Calcium oxalate plant toxicosis in dogs & cats | VETgirl Veterinary CE Podcasts

In this VETgirl online veterinary CE podcast, we review a common plant toxicosis seen in both dogs and cats: insoluble calcium oxalate containing plants. We’ll also review the less common plant toxicant soluble calcium oxalate containing plants and discuss the difference between the two types.

When it comes to pet poisonings, plants comprise one of the top 10 small animal poisonings seen at the ASPCA Animal Poison Control Center (APCC).a While there are thousands of poisonous plants out there, the majority of plants typically just result in gastrointestinal signs, including the insoluble calcium oxalate containing plant. That said, a few can be life threatening (such as lilies, sago palm, blue-green algae, etc.) and veterinary professionals need to be aware of the range in toxicosis of certain plant toxins. We’ll cover those in a future VETgirl podcast!

One of the most common plant exposures to dogs and cats are from the Araceae family, of which there are over 200 species.1 The most popular example of this common houseplant is the Dieffenbachia or Philodendron, as these plants are hard to kill – they barely require any water, light, or care and even those with a non-green thumb can own these plants. These types of plants contain insoluble calcium oxalate crystals; I always remember “insoluble” as not absorbed well by the body. A few other examples of insoluble calcium oxalate plants include the:1

  • Arrowhead vine
  • Calla lily
  • Dumbcane
  • Mother-in-law’s tongue
  • Peace lily
  • Sweetheart vine
  • Pothos
  • Hunter’s robe
  • Devil’s ivy
  • Umbrella plant
  • Elephant’s ear

These plants contain needle sharp insoluble crystals which are often arranged in bundles called raphides.1 When a dog or cat chews or bites into these types of plants, it releases the crystals, resulting in acute, profuse pain to the oropharynx. Clinical signs of poisoning include hypersalivation, pawing at the mouth or muzzle, anorexia, vomiting, and edema of the lips, tongue, and oropharynx.1 While rare, dyspnea may be seen secondary to severe inflammation and swelling of the laryngeal area (There’s one published case report of a dog requiring a temporary tracheostomy from this by Peterson et al in JVECC). Rarely, ocular exposure can also occur and result in clinical signs of  severe ocular pain, photophobia, and conjunctival swelling. While clinical signs of insoluble calcium oxalate plant poisoning may be dramatic to the pet owner, signs are generally mild and typically limited to the oropharynx. A lot of these plant ingestions can be managed at home by the pet owner, including removal of the plant, flushing of the mouth out with something tasty (like milk, canned tuna in water, chicken broth, etc.) and rarely, ophthalmic decontamination.1 If these plant poisonings present to your clinic, note you do not need to give atropine for the drooling! Simply flush out the mouth, offer something tasty and consider anti-emetics, subcutaneous fluid therapy or one dose of an analgesic, if necessary.

These insoluble calcium oxalate plants have to be differentiated from soluble oxalate-containing plants, which contain oxalic acid and oxalate salts and can potentially result in more serious toxicosis in certain populations of patients. Examples of soluble calcium oxalate-containing plants include: star fruit, common or garden rhubarb, shamrock plant, etc.2 I personally think that soluble plants are more of a large animal chronic toxicity thing, but we’ll talk about it anyway. That’s because when ingested in large enough quantities in small animals, it can potentially result in toxicosis.

Soluble calcium oxalates are present in varying degrees in all parts of the plant. For example, rhubarb leaves are poisonous as they contain these soluble oxalates (don’t worry, the stem is fine). When ingested, the soluble oxalate salts are absorbed from the gastrointestinal tract; they can then bind with the body’s systemic calcium, resulting in an acute hypocalcemia.2 Formation of calcium oxalate crystals can result in nephrosis (similar to ethylene glycol toxicosis) and secondary acute kidney injury (AKI).2 While the likelihood of AKI is generally thought to be rare from soluble oxalate-containing plants, there are published reports of humans (on dialysis) developing acute on chronic kidney injury when ingesting star fruit. Like most plant toxicants, there’s no known toxic dose reported in small animals. So, dehydrated veterinary patients or those with underlying chronic renal failure may be more at risk for soluble calcium oxalate toxicosis, and should be treated more aggressively.2 Clinical signs include weakness, malaise, hypersalivation, gastrointestinal signs (e.g., anorexia, vomiting, diarrhea) and tetany/tremors (secondary to hypocalcemia).2 Once AKI has developed, signs of PU/PD, abnormal urine output, oxaluria, hematuria, etc., may be seen 24-36 hours post-ingestion. Treatment for large ingestions includes decontamination (e.g., emesis induction, one dose of activated charcoal), fluid therapy, clinicopathologic monitoring (e.g., for hypocalcemia, oxaluria, azotemia, etc.), anti-emetic therapy, and symptomatic supportive care.

When in doubt, contact the ASPCA Animal Poison Control Center for life-saving advice if you don’t know how the toxicant works, what clinical signs, or how to treat it!

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