Horseshoe kidney treatment?

Hi all, I have a very good friend who is suffering from the symptoms of his horseshoe kidney, ie possible retrograde urine flow, obstructions, subsequent infections etc... could anyone tell me where to start in looking for the best renal specialist hospital/consultant/treatment available? He has no GP (as he lives and works abroad) to offer a referral, and only knows that he has this anomoly when diagnosed after he collapsed with recurring 'kidney infections' a few years ago.
Any pointers in the right direction would be very helpfull, I'm not sure where to start to choose a specialist for him.