I have some answers to questions raised by J.dvm and Phil.

The leukocytes and erythrocytes in her urine are according to my vet "+3",
which she says is off the scale. Meaning, I assume, the strain is virulent.
However, that does not mean according to her it will become systemic or
dangerous. She simply said: No e coli should be in the bladder and we
should kill it. No ifs ands or buts.

After consultation with a vet. internist, the only drug they recommend of
the 4 that might kill this thing is called Trimethoprim-sulfphamethoxazole.
Apparently this drug was pulled from the market for cats awhile ago but we
can get some. Possible side-effect: renal crystalization. Upside: it's
oral, can be done at home. Recommendation: bloodwork, 3 days on, more
bloodwork, continue if possible until we get several negative urine
cultures. Likely length of treatment: 6 weeks, but may be more.

Once this is done, we can try to address the bladder stones; her pH is acid,
so the assumption is that it's an oxylate stone. How we address them is up
in the air, given her chronic renal failure. Switching her off k/d to use
diet to address the stones is problematic; so is, of course, surgery.

Right now I'm very tempted to say: Leave my cat alone. We don't know if her
CRF will accelerate; we don't know if the e coli will become toxic. And
then...she threw up this morning and started straining again, and I start to
panic again. I have no idea what to do.

Any thoughts are very much appreciated.