Bladder Stones

Bladder stones, also called uroliths, are hard mineral clumps that form inside the bladder when certain substances in urine become too concentrated and crystallize together instead of staying dissolved. They range from tiny gritty specks to smooth, marble-sized (or even larger) stones, and a pet can have just one or a whole handful at once.

The two most common types in dogs and cats have almost opposite causes, which is part of why treatment isn't one-size-fits-all. Struvite stones, made of magnesium ammonium phosphate, most often form because of a urinary tract infection: certain bacteria produce an enzyme that changes the urine's chemistry in a way that lets struvite crystals clump together. In dogs, normal dog urine is slightly acidic and struvite stays dissolved as long as the urine is acidic and not too concentrated, but if it becomes too concentrated or turns alkaline, struvite crystals will form. The good news is that struvite stones can often be dissolved without surgery. These stones can be dissolved medically by treating the underlying urinary tract infection combined with feeding a special dissolution diet. The process generally isn't quick, though: dietary treatment works by changing urine pH and reducing minerals, and usually takes six to twelve weeks with strict feeding and regular rechecks.

Calcium oxalate stones behave very differently. They tend to form for metabolic reasons rather than infection, and unfortunately they cannot be broken down with food. Calcium oxalate, urate, cystine, and silicate stones cannot be dissolved and require surgical treatment. Certain small breeds seem more prone to them: Miniature Schnauzers, Lhasa Apsos, Bichon Frises, Pomeranians, Shih Tzus, Maltese, Miniature Poodles, Yorkshire Terriers, and Chihuahuas are among the predisposed breeds. Even after surgical removal, owners shouldn't assume the problem is solved for good, since strict compliance with prevention diets and regular monitoring is needed, and even then recurrence rates for calcium oxalate stones remain high. Cats have their own pattern too, with calcium oxalate now accounting for a large share of feline stones alongside struvite.

Whatever the type, the warning signs tend to look similar and easy to mistake for a simple bladder infection: straining to urinate, blood-tinged urine, frequent trips to the litter box or outside with little produced each time, and sometimes crying out while urinating. This overlap is exactly why a vet needs to run tests such as bloodwork, urinalysis, and imaging like X-rays or ultrasound before deciding on a plan, since the right treatment depends entirely on stone type, size, and whether the urethra is blocked. A blocked urethra, particularly in male cats, is a genuine emergency that needs immediate veterinary attention rather than a wait-and-see approach.