Thank you for all the suggestions!

Shasta is still penned up in our bathroom. She is urinating in her
litter box, but crapping in the sink, on the rug and in the window
sill :(  Her stools are loose.  She's still active and not in any
visible pain.  She's eating well. Her meds are all used up now, so I
am making her an appointment with another vet. I suspect she may be
getting "cramps" and just releasing wherever she happens to be.

BlueMaxx, I've only seen her eat litter that one time, when she
wouldn't eat the chicken and rice.

Friesian, my cat would crap on TOP of the bed, but she would piss
under the covers.  That's where she would sleep during the day. It was
like she got the urge to pee, but didn't bother to go to the litter
box.

-Tom in Scranton, PA

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In the USA anyway, there is also such a thing as a waterproof mattress
cover. It comes in two styles. (From the time Molly was young, she had slept
with us at night. When she got elderly, she would sometimes "leak" in her
sleep.) The style we got looks like a giant, heavy gauge plastic bag with a
zipper. It completely encases the mattresses and comes in twin, full, queen,
and king. The sheets and blanket go on top. There is another style which
just covers the top and sides of the mattress (like a fitted sheet, but we
didn't like this style as it didn't stay in place as well. The price varies
depending on the size. The zippered style is around $15.00 for the twin size
and around $20.00 for the queen size. They last forever assuming you don't
have a cat who claws them to pieces (then they tear over time). But IMO,
they were worth every penny. Once the cat has urinated on the mattress
itself, you will never get the urine out completely no matter what you do
because the urine soaks in deep. It costs hundreds of dollars to replace a
mattress.
Best regards,
---Cindy S.

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It's not just a matter of households being "different." A house filled with
raw sewage (even without a communicable disease) is a health hazard. And if
a neighbor or guest were to see that, that person would call child
protective services immediately and rightly so. I can guarantee the children
would be removed from the situation and placed in foster care. The health
board would in all likelihood also be called, and (all) the animals would be
taken away as well.

There is a limit to how much cat urine/excrement one can clean up all over
the house. Enzymatic cleaners like Nature's Miracle work well for an
occasional accident, but despite the name, they really can't make "a
miracle." In the last year of Molly's life, she began urinating in the
corner of the living room on the carpeting (she did not have a UTI). Even
though she didn't seem to have any problems going up the stairs (all of our
litterboxes are upstairs), and she came upstairs many other times during the
day, she didn't want to go up to use the litterbox. She decided that the
corner of the carpeted living room was her new litterbox. It took us a while
to discover the problem (her urine was very dilute because she had CRF, so
it lacked much of the telltale cat urine odor). I solved (most of) the
problem by reluctantly added a litterbox on the main floor, in the hallway
outside the kitchen. In spite of this, she still continued to use the corner
of the living room at least some of the time. The net result was that we had
to pull up much of the living room carpeting, and we will additionally need
to replace parts of the (now blackened) hardwood flooring underneath. And
our cat was limiting her urinating to one place. She wasn't going all over
the house. If Molly had been urinating all over the house, there is no doubt
but that I would have confined her to the kitchen full time. No matter what
the reason, you can't allow an animal to turn your home into a toilet and
put your health and the health of your children at risk.
Best regards,
---Cindy S.

That is not what you stated. You stated that she pissed on your bed and that
you once again locked her in the bathroom. A UTI is not contageous. Diet
plays more of a roll in that than anything else. I'm always amazed that when
you call someone out when they say stuff like "We can't keep her if she's
like this all the time" the person suddenly says I have all these children
and such. Cat pee and spots can be cleaned up but to suddenly use the "we'll
dump the cat" bit certainly says that you wish to punish her.

I'm not being overly sensative as you state. I've just seen too many cats
end up at the rescues because people lightly work out the problem and then
say they've spent enough to try and solve the issue. When they urinate
outside the litterbox it is either behavioral or it's medical.

Here is one idea I think you should try, why not put the litterbox in your
bedroon in an area near where she is peeing. Then slowly each week move it
away from the area to a more secure location. You might also keep a toy or
teaser attached to the litter box (mounted on the wall or something) so she
associates it with something pleasent.

You never mentioned how often you scoop the litterbox but if you don't do it
at least 3 times a day then I can see why your cat might go elsewhere if the
problem isn't a UTI. BTW, does this cat or any of them for that matter cry
or yowl when they use the litterbox and are scratching around in it? If so,
then I'd say this is a urinary issue and it needs to be treated ASAP. BTW,
if a cat has a UTI it doesn't mean they'll crap in the box while they
urinate elsewhere. They may decide to go in other places to do that. If your
cat in question has crystals in the urine (which you should bring in a
sample into a vet) then you definately need to deal with the issue. One of
my cats has had a UTI off and on and I can say it is very unpleasent but
after getting him on anti-biotics and the right food he's been much better.