Urinary Tract Inflammation

Probably the most common complaint we hear about indoor cats is in regard to inappropriate urinations. “Going outside the box” (or “ectopic urinations” in medical jargon) is a very common syndrome in cats.

In very broad terms, when I’m presented with a cat with ectopic urinations the first thing I try to establish is whether there is a physical problem, or whether it’s a psychological issue with the cat, e.g. marking behavior.


The most common physical problem that causes ectopic urinations is UTI. Everyone who hears that immediately thinks, “Oh yeah, a urinary tract infection,” but I always make a special point to explain to owners that UTI should more accurately be thought of as Urinary Tract Inflammation, not Urinary Tract Infection.

When a cat is urinating outside the litter box due to physical problems, it’s most commonly because of urinary tract inflammation. It’s the inflammation in the urinary tract that makes the pet uncomfortable, and makes it burn when they urinate. Often times they associate this pain with the litter box, and thus tend to avoid the box. Other times, they go outside the box in a futile effort to try to relieve the discomfort, figuring anything different has to be better than the status quo.

Other signs of urinary tract inflammation include very frequent urination efforts with little production, vocalizing while going, and sometimes even blood in the urine. So it’s important to recognize that inflammation of the bladder wall is the reason for all of these signs.

Diagnosing a UTI

The primary way we diagnose urinary tract inflammation is with the standard urinalysis (UA). With it we can view the types of cells and crystals in the urine. Inflammatory cells (usually white blood cells predominantly along with a lot of red blood cells) are numerous, and sometimes there are increased epithelial (bladder wall lining) cells. The UA also usually gives us some insight as to the cause of the inflammation.

That being the case, the next question, of course is what’s causing the inflammation in the bladder wall. In the cat there are several very common syndromes:

  • True UTI – Cats can get a true primary urinary tract infection (primary meaning an infection with no underlying cause) just like people do. However, this is much less common than it is in people or dogs, and is never our primary differential until other causes have been ruled out. In dogs – especially female dogs – primary urinary tract infections are extremely common.
  • Crystals in the urine – Termed FUS, or Feline Urologic Syndrome , crystals that form in the urine scratch the wall of the bladder and cause a sterile inflammation, or cystitis. These crystals most commonly form secondary to being fed cheaper brands of cat food.
  • Bladder Stones – Bladder stones form when crystals in the urine coalesce and form solid structures. They’re a natural progression from FUS. Bladder stones are much less common in cats than they are in dogs. In dogs, stone formation is not based on the food that they eat; however, we can use specialty diets to prevent their recurrence once they’ve been eliminated.
  • Feline Idiopathic Cystitis (FIC) – FIC (sometimes termed FLUTD, or Feline Lower Urinary Tract Disease) is a relatively new diagnosis for an old problem in cats. It’s an inflammation in the bladder wall of cats for reasons that cannot be identified. This is extremely common in cats, and we’ll be discussing it at length in future blog posts.

For now, the main thing to remember when your cat goes outside the box is that our first goal is to try to find out if there’s an underlying physical problem, or whether instead it’s purely behavioral. Once a physical condition is confirmed we pursue further diagnostics to try to determine the underlying cause.