemicals that frogs need. Reverse osmosis is the typical method of creating bottled water but the process takes away vital minerals. Spring water may not be any better since you don't really know where the water comes from. Most frog keepers use regular tap water with a good quality water conditioner like Stress-Coat.

You may want to print Frog Forum - Basic Frog First Aid for your vet. It outlines treatments for common frog diseases. Good luck and hope your frog gets well soon