Greetings all from a newbie with a problem

Well , a little background to start out with . My grown daughter got into boxers with a great looking brindle male named Tyson while she was temperarily living back home. So I was the alpha male of his pack for his first 7months. I had no Idea how much differant boxers are from other dogs, they think they are human and get you believing it .
 When my daughter got back in her own place ,she got Tyson a sweet little fawn female.
And as planned she allowed them to have one litter, 2 white males,1 fawn female a brindle twin to Tyson & a brindle female. I had to have one of course and took the white male with one brindle ear. PATCH  
Patch is 10 months old and has been great from the start, until a few days ago . He acted like he just ran out of gas, ate a good meal the evening of 5-23  and the next morning had diarrhea and wouldnt drink or move unless I left the room , he would slowly follow.
Took him to the vet ASAP. Vet says he has kidney infection Bad. Puts him on an IV for fluids and antibiotics. He's responding well and I should be able to get him home after the holiday weekend.  The vet cant give me a cause or reason why this happened. Any Ideas??
All of Patchs buddies and siblings that he has contact with are all fine. I"m  worried that he could get in trouble again.
Sorry for being so long winded , and putting this here instead of the health page
      Any and all Ideas and replys wil be greatly appreciated.

        JTMAX aka John