The signs of LUTD are usually referred to as lower urinary tract signs, or LUTS. LUTD includes abnormalities in the structure and function of the bladder and the urethra (see figure).
Hematuria, pollakiuria, stranguria, and periuria (urinating outside the litter box) are the characteristic clinical signs of feline lower urinary tract disease (FLUTD).
Feline lower urinary tract disease (FLUTD) is a common reason for cat owners to seek veterinary care. Cats with any disease of the lower urinary tract present with similar clinical signs, such as hematuria, pollakiuria, stranguria, voiding outside the litter box, and/or urethral obstruction.

FLUTD, or Feline Lower Urinary Tract Disease, is a term used for diferent problems that afect a cats bladder and urethra (the tube which carries urine/pee from the bladder to the outer body).
Cats commonly suffer from problems with their urinary system. Feline lower urinary tract disease (FLUTD) is a term used to describe a combination of signs, such as passing urine more frequently, blood-tinged urine or urinating outside the litter tray or with pain.

Furthermore, visual representations like the one above help us fully grasp the concept of Diagnostic Markers For Feline Lower Urinary Tract Disease.
What Are the Signs of Feline Lower Urinary Tract Disease in Cats? If your cat has FLUTD, you might see one or more of the following signs: Urinating outside of the litter box. More frequent urination (pollakiuria).