Sources

A wide variety of common house and landscape plants contain insoluble calcium oxalates (IO) in sufficient quantity to cause clinical signs if chewed on or ingested (Table 67-1). Many of the plants most commonly associated with ingestion by small animals tend to have broad, often shiny leaves and do not produce flowers.⁴ The family Araceae contains a large number of plants that are popular as ornamentals and that contain IO. Introduction of these plants to a pet’s environment may result in the pet “exploring” the plant with its mouth, often with painful consequences.

Table 67-1 Common Plants Containing Insoluble Calcium Oxalate Crystals^2,4

Toxicity

Despite the fact that even a single bite of IO plants has the potential to cause immediate and intense clinical signs, many exposures result in no apparent clinical effects in dogs and cats.⁵ The severity of signs is dependent upon the concentration and type of oxalate crystals in the plant and the extent of exposure. Fortunately, immediate pain often results in cessation of chewing, limiting exposure. In humans, ingestion of Dieffenbachia leaves has occasionally been associated with pharyngeal obstruction resulting in potentially fatal respiratory compromise.⁶ A single case report exists of a dog fatality caused by airway obstruction following ingestion of Dieffenbachia picta (dumb cane).⁷ However, because the relatively large pharyngeal area in species such as dogs and cats makes complete obstruction from tissue swelling uncommon, most cases of ingestion of IO plants by these pets are rarely serious or life threatening. A few early anecdotal reports on Philodendron spp. suggested that nephrotoxicity or neurotoxicity was possible, especially in cats, but attempts to reproduce these clinical effects in experimental felines have not been successful.² In canaries, orally administered suspensions of Dieffenbachia leaves resulted in acute death, but no adverse effects were reported when budgerigars were similarly dosed.^8,9