It starts with the cat trying desperately to urinate, constantly, in and out of the litter box. The symptoms are unmistakable, and it can be treated very successfully if you take the cat to the vet immediately. It can reoccur but by then you know the medication to use. Delay can cause death. It is good policy if you suspect your cat may be ill to contact your vet.
Many illnesses are easily treatable if only the vet sees the cat early.
Changes in behavior, eating habits, stool habits, urination and vitality are reasons to consult a vet. Diet plays a part in this problem. If you catch it early it is easy to control or be rid of. Just take a Q-tip or cotton ball and wet it with hydrogen peroxide. Wet the cats chin with this thoroughly and clean off all the black marks.