Everything these days seems to have some sort of battery. Smoke detectors, hearing aids, computers, mobile phones, remote controls and even car keys all have batteries. Unfortunately, batteries are extremely toxic to animals. Most batteries contain a strong acid or alkaline material that will burn any tissue it contacts. Some batteries emit an electrical current that causes severe electrical burns. Batteries may also contain heavy metals such as zinc, mercury and lead which are poisonous.
When I examine a dog for possible battery toxicity, I start with a thorough physical exam paying special attention to the mouth. If the ingestion is recent, I often see a black chalky material in the mouth. I also look for ulcers which are areas where the normal gingiva is burned away exposing the underlying tissues. Next, I take X-rays of the entire gastro-intestinal tract of the animal. Because of the metal, batteries show up well on X-rays. In my experience, dogs who bite a battery will usually spit it out without swallowing any of the battery.
Treatment centers around removing the battery and then treating the damage. In most cases, I do not induce vomiting for fear of causing more burns to the esophagus, stomach or mouth. Instead, I remove the battery as quickly as possible through surgery or endoscopy then I treat the patient with anti-ulcer medications, analgesics to help with the pain and a special diet.
If you think your pet may have ingested batteries, please bring them to a veterinarian right away. Waiting may cause gastro-intestinal ulcers to perforate.
Source:
-Lee, Justine A. Top Ten Small Animal Toxins: Recognition, Diagnosis, Treatment. ACVIM 2010 Proceedings