Friday, September 18, 2015

Should we be treating crystalluria in cats?

Cats with signs of lower urinary tract disease should also be encouraged to drink fresh water. Even if, like Hero, they insist on being served filtered water from a glass vessel on the kitchen bench only.

What should you do if a cat has crystals in its urine? (Crystalluria, as it is known in the business). While crystalluria sounds like the sort of affliction that unicorns might suffer from, it’s a real phenomenon in many animal species and a common finding on urinalysis in cats. Often the recommendation is not to do much at all. But a new paper challenges that thinking.

In cats, crystalluria can be an incidental finding, but it is also often associated with signs of lower urinary tract disease.

Male cats in particular are vulnerable to life-threatening obstruction of the urinary tract. I know, I live with a victim of this terrible condition and last year’s Christmas/New Year break was a blurof surgery and hospitalisation.

Crystals are often implicated in lower urinary tract obstruction, e.g. by forming a matrix or little plug which blocks the urethra. But what do you do about crystals when you find them in a cat without obstruction? It would be nice if they weren’t there at all. Urethral mucosa is sensitive tissue, and the penile urethra of male cats is a treacherously narrow passage which can become occluded or obstructed readily.

Crystalluria is much more common in cats consuming exclusively dry food diets – also a risk factor for obstructive urinary tract disease. And one might imagine the capacity for a large load of crystals to irritate the bladder wall.

One of the treatments of cats with lower urinary tract disease is to use a therapeutic diet designed to alter urine pH and dissolve crystals. But one doesn’t want to use these willy-nilly and they tend to use more for cats that have had an obstruction or even uroliths.

A recent case report in the Australian Veterinary Journal describes one cat with marked crystalluria and lower urinary tract signs who responded to treatment with a therapeutic diet. The authors performed repeat bladder ultrasounds. Initially the bladder looked like a veritable treasure trove of crystals, while these disappeared following treatment. This happened on several occasions and each time the crystals disappeared once the therapeutic diet was instated.

Two lessons for me here. One is, in addition to performing a radiograph to ensure there are no nasty stones bouncing around in the bladder, we really need to ultrasound the bladders of cats with lower urinary tract signs to look for this sludge (you can find crystals in a urine sample but the amount does not necessarily correlate to the number in the bladder as it is affected by urine sample handling/processing).

The second is that we probably need to be much more proactive at treating crystalluria per se (which we can do if we look for it first).


Bell ET, Lulich JP (2015) Marked struvite crystalluria and its association with lower urinary tract signs in a cat with feline idiopathic cystitis. Australian Veterinary Journal 93:332-335. Doi 10.1111/avj.12353