Veterinarian Reviewed on January 4, 2008 by Dr. Janice Huntingford
Zinc Toxicity, although uncommon, can develop into a potentially fatal blood disorder. Pets, more commonly young dogs, may ingest items containing zinc such as pennies minted after 1982, batteries, galvanized metals, fungicides, zinc containing shampoos, diaper rash ointments and sunscreens. In contrast, cats very rarely, if ever, suffer from this disorder possibly because their feeding habits are different from dogs.
A toxic dose could involve ingesting as few as one to three pennies (50 to 100 mg/kg). In acute Zinc Toxicosis the amount of zinc absorbed can vary from patient to patient. An acidic environment increases the absorption of zinc. If the pet ingests a meal before ingesting the object, then zinc leaching is reduced.
Zinc Toxicity may show three characteristics: intravascular hemolytic anemia, gastrointestinal upset, and potential multi-organ failure. Zinc irritates the stomach lining and may induce oxidative damage that interferes with the copper and iron absorption from the intestine and the eventual red blood cell production. The result may be marked Heinz formation that indicates oxidative damage and hemolytic anemia, an abnormal breakdown of red blood cells that exceeds the production of new red blood cells by the bone marrow. This disorder can also cause gastroenteritis, inflammation and possible necrosis of the liver, kidney and pancreas.
Symptoms and Diagnosis
Symptoms of Zinc Toxicity include vomiting, red or brownish orange urine, diarrhea, loss of appetite, lethargy, anemia, icterus (yellow skin and mucus membranes of jaundice) and liver failure or kidney failure.
For diagnosis the veterinarian may order a complete blood count, serum biochemical profile (for jaundice and kidney failure), urinalysis, abdominal x-rays and a serum zinc level. Veterinarians need to rule out any confusion with acute gastrointestinal episodes or immune-mediated hemolytic anemia or blood parasites. The zinc-containing object may not show on an x-ray if the animal has already vomited or eliminated the object. Toxic levels of blood zinc are greater than .7 mcg/ml.
Treatment of Zinc Toxicity should aim to remove the source of zinc ingested and to offer support. Items such as pennies, small batteries and other items with zinc components need to be retrieved from the gastrointestinal tract. The veterinarian can use endoscopy to evaluate the gastrointestinal tract for esophageal, stomach and intestinal disorders. A flexible endoscope passes through the pet’s mouth. Performed under general anesthesia, this procedure can remove foreign items without surgery in the stomach area. Surgery may provide another option.
Treatment also involves maintaining hydration, acid-base status and electrolyte balance. Monitoring for anemia includes administering intravenous fluids, a blood transfusion, or gastrointestinal protectors. Another option is chelation therapy that administers chelating agents to remove heavy metal and decrease the toxic zinc blood levels.
Pet owners can provide home care through the careful administration of prescribed medications. Should the pet suffer from vomiting or diarrhea, owners can offer a bland diet. Precautions include preventing chewing or ingestion of zinc-containing items commonly found in the home: coins, hardware, travel cages, certain lotions, ointments and shampoos.
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Janice Huntingford, DVM, has been in veterinary practice for over 30 years and has founded two veterinary clinics since receiving her Doctor of Veterinary Medicine at the Ontario Veterinary College, University of Guelph. She has studied extensively in both conventional and holistic modalities. Ask Dr. Jan