Cat Urolithiasis

how are plugs identified? he hadnt any signs of infection or too much blood
in his urine
there were certainly many crystals though, could it be a combination of
the two?

while trying to pass the cathetere the last time, the vet met an obstacle
(she could sense it)
she cleaned the edge of the cathetere and analyzed the contents in the
microscope where many crystals were visible
she believes that the cathetere eventually passed *by* the stone in the
urethra so the catheterization or the acidification (by s/d food) hadnt
had any effect on the real problem. is that possible? i think the
cathetere is quite wide for that to happen

the good thing is that the cat is in good shape, he is almost used to the
procedure (he was even once catheterized without sedation) and he was
never anorexic. oh and he peed quite a bit after coming home from the vet
today..
is it possible his current difficulty to urinate to be due to urethra
inflammation and not stones?
i'm still having second thoughts about PU but am i just putting off the
inevitable?