Very sorry to hear about Sweetie
Is she still weeing and what colour is the wee?
No poos for 24 hours - think back to when you last saw her eating hay/dried food - the average transit time for food in the gut is 13-30 hours for a meal to work it;s way through and in some cases can take two to three days depending upon the type of fibre. My guess is that her food intake reduced dramatically either yesterday or the day before and you are now seeing the results.
However she is now on pain relief and antibiotics yet she is not eating or drinking on her own, has not pood for 24 hours and is very lethargic. From my experience of pigs with UTI's, a UTI on it;s own would not normally cause her to progress like this, which indicates something else may be stopping her eating....In view of the fact she has been lifting her bottom, and clearly doesn;t like being picked up/handled and can;t wait to get onto safe, dry land...... a (potentially large) urethral stone is a strong possibility from my own experience below
My Fleure suddenly stopped eating, had blood tinged urine, and suddenly hated being picked up to be syringe fed and kept trying to jump out of my hands which was very out of character. She spent her day frozen in one place in the cage with spikey fur and wouldn;t let Grommie her cage mate anywhere near her and didn;t like to be moved or disturbed . Luckily I didn;t accept my regular vets "wait and see" diagnosis - I booked her in the following day with a new vet (with experience in rabbits and offering a regular sunday surgery) who without any prompting did an X ray there and then (albeit under GA) removed a large stone from the urethra at the same time. With metacam, baytril and syringe feeding for a few days afterwards she was soon restored to her former self.
The most important thing is to syringe feed her critical care/Recovery (20-30 ml every 2-3 hours if you can, particularly tonight) to keep her guts moving and build up her strength and you should start to see poos coming back within the next 24 hours or so. If she is going 12 hours between feeds then that is not good - you need to aim for every 4-5 hours at least in view of the fact her poos have stopped. Also leave some finely sliced cucumber and fresh grass in her cage and maybe she will help herself to this.
Metacam opened about 6 weeks ago should be fine - just make sure you shake the bottle each time and seal it properly after use as it does thicken up when exposed to air. Give the metacam after some liquid feed so it doesn;t go on an empty stomach.
I would ring your vet tomorrow morning and discuss the possibility of getting an X ray done without any further delay to check for urethral, bladder and kidney stones. In Sweetie's case this really should be done without GA as she sounds as though she is too unwell but you may be forced to make a choice.
I would also suggest that at the same time her lungs are checked for excess fluid on the X ray and she is examined for possible heart problems just to cover all the bases. (Are her feet at all swollen, are her lips or ear margins tinged blue, is she breathing heavily from her abdomen rather than her chest? Heart and kidney issues tend to go together as one puts a strain on the other). If (and this is a very big if) they find fluid in the lungs or heart issues (providing there are no kidney stones) then fortekor 1.0mg/kg and fruseamide 2.0mg/kg as a twice daily dosage would hopefully bring back her "perkiness" although she would need a first dose of 5mg/kg of fruseamide to kick start the fluid removal
A speedy diagnosis and treatment are obviously key here (hence why I put on the info about lung and heart issues for your vet) as the longer the problem isn;t addressed, the weaker she will become which is why it is imperative you keep syringe feeding her at regular intervals.
I do hope she makes a full recovery
x