Cats with lower urinary tract problems may go to the litter tray often, strain, cry, lick around their genitals or pass small amounts of bloody urine. With a complete urinary blockage the cat cannot empty its bladder at all. The condition is seen mainly in male cats because their urethra is narrower, but urinary symptoms in any cat need to be taken seriously.
When urine cannot leave the body, it is not only the bladder that is affected. The pressure and changes in the body's salt balance can quickly become dangerous. The cat may seem restless at first but later become lethargic, vomit or collapse. A urinary blockage cannot be reliably told apart from other urinary problems at home.
If your cat makes repeated attempts to pee and nothing, or almost nothing, comes out, seek emergency veterinary care. Do not wait until the next day, and do not try to press on the belly to empty the bladder yourself.