03/09/2025
🚨 BREAKING NEWS in Pet Health 🚨
The University of Minnesota Urolith Center has just identified a new type of bladder stone in dogs – never reported before. 🐾
The University of Minnesota’s Urolith Center (UMN) has identified a new type of canine urinary stone: calcium tartrate tetrahydrate (CTT). In an April 2025 report, Dr. Jody Lulich and colleagues analyzed over 318,000 dog bladder‐stone samples and found 63 cases of this novel urolith (≈0.02% of submissions).
Chemically, CTT is a calcium salt of tartaric acid – a compound normally found in grapes and wine – combined with water molecules. (Tartaric acid is poorly metabolized and is excreted in urine, making it prone to crystallize with calcium.)
Until now, tartaric acid hadn’t been seen in canine stones except in rare rodent studies, but the UMN team confirmed CTT stones in dogs by infrared analysis.
* What are uroliths? Bladder stones (uroliths) are “rock-like” mineral deposits that form in a dog’s urinary tract. Common types include calcium oxalate and struvite; CTT adds a new mineral type to this list.
* Prevalence: CTT stones were very rare – only 63 dogs out of ~318,147 submissions (0.02%) had CTT components. Of these dogs, 84% were male and most were small purebred breeds (~76% purebred). The average age was about 10 years.
* Stone composition: Most CTT uroliths were entirely (100%) calcium tartrate tetrahydrate (76% of stones). Some mixed stones had a CTT core with other minerals outside.
* Dietary link: Strikingly, 96% of cases where diet/supplement data were available had exposure to choline bitartrate – a tartaric acid salt – in the weeks before stone formation. This suggests choline bitartrate (a common supplement ingredient) as the culprit.
Dietary Sources – Choline Bitartrate
The likely trigger for CTT stones is choline bitartrate, which supplies tartaric acid (the “tartrate” in CTT) and choline. Choline bitartrate is widely used in pet nutrition: for example, many homemade or “fresh” dog food plans include a nutrient mix containing L‑choline bitartrate to ensure adequate choline.
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In the UMN study, 20 of 29 dogs (with diet info) had eaten commercial diets that listed choline bitartrate as an ingredient, and 4 of 6 dogs on home-cooked diets received supplements containing it. In short, most CTT dogs had gotten tartaric acid from choline bitartrate.
Veterinary diets and even some medications can also contain tartrate salts (e.g. capromorelin tartrate or trimeprazine tartrate), but in this study the overwhelming source was choline bitartrate in foods/supplements.
* Common choline bitartrate sources: Prescription or fresh dog foods and homemade diet supplements often list “choline bitartrate” as a vitamin source thefarmersdog.comscribd.com. (For example, some DIY diet formulas explicitly include L‑choline bitartrate in their nutrient mixes thefarmersdog.com.)
Pet owners preparing home-cooked meals or using supplements should check labels for this ingredient.
Radiographic and Surgical Findings
Figure: Radiographic and gross images of CTT bladder stones. The radiograph (left) shows multiple radiopaque (bright) stones in a dog’s bladder, which were later removed and identified as calcium tartrate tetrahydrate (right).
CTT stones are radiopaque on X-rays – meaning they appear white/bright on an abdominal radiograph. In the study’s examples, affected dogs often had multiple bladder stones with an irregular contour (unlike smooth spherical stones). Indeed, the UMN report notes all retrieved CTT stones were radiopaque. In surgery or on urolith analysis, the new stones are brittle and consist of fine white crystals.
Clinical Implications and Recommendations
Because choline bitartrate intake was clearly implicated, veterinarians now recommend investigating and eliminating this ingredient if a dog has CTT stones. In practice, that means reviewing the diet/supplements of affected dogs and switching to alternatives without tartaric acid salts. The UMN team specifically advises pet food and supplement makers to use other forms of choline (not bitartrate) or to remove added tartrate entirely.
In summary, CTT is a newly recognized stone type in dogs, first reported in rodent lab diets and now confirmed in clinical cases. It seems closely linked to diets/supplements containing choline bitartrate.
For dogs with unexplained bladder stones, especially small male breeds on homemade or fresh diets, veterinarians should consider stone analysis. If CTT is identified, increasing hydration and switching diets away from tartaric acid sources can help prevent recurrence.
The new finding highlights the complex role of diet in stone formation and will guide future nutritional recommendations for at-risk dogs.
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