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Bloat: Is your dog at Risk?

By Tamara Aegard

What is Bloat?

Gastric Dilatation Volvulus (GDV), commonly referred to as bloat and torsion can be a devastating way to lose a beloved pet. This condition can sneak up quickly and can end fatally. Affected dogs suffer extreme pain and their abdomen can swell to an immense proportion.

So, exactly what is bloat? It is a series of events. Air (sometimes fluid) accumulates in the stomach and this causes dilation of the stomach. The volvulus (torsion) happens when the dilated stomach twists, cutting off any way for the air to escape. On one end the stomach closes at the esophagus and on the other end access to the small intestine is sealed. The stomach is now effectively isolated. As the condition progresses the ever enlarging, twisted stomach starts to put pressure on the blood vessels. Often these blood vessels will twist as well, hindering blood flow to the heart and lungs. If the flow of blood to the heart is decreased, then an insufficient amount of blood is reaching the rest of the dog's body. Soon tissues are deprived of oxygen, and undergo necrosis (this is especially true of the stomach wall). Death soon follows.

An early sign of bloat is usually a restless dog. They may pace continually, or get up and then lie down only to repeat the process. Excessive salivation is often noticed, as well as panting and unsuccessful attempts to vomit. As the condition continues the abdomen noticeably swells and feels tight like a drum. (It is important to note that not all dogs that bloat have a distended stomach) The dog will then go into shock (weak, pale gums, shallow pulse) and then into a coma with death as the ultimate outcome if the condition goes unnoticed or untreated. The fatality rate of GDV runs at about 29%.

Who is uncovering the etiology?
It would stand to reason that since GDV is a leading cause of death in giant and large breed dogs that there would be substantial research into the causes for this disorder. But this is not the case. Dr. Larry Glickman of Purdue University is one of only a handful of researchers investigating the causes of GDV. Most studies deal extensively with treatments and not the actual cause. Before Dr. Glickman became a researcher and teacher at Purdue University he held faculty appointments at Cornell and the University of Pennsylvania. Most importantly he is a pioneer in applying epidemiological methods to study pet dogs. He was the first to show some breeds were more susceptible to parvo-virus infection, and that exposure to asbestos and pesticides increased the risk for specific types of cancer. He has been the recipient of numerous awards and has authored over 175 scientific articles on canine health. His most recent research was undertaken to isolate risk factors in order to identify environmental situations and characteristics that make dogs more susceptible to GDV. In this study he followed nearly 2,000 dogs belonging to 11 breeds for up to five years to determine which would develop bloat and which would not. He then took all the data he had accumulated and related it back to things like the breed of dog, size, shape, personality, age, genetics, diet and how the dogs were managed. Analysis is still ongoing.

Breed Level Analysis
In the first part of the study Dr. Glickman tried to look at characteristics that would put one breed at a higher risk for GDV than another. He characterized large breed dogs as those that weighed between 50 and 99 pounds at adult weight and giant breed dogs as weighing more than 99 pounds as adults. He did not study smaller breeds as they are not as prone to bloat. He included 11 breeds, chosen because they were well known to be at high risk for GDV (Akita, Bloodhound, Collie, Great Dane, Irish Setters, Irish Wolfhound, Newfoundland, Standard Poodle, Rottweiler, St.Bernards, and Weimaraners). Though Labrador Retrievers were not included in this study the results are still valuable and can be applied to all breeds. The dogs used were measured at AKC shows and breed size, breed shape, temperament, aging and genetics were the characteristics analyzed. As an aside, a purebred dog is 3 times more likely to bloat than a mixed breed.

BREED SIZE- Glickman found the incidence of bloat was high and nearly identical between large and giant breed dogs. Fatality rate of those that developed bloat was 29%. The highest risk dog was the Great Dane with a 42% risk of bloat in their lifetime. From previous studies Labrador Retrievers have a 2% risk of bloat. For large breed dogs in the study the rate of GDV was 23% and for the giant breed dogs the rate of GDV was 26%.

BREED SHAPE- According to Glickman breeds that have a deeper and narrower abdomen are at greater risk. The abdomen depth/width ratio is a much stronger predictor than the chest depth/width ratio for GDV. He thinks the deeper and narrower the abdomen, the greater the room for the stomach ligaments to stretch down or lengthen as part of the aging process. So the deeper abdomen provides more room for the stomach to actually descend with age. Glickman thinks the combination of stretched ligaments and greater room allows the stomach to twist.

