Feline idiopathic cystitis, formerly called FUS and FLUTD is a poorly understood condition in cats, which unfortunately is pretty common and
has a tendency to recur. In fact, about half of the cats with this condition will have at least another episode within a year.
Some or all of the following symptoms may be observed:
excessive licking of the urinary opening
straining to urinate
frequent visits to the litterbox or urinating outside of the litterbox
vocalizing in pain while inside the litterbox
inability to urinate due to a blockage of the urethra
Your veterinarian will want to conduct a urine test and take radiographs, to rule out a blockage, a bladder infection and bladder stones.
Only when all these other conditions are ruled-out, a diagnosis of FIC can be made.
Not one single cause has been identified, but environmental stress and concurrent illnesses seem to play an important part. Younger cats seem to be predisposed to this disease.
The reason why only some cats get it, seems to have to do with the way that they handle stress, and the hormones associated with it. A cascade of events is triggered that leads to
irritation of the bladder lining, pain, bleeding, and urgency to urinate.