Sorry we're late getting here

A few Serious Thoughts...

The "assume the position" but nothing happens...
Is often a sign of a Urinary Blockage, or "I want and Need to *pee* - but I can't!"
His bladder might be full, but his urinary tract is *blocked* with a kidney stone or a sand-like plug of tiny crystals...

If the Vet checked him (and not a Vet Tech) - s/he should have mentioned that she felt his bladder and it was empty. This check of his bladder *should* have been done - and from your description of his actions (EXACTLY what Boots did when he was plugged) - I would have thought the Vet would have detected a full bladder and Inserted a Catheter to 1) open the blockage and 2) Drain his bladder.

Think back to What the Vet did and said - DID s/he Check his bladder?????

I was told - Several Times - by two different Vets - that a Urinary Blockage *IS* a Fatal Condition if it is not treated properly within a few hours of the onset....
The bladder becomes full of urine, and the cat cannot pass the urine through the blockage. The bladder fills to capacity, and the Kidneys begin to shut down (stop producing urine) because there's no place to store it (kidney produces the urine, but it gets stored in the bladder).
(Cat is now WAY uncomfortable and frantically trying to *pee*)

It is the shut-down of the kidneys that starts the Really Serious situation - toxins that are supposed to be removed by the kidneys are not removed - and flood the cat's body with those toxins. And the kidneys, once they shut down, often do not recover and resume their filtration and waste removal duties.

Vet told ME - each time the catheter was removed - *I* had to WATCH Boots like a hawk...
Being certain that he actually Produced Urine (wet sand in the box) EACH & Every time he tried...
Straining to go and not producing the 'normal' amount of wet sand (urine) was to be considered a RED-Flag emergency - get him to a Vet within a few hours. He was operated on immediatley after his third plug-up and third catherization.

Cautions:
Don't over-water Tubby if he's not *peeing* and actually eliminating urine... He will want to stop drinking if he's internally "full" and cannot pee.

If he has takin IN water, but hasn't been able to successfully urinate since you saw the Vet this afternoon... *I'd* be worried...

With Boots - he didn't ever drink a "lot", but he'd pee once or twice a day. When he plugged up - I'd notice no "wet sand" for about 24 hours; and then Boots would start the *frantic* try to pee but nuffin's happnin routines...
Three times we rushed to the Vet - and all three times he had a "very full bladder"... Meaning we got there "just in time" !!

I know it's late - but at least ~
Start watching him - Closely!!
I'd suggest putting him "in jail" - locked in a bathroom With a clean litterbox. Check the box every few hours... "No Pee" by morning - I'd be on the phone to the Vet. (In Jail so you don't confuse "his' pee with somebody else's eliminations.) Also check the room - Boots would pee outside the box on occasion - I think he was trying to "tell Dad there's a problem"...

I hope your Vet DID check his bladder and found it comfortably empty - but I'd of thought s/he would have TOLD you this fact.

ALL Tybby's signs & symptoms indicate a Urinary Blockage... Please be SURE that was considered and checked! If in doubt - consider a visit to the ER in the morning - it will only take a minute for a trained Vet to palpate (feel) his bladder and tell you if it's empty, full, or TOO Full.

Again - sorry this is late... Been a busy day here.

GOOD LUCK to Tubby and you, *Mom*.

/s/ Phred