TEMPERAMENT- Glickman found that personality turned out to be a great predictor of GDV at the breed level. Owners were asked to rate their dogs on a scale of 1 to 10 for traits such as aggression to people, aggression to dogs, submission to people, submission to other dogs, excitability, fearfulness, happiness, trainability and whether dogs were easily upset by new situations. Two very clear trends emerged says Glickman. The more fearful the breed, the higher the risk of bloat, and the more easy going the breed, the lower the risk. Glickman also points out that it is not the amount of stress a dog experiences but how the animal's body reacts to it. He says when animals are put under stress certain stress hormonal and neuronal responses occur. And some of these responses clearly affect gastric motility. So, a fearful dog may have a very different response physiologically to stress than a happy dog. He thinks those physiological responses may contribute to the rotation of the stomach because of the gastric motility.

AGING- Dogs of all ages were included in the study. Not surprisingly, Glickman found that the incidence of GDV increased with advancing age. As with most diseases, bloat can occur at any age but the rate increases as the dog ages. Glickman says this means we have to think about how bloat ties into the aging process. In large breed dogs the incidence of GDV increase dramatically after 3 years of age. In giant breed dogs the increased incidence starts significantly earlier.

GENETICS- Glickman does not believe bloat is genetically based in the sense that one gene causes bloat, but the inheritance of certain traits and characteristics predispose breeds or individual dogs to bloat. His strongest recommendation to prevent GDV is to NOT breed a dog that has a first-degree relative that has had GDV. Results of this study suggest that the incidence of GDV could be reduced by approximately 60%.

Individual Dog Analysis
In the second part of the study Glickman looked at individual dogs to see why those dogs were at increased risk compared to other dogs in the study. Risk factors that were analyzed included gender, neutering, weight, diet, speed of eating, belching and flatulence and genetics: and environmental factors such as housing, restriction of water/exercise around feeding time, elevated food bowls, moistening food, preventative medication and number of meals fed.

GENDER- Glickman found only a minimal difference in the risk of GDV between males and females. The males had a 14% higher incidence than females.

NEUTERING/SPAYING- This was not an important factor in studying the risk of bloat.

WEIGHT- Glickman found (as well as a host of other researchers) that weight did prove to be significant. Dogs that have been categorized as chronically underweight by their owners are at a higher risk than dogs characterized as average or overweight. Glickman says this may suggest that while bloat occurs acutely in dogs that show no previous indications that they will bloat, these dogs may in fact have problems with their gastrointestinal tract long before they bloat. This may explain why they are thin. According to Glickman there are other factors that point to underlying GI tract problems. Or it may simply be because the dogs are fearful and it is hard to keep weight on fearful dogs.

DIET- Individual dog analysis also looked at different foods, the brand, the amount, the size of the kibble, fat preservatives used, canned, dry, semi-moist etc. Because this area was of such great magnitude the final analysis has not yet been completed. It is important to note that there have been previous studies where dog kibble smaller than 30mm were associated with an increased risk of developing GDV.

SPEED OF EATING- Glickman found that the faster the dog ate, the greater the risk of bloat. He believes this is a result of the excess air being gulped. One theory as to the cause of bloat has always been attributed to the speed at which a dog eats. However, the fact that many dogs that bloat do not do so immediately after eating seems to refute this widely held thought. Glickman thinks that this may be the most confusing aspect when studying GDV. Researchers have tried to determine why the stomach fills and distends so rapidly, and most bloat does not occur immediately after eating. In fact about 70% of cases of bloat occur late at night or early in the morning. Glickman says they know that what is in the stomach is air, and that air can only come from one place. It has to be ingested. So the issue now becomes what causes some dogs to ingest large amounts of air and others not to. To Glickman this suggests that there is some underlying problem that does not just occur during an acute episode, but that happens repeatedly and is exacerbated by temperament. Dogs that don't cope well gulp. As an aside, Glickman's next project is funded by the Collie Club of America and will look at abnormal esophageal motility in dogs. A European study found that the vast majority of dogs with repeated episodes of bloat have defects in their swallowing mechanism. If they can find the defect they may be able to test (Barium fluoroscopy) for it to see if their dog is at high risk for GDV.

