hmm the vet who performed the PU was different than the casual one and she
is much experienced in situations like this (although she found a small
stone during the operation but lost it!!! there goes our chance identify
the exact composition of the stones..)
the casual vet has contacted at least two other vets to get their opinion,
and is much caring, i wouldnt say she is not competent..
i just think that my cat is cursed, the first day he traumatized the wound
with the e-collar and he was bleeding like hell
today the small cathetere got lost inside the opening (the stitches were
cut) and fortunately the vet managed to pull it out

the urine PH was 6 (5-6 hours after the feeding) but maybe there are
stones which take time to dissolve (he's been on s/d for 3 weeks)
the vet is definite about it being struvite.. we had also sent an urine
sample to a microbiologist who found crystals with an ammonium phosphate
compsition

i dont know what else to expect..(hope not a renal failure)