Friday, June 22, 2012

Are these foods REALLY toxic?

By Beth Davidow, DVM DACVECC

There are a number of foods that are now known to be toxic to pets. I tend to wonder each time I hear of a new toxicity, “is that really true?” I often think, “Well, I’ve seen lots of dogs who eat that who haven’t had a problem.” The growing list of toxic foods for pets now includes chocolate, onions, grapes, raisins, and chewing gum containing xylitol (many of the sugar free gums). Although I read these new reports critically, working in emergency, I have now seen all these toxicities first-hand.

Chocolate toxicity has been known to many of us for years. Theobromide, a methylxanthine, is the main toxic component, and causes extremely fast heart rates, tremors, and can lead to seizures. The darker the chocolate, the more theobromide is contained in each ounce and the less the pet has to eat of it to cause problems. White chocolate is actually not toxic at any amount. A 60-pound lab would need to eat 20 ounces of milk chocolate to have moderate to severe signs but only three ounces of dark bakers chocolate. Depending on when the chocolate was ingested, we might recommend inducing vomiting or having us administer activated charcoal. (Activated charcoal binds toxins that are in the stomach or intestinal tract so they can’t be absorbed into the blood stream.) We’ve seen many dogs that presented with agitation and severely elevated heart rates. Most have done well but some needed 24-48 hours in the hospital on IV fluids and medication to decrease the dangerously high heart rates.

Onion toxicity is one I hadn’t seen until a few years ago. Onions and other members of the Allium family (shallots, garlic, and green onions) contain a compound that can weaken red blood cells. The red blood cells break down causing anemia (lack of red blood cells) and hemoglobin (the protein inside red blood cells) to spill into the urine. Dog’s red blood cells have less antioxidants than people’s making their cells more prone to damage. Cats are even more susceptible to red blood cell damage. Ingestion of 5g/kg of onion in cats or 15-30 g/kg in dogs can lead to clinically important hemolysis. Damage consistently happens in dogs who ingest more than 0.5% of their body weight in onions at one time. A few years ago, an English setter was referred to us for inappropriate urination and red colored urine. It turns out he had eaten three cups of onions the day before – 1.5% of his body weight! The red color was hemoglobin in his urine. He became very anemic four days after he ate the onions and needed a transfusion. To complicate matters in his case, he also had a bacterial urinary infection. The combination of the hemoglobin going through his kidneys and the infection, despite antibiotics and IV fluids, led to acute kidney shut down. After 10 days of hospitalization, antibiotics, and IV fluids, he is doing well at home.

Grape and raisin toxicity was first reported by the National Animal Poison Center in 2001. At that time, they knew of 10 reported cases of acute kidney failure with ingestion of quantities varying from 0.2 oz/lb to 4.4 oz/lb. A retrospective study was published in 2005 in the Journal of Veterinary Internal Medicine involving 43 cases. Of the 43 cases, 20 died or were euthanized due to a poor prognosis. Unfortunately, it is still not known why some dogs, but not all dogs, develop acute kidney failure from ingestion of these foods. Pesticides, fungus and heavy metal contamination have been ruled out as causes and it appears that the toxic principle is in the flesh and not in the seed. Last year, we treated a dog who developed acute kidney shutdown after eating grapes off a vine at a friend’s house. The dog survived and is now doing well but was hospitalized for almost two weeks and required subcutaneous fluids for many weeks afterward. We do recommend inducing vomiting, activated charcoal and IV fluid diuresis with any grape ingestion over 0.7 oz/kg or raisin ingestions over 0.1oz/kg. Induction of vomiting is recommended up to eight hours after ingestion in these cases as in many of the cases reported to National Animal Poison Center, raisins were still found in the vomit at this point.

