Pie Plant Poisoning in Dogs

Rhubarb (Rheum rhabarbarum) also known as the pie plant, is a herbaceous perennial with fleshy red stalks and large triangular leaves. Although the soluble calcium oxalate crystals are most concentrated in the leaves, all parts of the pie plant contain the irritants. Both soluble and insoluble oxalate crystals generally cause intense pain and swelling when chewed or swallowed. This inflammation, combined with the unpalatable flavor, prevents most animals from doing more than sampling the plant. On rare occasions, the dog may ingest more substantial quantities of plant material. On those occasions, your canine companion will require an emergency visit to the veterinarian’s office.

Rheum rhabarbarum, known more commonly as rhubarb or pie plant, contains soluble calcium oxalate crystals which can cause intense pain and irritation in the mouth and when absorbed can cause liver failure.

The pie plant, or rhubarb, contains soluble calcium oxalate crystals in every part of the plant, but they are concentrated more densely in the leaves. When chewed on or swallowed these crystals can cause symptoms such as: 

• Bloody urine
• Cardiac arrhythmia
• Coma 
• Diarrhea
• Difficulty breathing
• Difficulty swallowing
• Dilated eyes 
• Excessive drooling
• Hoarseness when barking
• Loss of appetite
• Numbness of exposed area
• Obstruction of the airway
• Pawing/rubbing at the face or mouth
• Renal failure
• Swelling of the lips or tongue
• Tremors
• Vocalization
• Vomiting

Types

Rheum rhabarbarum is a herbaceous perennial with broad triangular leaves and fleshy red stalks. It most commonly known as rhubarb, but is also referred to as a pie plant as the stems are often used as an ingredient for pie. Other types of plants that contain soluble calcium oxalate crystals can include: 

• Starfruit 
• Shamrock (This should not be confused with clover from the Trifolium family, which does not contain oxalate crystals) 
• Wood Sorrel

All parts of the pie plant contain the calcium oxalate crystals that cause the distress. Calcium oxalate is a calcium salt of oxalic acid which produces numbness or irritation to the tissues it comes in contact with. Pets that chew on this plant will usually experience immediate pain and inflammation to oral area and throat when the crystals are embedded in the soft tissues that they encounter. If any plant material from the leaves is swallowed, the irritant can extend to the throat and down through the gastrointestinal tract, causing swelling and severe pain. If the airway becomes blocked by swelling it may cause difficulty breathing, and should be treated as an emergency. Once the calcium oxalate crystals dissolve into the bloodstream, the remaining calcium oxalate molecules bind with the calcium, removing it from the patient’s system. This sudden drop in calcium can have a destructive effect on the kidneys.

If your canine consumes any part of the pie plant, initial symptoms of exposure to the calcium oxalate crystals will present right away, making an accurate identification of the plant adequate evidence to make a preliminary diagnosis. In cases where the animal swallows the leaves without chewing first, symptoms can take up to two hours to appear. If you witness your pet ingesting the leaves of the pie plant, a visit to the veterinarian’s office for bloodwork and supportive treatment will be needed.

If the source of the toxicity is unknown, your dog’s doctor will take particular note of any opportunities for inappropriate eating as well as any supplement or  prescriptions that are being administered to your dog. A biochemistry profile, complete blood count (CBC), and urinalysis are likely to be ordered at this time, which will help provide a definitive diagnosis when the oxalates are found in the blood or urine. These tests will also contribute to uncovering any concurrent disorders and assessing renal function.

Rinsing the mouth and affected areas with cool, clear water is the first step to removing as much of the plant and its sap as possible. Your dog may also appreciate something cold to eat or drink to alleviate the pain until you are able to contact your veterinarian for further instructions. In most cases, the unpleasant taste and discomfort prevent most canines from ingesting too much of the actual plant material. In mild cases, rinsing the mouth area may be all that is required to treat the pain and swelling. When more significant symptoms appear, your veterinarian will most likely recommend an appropriate pain reliever or antihistamine as well. 

When sizable amounts of plant material have been consumed, a visit to the veterinarian’s clinic becomes probable. IV fluid treatment will be administered when your pet is admitted to the clinic, in order to prevent dehydration as well as to provide support for the kidneys. If an antihistamine was not administered prior to the visit, it may be dispensed at this time as an intramuscular injection. Gastroprotective medications may also be recommended to protect the lining of the stomach from the irritants. Calcium-rich foods such as milk or yogurt are often recommended for the patient as it helps to bind oxalates before they are able to enter the bloodstream. If the airway is dangerously swollen, your canine may need to be kept under observation at the clinic until the swelling subsides.

Dogs that have sampled just small amounts of plants containing soluble calcium oxalate crystals usually have a good prognosis. Minor effects of the crystals as confined to the oral cavity usually dissipate within twelve to twenty-four hours from the initial exposure, however, any swelling that occurs in the throat should be evaluated by a veterinarian. Greater quantities of this toxin usually cause permanent damage to the kidneys. Fortunately, consumption of significant doses are rare due to the initial pain and discomfort that occurs in the mouth. Your canine’s doctor will most likely recommend increasing the monitoring frequency in regards to the viability of your pet’s kidneys.