We have known for years that grapes are toxic to dogs and can cause kidney failure. But we didn’t know why!
The folks at ASPCA poison control think they have identified the culprit toxin! They described it in a letter to the editor of JAVMA, a popular veterinary journal.
How did they figure it out?
They received a report of a dog who developed kidney failure after eating a couple teaspoons of cream of tartar. They also heard about a dog who ate some homemade playdough and developed kidney failure about a day later so severe she was euthanized. When they examined this dog’s kidneys, they saw pathologic changes similar to what we see in grape toxicosis.
They connected a bunch of dots:
- Homemade playdough contains cream of tartar.
- Grapes have high levels of potassium tartrate, which is the chemical makeup of cream of tartar and tartaric acid.
While potassium tartrate is safe for people, we know that dogs absorb it more readily, and it is cleared by their kidneys.
This compound makes a lot of sense as a toxin. Every veterinarian has had patients who are severely sickened by a small amount of grapes yet have also seen dogs who have ingested a large dose of grapes and are unaffected. I remember a client telling me she fed her Yellow Labs frozen grapes as a treat in the summer. I was horrified. The dogs just wagged their tails at me, as Labs do.
It turns out that grapes have varying levels of tartrate, and different forms of it depending on ripeness, variety and growing conditions. That explains somewhat why we see patients reactions can differ so much!
Additionally, we do not see renal failure when dogs get into grape juice or jelly. It turns out tartrates are removed from grapes when those items are processed.
It also solved another conundrum, one I wasn’t aware of. The ASPCA has had reports of vomiting and kidney failure from tamarind ingestion. Well, it turns out tamarinds contain lots of tartrates too!
If you want to read the original letter, the ASPCA posted it on their facebook page: https://www.facebook.com/aspcaapcc/posts/3875710322466733
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