The only other thing would be if the dog wasn't getting enough water to drink, and was becoming dehydrated. Also, some dogs can be picky with their water. Google it; I can almost guarantee he has it. However, sick dogs or those with weak immune systems are more susceptible to infections.
Why a Dog Laps Its Own Urine
If you watch your dog lick urine while "savoring" it, pressing their tongue against their palate and raising their snout, it's probably because they are using the vomeronasal organ to receive extra information from a dog in the area. He most likely has Cushing's disease. This can also cause them to develop a preference for it.
Why does my Dog Lick Urine of Other Dogs?
The vet said "you're absolutely right" and we did more testing to determine which kind of Cushing's he had. Forum Dogs Dog General Dog licking his own urine. Also, lock the dog door during the day and watch how often he 'asks' to go outside.