Obviously I haven't seen your kitty, so it is impossible to guess what's going on thru the forum, but I thought this might help a little.
The three most common causes for sudden, inappropriate urination are:
1) UTI's (urniary tract infection)
2) crystaluria (having crystals in the urine because of an imbalance of the unrine pH), and
Cats can have very hard to detect UTI's and can sometimes only be diagnosed with a culture of the urine. But, crystals in urine are tough too.
They can get crystals in the urine if the pH is too high or too low, and this causes irritation in the bladder. Cats often respond by urinating in different places. These crystals are microscopic, and cannot be seen with the naked eye. The danger of these crystals is that if left untreated, they can cause a blockage and keep the kitty (most commonly males, as they have more tubing to get blocked with
) from peeing. You will often see a kitty cry, strain, or go in/out of the box when this is happening. Also if the kitty is lethargic and/or won't eat, there could be a problem. If the kitty is unable to or is producing very little urine, it needs medical attention IMMEDIATELY
, as it is a life threatening condition.
Another risk of crystals in the urine is that they can form bladder stones. Those are dangerous for all the same reasons that crystals are. Those, in a male cat, are almost always surgical.
If it is behavioral, then that gets a bit complicated. Too much to be discussed here, but there are ways to treat it.
Bottom line is that the kitty probably needs an exam and a urinalysis to start with. If there is no straining and the kitty seems ok otherwise, it can likely wait until tomorrow.
But, the sooner the better. If you can, collect the urine that has be voided on the other surfaces and refrigerate it until you can bring your cat in. If not, then try to not let the kitty go before the appointment so that the doctor can get a sample. Good luck and I hope you feline is feeling better soon!