Xylitol is a sugar substitute that is good for people on a low carbohydrate diet, those with diabetes or those watching calories. It is found in sugar free gum, some toothpastes (it can prevent oral bacteria from producing acids that damage tooth surfaces), and can be bought as a powder for cooking. Although the lethal dose is >130 g/day in people and greater than 20g/kg in mice, the metabolism is different in dogs. It appears that doses greater than 0.1g/kg can lead to hypoglycemia 30 minutes to 12 hours after ingestion. This is because in dogs, but not in people, xylitol causes a dose-related rapid, severe insulin release. In addition, acute liver failure and bleeding problems has been reported in eight dogs after eating xylitol containing products. Most of the dogs presented with vomiting and lethargy nine to 72 hours after xylitol exposure. The reason for the liver failure is currently unknown. National Animal Poison Center does recommend vomiting induction, IV fluids, and careful monitoring of blood glucose and liver enzymes.

The NAPCC is a fantastic resource and we recommend that their phone number be easily accessible in your household. The Washington Poison Center now also has a veterinary toxicologist on staff and is also very helpful especially in cases of household chemicals or product exposure. In addition, our emergency doctors are very knowledgeable about toxicities and are always happy to answer questions at any time of day or night. (NAPCC, 888-426-4435 and Washington Poison Center, 800-222-1222)

Monday, June 18, 2012

Gastrointestinal Foreign Bodies

By Beth Guerra, DVM  

In my eleven years as a veterinarian, I have amassed quite a list of objects I have removed from the GI tract of dogs and cats. We veterinarians all have that one item we have pulled from the stomach or intestine that seems unique. I am constantly amazed at the ability of our furry friends to actually swallow these objects. I have seen some spectacular objects pass through with no problem, like straight pins and acorns, but I more frequently deal with patients where the offending object has caused an obstruction. Objects that make it into the stomach have two options; either they will be vomited up or try to leave the stomach through the pylorus. If the object is too big to advance into the intestine, it will remain in the body of the stomach and usually causes intermittent vomiting. Objects that advance into the small bowel will either pass without incident or cause a bowel obstruction.

Patients with GI foreign bodies can have a variety of symptoms, including vomiting, inappetance, or abdominal pain. Some pets will still want to eat but will vomit partially digested stomach contents shortly afterwards. In smaller dogs or cats, the foreign object can often be felt on abdominal palpation. Diagnosis is usually based on x-rays. Some objects, such as rocks or metal, show up easily on an x-ray, but others like cloth can be difficult to visualize, so a diagnosis of obstruction is made based on the appearance of the intestines and gas patterns. Abdominal ultrasound is used in those cases where the x-ray is inconclusive.

A rapid diagnosis and treatment of GI obstructions is ideal, especially when objects are obstructing the small bowel. The longer an object remains in the bowel, the greater the concern for complications such devitalized bowel or intestinal perforation. There can be pressure necrosis, or death of the tissue, over the object. This pressure necrosis can cause the tissue to tear and lead to leakage of intestinal contents into the abdominal cavity. In severe cases, the compromised bowel may need to be resected. If perforation has occurred, the resulting infection in the abdomen, called peritonitis, can be fatal.

Obstructing foreign bodies often need surgery. In some cases where a small, smooth object is in the stomach, the veterinarian may induce vomiting to see if the object can be retrieved. Alternatively, endoscopy can be attempted to pull the object out through the esophagus. If the object is sharp, very large or no longer in the stomach, surgery is indicated. The patient is usually started on aggressive fluid therapy to combat dehydration from vomiting, and in rare cases, this can encourage an object to pass. If the duration of symptoms is more than several days, or if there is concern for bowel perforation, surgery should not be delayed. With prompt treatment, pets often recover uneventfully from these surgeries.

Ingestion of foreign bodies can be prevented by providing your pet with toys that are adequately sized for the breed of dog to prevent accidental swallowing. You should also consider supervising your dog when offering treats such as large rawhides or greenies to make sure the treat is chewed slowly and not gulped down in large chunks. If you suspect that your pet has ingested something inappropriate or is showing clinical symptoms, a veterinary exam is recommended sooner rather than later.