Cat litter is made of two nontoxic compounds: one a feed additive, and the other the main ingredient in dirt. How can something so innocuous poison your dog? The answer is in the clumping action -- in your doggy's intestines -- so prepare to be amazed and truly grossed out.
Bentonite and Old Dirt
Bentonite is a common clay powder. It is considered so safe it's used as a feed additive for pets and livestock, and in products for humans, too. Silica is what rocks, sand and dirt are mostly made of. Both are considered biologically inert, meaning they don't do much of anything inside a body ... unless they are mixed together. Your kitty's litter conveniently clumps because moisture (from you know where) turns bentonite and silica essentially into cement.
The trouble starts when your doggy gives in to the temptation to eat those tasty feline brownies out of the litter box (yes, it is totally gross). With the poo comes clumps of litter. The litter mixes with the liquid in your pup's intestines and forms a giant blob basically of wet cement. It swells inside your dog so it can't be vomited up or exit through the normal route and gets thoroughly stuck. Thus, all other material (food, gas, poo) gets stuck in front of the blockage. This causes extreme gastric upset, including nausea, vomiting, inability to eat, extreme drooling and head shaking, convulsions and abdominal swelling. Without intervention, a fatal gastric rupture is on the horizon.
Exactly as much fun as it sounds, venous strangulation is when blood keeps getting pumped into the intestine, but the swollen mass of cat litter keeps it from flowing back out. Eventually this causes fluid to leak into the abdominal cavity, which leads to shock, and necrosis -- tissue death -- from lack of oxygen to the strangled tissues.
The only true poisoning from eating cat litter comes from toxins produced by bacteria. Escherichia coli and clostridium are the usual culprits -- the same bacteria responsible for many cases of food poisoning. Your dog can ingest these with the cat feces, or they may already be in the gastrointestinal tract. They cause poisoning when they leach out during a rupture.
Cat litter poisoning is serious business -- a dog with an intestinal blockage has from 4 to 35 hours to live without intervention. If your dog is showing signs of gastric distress and you suspect litter ingestion, get to a veterinarian immediately. Best of all, make sure your pup never has access to where your kitty poos.
- The Merck Veterinary Manual: Gastrointestinal Obstruction
- European Food Safety Authority: Scientific Opinion on the Safety and Efficacy of Bentonite as a Feed Additive for All Species
- American Kennel Club: Cats and Dogs Together - Can They Really Get Along?
- American Society for the Prevention of Cruelty to Animals: Cat Litter
- Science Lab: Material Safety Data Sheet - Bentonite
- George Doyle/Stockbyte/Getty Images