What Dog Owners Need to Know About CTT Stones

In this article:

• What are CTT stones?
• How do CTT stones affect dogs?
• How common are CTT stones?
• Should I worry about CTT stones in my dog?

You may already know that dogs can develop bladder stones, concentrated formations of minerals found in urine. Also known as uroliths or cystic calculi, bladder stones come in several types, all of which you can learn about in this guide. 

These rock-like deposits range in composition and size, from a grain of sand to larger lumps that pose the threat of creating blockages that leave dogs straining or unable to urinate, which is a medical emergency.

In 2025, researchers from the University of Minnesota announced the discovery of a new, rare type of canine bladder stone composed of calcium tartrate tetrahydrate (CTT).

It’s natural to worry about any risk to your dog’s health, but the good news is that CTT stones are quite rare (.02% of bladder stones assessed)—and, like other types of bladder stone, they are treatable. Here’s what you need to know about CTT stones, what causes them, how they affect dogs, and how veterinarians address them. 

What are CTT stones?

Canine CTT stones were recently discovered by researchers with the Minnesota Urolith Center at the University of Minnesota College of Veterinary Medicine. They detailed this finding in a paper published in April 2025 in the Journal of Veterinary Internal Medicine, where they drew a link between the formation of CTT stones and ingestion of choline bitartrate, a common ingredient found in dog foods, including fresh foods.

However, choline bitartrate’s presence in dog food far exceeds its super-rare presence in bladder stones. Adding cognitive and metabolic health benefits to a diet, choline bitartrate is a generally recognized as safe (GRAS) ingredient that’s commonly used in commercial dog foods.

How do CTT stones affect dogs?

Like other, more common types of uroliths, CTT stones may either pass on their own or, if they’re larger and possibly obstructive, require veterinary intervention in the form of surgery. 

Signs of bladder stones may include: straining to urinate, blood in urine, whimpering while urinating, or frequently urinating in small amounts. If you suspect bladder stones, or notice any unexplained change in your dog’s behavior, call your veterinarian.

How common are CTT stones?

CTT stones in dogs are exceedingly rare. 

The University of Minnesota team analyzed 318,147 canine bladder stones between January 1, 2020 and December 31, 2024. CTT was identified in stones from only 63 dogs, or 0.02% of those assessed. 

Of these dogs, the most represented breeds encompassed eight shih tzus, six Pomeranians, six Chihuahuas, six Maltese, six Yorkshire terriers, and six miniature schnauzers, all of which have known predispositions to form calcium-based urinary stones according to previous research. These stones were also more prevalent in male dogs, with 84% of CTT stones originating from males.

To better understand potential causes of CTT stones in these dogs, the team requested additional information from their owners, including information about diet; 33 completed surveys were returned, 29 of which detailed the dogs’ diet prior to urolith diagnosis. Seventeen commercially formulated diets were fed to 23 of these dogs, but only 12 diets contained choline bitartrate, fed to 20 dogs in all. In other words, even among this tiny group, not all the dogs who developed CTT stones were fed a diet containing choline bitartrate.

Should I worry about CTT stones in my dog?

CTT stones are quite uncommon in dogs, and in the study’s context only a small subset of an already high-risk group of dogs had them. Since these stones have only just been identified in dogs, there’s still much research to be done on how to best prevent and treat them. You should always ask your veterinarian any questions about your dog’s health—they’re the most qualified to weigh their history and risk factors—but the prevalence of CTT stones is infinitesimally low, and they are very unlikely to arise in most dogs.

Dog owners can also take steps to help prevent bladder stones in general. A complete and balanced diet can support balanced pH levels in your dog’s urine, and a urinalysis test at the vet can verify this balance. Keeping your dog hydrated with fresh water can also help reduce the likelihood of developing stones.

If you’re worried about your dog’s risk for bladder stones, CTT or otherwise, consult your veterinarian. They’re your best, most qualified partner in keeping your best friend healthy.

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