Rhubarb Poisoning in Dogs

Rheum rhabarbarium, commonly referred to as rhubarb, is a herbaceous perennial with fleshy red stalks and large triangular leaves. All parts of the rhubarb plant contain soluble calcium oxalate crystals, although they are concentrated in the large leaves. Oxalate crystals can cause intense pain and irritation when chewed or swallowed. This irritation, combined with an unpleasant taste, usually prevents animals from doing more than sampling the plant. However, some pets will work past the pain as they chew and on rare occasions, a dog may eat larger amounts of plant material. On those occasions, your canine companion will require an emergency visit to the veterinarian’s office to have his health condition checked.

Rheum rhabarbarium, known more commonly as rhubarb, contains soluble calcium oxalate crystals which can cause intense pain and irritation in the mouth and when absorbed, can cause renal failure.

The rhubarb plant contains soluble calcium oxalate crystals in all parts of the plant, but they are most concentrated in the leaves. When chewed or swallowed these crystals can cause: 

• Blood in urine
• Cardiac arrhythmia
• Coma 
• Diarrhea
• Dilated eyes 
• Difficulty swallowing
• Excessive drooling
• Hoarse barking
• Kidney failure
• Labored breathing
• Loss of appetite
• Numbness of exposed area
• Obstruction of the airway
• Pawing/rubbing at the face or mouth
• 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 also goes by the name of pie plant as the stalks are often used as an ingredient for pie. Other types of plants that contain soluble calcium oxalate crystals can include: 

• Starfruit (Averrhoa carambola)
• Shamrock (Oxalis spp), which should not be confused with Trifolium variety of clover, as it does not contain oxalate crystals
• Wood sorrel (Oxalis acetosella)

All parts of the rhubarb 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. Chewing may cause immediate pain and inflammation to the mouth and throat as these crystals are embedded in the soft tissues. If any plant material from the leaves is swallowed, the irritation can extend to the throat and down the gastrointestinal tract, causing swelling and severe pain. The swelling may cause breathing difficulty if the airway is blocked. Once the calcium oxalate dissolves into the bloodstream, it binds with the calcium, effectively removing it from the system. This sudden drop in calcium can have it can have a destructive effect on the kidneys.

Initial symptoms of exposure to the calcium oxalate crystals from rhubarb ingestion will present immediately, making identification of the plant helpful to the diagnosis. If possible, bring a piece of the plant with you when you visit the clinic. In some cases, such as when the dog swallows the rhubarb leaves without chewing first, symptoms can take up to two hours to appear. The ingestion of the leaves of the rhubarb plant will probably prompt a visit to the veterinarian’s office for supportive treatment, therefore, it is not recommended that you wait for your pet to become ill before calling the veterinary clinic. 

A complete blood count, biochemistry profile, and urinalysis are likely to be ordered by the veterinarian upon your arrival. This is done to uncover any concurrent diseases or disorders, to confirm the type of toxin, and to assess renal function. If your dog is experiencing nausea and vomiting, plant material found in the vomit will often confirm the diagnosis.

You may choose to start treatment at home with a thorough rinsing of the mouth and affected areas with cool water in order to remove as much of the plant as possible in an attempt at pain relief. You may want to offer your dog something cool to eat or drink as well, to ease the pain until you are able to make contact with your veterinarian. In most cases, the discomfort and unpleasant taste will prevent most canines from ingesting much of the actual plant material. In those mild cases, rinsing the mouth area may be sufficient in treating the discomfort. In certain circumstances, your veterinarian will recommend giving your dog an appropriate pain reliever or antihistamine as well. 

When larger amounts of the plant material are consumed, or if you are not certain what plant your dog has sampled, a visit to the veterinarian’s office is necessary. Evaluation by a veterinarian is always the wisest choice when dealing with the ingestion of a potentially toxic plant. Once there, intravenous fluid treatment will be most likely given to prevent dehydration and help support the kidneys. This will also help the body to flush out the toxins. If needed, medication to help your dog eliminate the rhubarb plant from the body can be added to the intravenous treatment. Pain relief may be given through the IV if your dog appears overly distressed and uncomfortable.

If an antihistamine was not previously recommended, it might be administered as an intramuscular injection at this time. In an attempt to protect the lining of the stomach, gastroprotective medications may also be recommended, and calcium-rich foods such as milk or yogurt may be offered to the patient in order to help bind oxalates before they can enter the bloodstream. If the airway is dangerously swollen your canine may need to be kept under observation at the office until the swelling subsides.

Prognosis for dogs affected by sampling very small amounts of the plants containing the soluble calcium oxalate crystals is usually quite good. Any swelling in the airway should be evaluated by a veterinarian. However, the other minor effects of the crystals as confined to the mouth area usually dissipate within twelve to twenty-four hours from the initial exposure. Consumption of substantial doses are generally rare due to the initial pain and discomfort in the mouth. Large quantities of this toxin usually leave permanent damage to the kidneys. Your canine’s doctor will most likely recommend increasing the monitoring frequency in regards to the viability of your pet’s kidneys.