Decoding the Foul Odor Coming From Your Senior Dog

What Could Be Behind a Sudden Rotten Smell in an Older Dog?

"I have a 17-year-old Rat Terrier, and she has lost a lot of weight but eats pretty well; she drinks, pee, and poops. She's been wormed and vaccinated this year but had recently started to smell terribly bad, like really nasty. Dead chicken bad! What's wrong with her?"—Twilla

Potential Causes of Bad Odor in Senior Dogs

A dog of that age might start smelling bad for a number of reasons, such as:

• Dental problems: This is the top reason a dog shows up with a bad smell. Often, a tooth has decayed under the gum, and the odor comes from a hidden pocket of pus. When she grooms, she spreads that smell over her coat, so you notice it even with her mouth shut. Also, even if she's eating, her body burns extra calories fighting the infection, so without extra food, she'll lose weight.
• Cancer: Tumors can grow quickly, and sometimes the blood supply can't keep up, causing them to rot from the inside. This might be in her mouth, which is why you haven't seen it, or you might find it during a belly rub. Some cancers have a distinct odor (1), but you likely wouldn't notice unless the tumor is infected; the smell you describe sounds more like an infection.
• Kidney disease: Bad breath is one sign of kidney disease, but it's usually described as fishy, not like rotting chicken. A blood test is needed to confirm. Weight loss can also occur with kidney disease, so get this checked soon. There's no cure once the kidneys fail, but with some changes, you can keep her comfortable for years.
• Anal sac infection: If your dog is scooting her butt on the carpet, that suggests impacted anal sacs. They can get infected, smell awful, and require treatment.
• Rotting object in the mouth: I see this more in puppies and young dogs that chew things, not usually in a dog her age. If you open her mouth and the teeth look fine, check the roof of the mouth for something stuck between teeth and rotting. If she no longer chews sticks or bones, this is less likely.
• Infection with secondary maggots: This is quite unlikely in a Rat Terrier, but we see it in older long-haired dogs (like Poodles and Chows) with diarrhea. Flies are drawn to feces stuck in the hair.

In a small senior dog, dental disease would be my first guess, but without an exam, there's no way to rule out the others. Take her to your vet, who will check her mouth first. Given her age, x-rays might be needed to see how deep the infection goes, and blood work to check organ function before anesthesia is likely.

This isn't an emergency, but you should call for an appointment right away. A dog with dental disease is in significant pain, even if she doesn't show it.

Source

1. Sharma A, Kumar R, Varadwaj P. Smelling the Disease: Diagnostic Potential of Breath Analysis. Mol Diagn Ther. 2023 May;27(3):321-347. i.nlm.nih.gov/pmc/articles/PMC9893210/

This article is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from your veterinarian. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

© 2024 Mark dos Anjos, DVM