BELCHING and FLATULENCE- Glickman asked owners to characterize their dogs in terms of flatulence and belching to see if they were also associated with greater risk of GDV. He found that in dogs that belch often had about a 60% increase in risk of GDV. In dogs that had flatulence often there was a 20% increase in risk. Dogs that had abdominal distention regularly after eating had an 80% increased risk. Glickman believes that GDV is caused by excessive air swallowing, so the belching and the flatulence may not be gas but may in fact be air. He thinks that maybe the same mechanism that leads dogs to bloat, may also lead to the belching and flatulence.

GENETICS- In the individual dog analysis one of the strongest predictors for GDV was having a first-degree relative that bloated. A first degree relative was defined as a parent, sibling, or offspring, in other words dogs that shared 50% of their gene pool. Pedigree analysis is difficult because GDV may not manifest itself until the dog is 7 or 10 years old. Though Glickman realizes pedigree analysis would be quite difficult, he thinks the undertaking would give a wealth of information to uncovering modes of inheritance that are not easily obtained when asking only about first degree relatives.

HOUSING- In previous studies a variety of stressful events such as a dog being boarded, having a pet sitter, having strange people in the house, changing residence etc. increased the rate of GDV. However, the focus of this study was on predisposing factors and not precipitating events.

WATER/EXERCISE- A common practice to prevent bloat that many people have utilized includes restricting exercise or water intake immediately before or after eating. This advice has become almost 'common sense'. However this study found that this was not associated with a reduced incidence of GDV. Another commonly held truth is called into question with this study. In fact there was even a slight increase in the rate of GDV for dogs whose owners restricted water and or exercise around meal times. This could not be conclusively stated as there were some confounding factors in the study.

ELEVATED FOOD BOWLS- On the internet, in dog food pamphlets, and in popular dog magazines, raising the food bowl has been suggested for dogs that eat quickly to help reduce the air that is gulped. However, raising the feed bowl appeared to significantly INCREASE the risk of GDV and not decrease it as was previously held. The question can then be posed, does a raised feed bowl actually increase the amount of air ingested while eating?

MOISTENING FOOD- Another common practice for people that are trying to prevent an occurrence of GDV is moistening the dogs' food. And again this study has shown just the opposite. There may be an increased risk of GDV with moistened food. This result warrants further study as well due to confounding factors.

PREVENTATIVE MEDICATION - Owners of high-risk breeds may try to medicate their dog to reduce gas formation or increase gastric motility in order to help stave of GDV. These efforts do not appear to reduce the incidence of GDV.

NUMBER OF MEALS FED- Another common recommendation for preventing GDV is feeding smaller meals more often throughout the day. Glickman found that as the number of meals increased, the risk of bloat decreased. He says if you extrapolated that you could make the conclusion that free feeding is best. But he also says they do not have the data to support the above conclusion as free feeding is just not common with owners of large and giant breed dogs. And really, who can imagine free feeding the average Labrador??? Glickman's gut instinct is the reduced incidence of bloat relates to less distension of the stomach with smaller meals.

How do you lower the risk?
Glickman has several suggestions to reduce the chances of bloat and torsion for dog owners if they feel their dog is at a high risk. His preliminary suggestions are based on what is already known:
1. Don't breed a dog if a first degree relative has suffered an episode of bloat.
2. Owners that have dogs that eat rapidly should do anything they can to slow them down (the object that has worked best was a heavy chain with big links, so the dog is forced to eat under and around it, not a large stone as is commonly recommended).
3. Owners of anxious and fearful dogs should consider behaviour modification, and drug therapy may be warranted in serious cases.
4. Feed smaller, multiple meals per day instead of one large meal.
5. Do not elevate the feed bowl.

Finally, Glickman feels the greatest value of this study is that it is prospective in nature. He means all the information about the dogs was collected before anyone knew which dogs would develop bloat and which would not. This way owners and researchers were unbiased in how the information was collected. The results of the dietary analysis component will be the subject of a future article. Special thanks go out to Dr. Glickman who was kind enough to answer all my questions and provide me with all the information to write an article that includes the latest findings in regards to GDV.

REFERENCES:

Glickman LT, Lantz GC, Schellenberg DB, et al. A prospective study of survival and recurrence following the acute gastric dilatation-volvulus syndrome in 136 dogs. Journal of the American Animal Hospital Association 1998: 34:253-259.

Glickman LT, Glickman NW, Shellenberg DB, et al. Multiple risk factors for the gastric dilatation-volvulus syndrome in dogs: a practitioner/owner case-control study. Journal of the American Animal Hospital Association 1997; 33: 197-204.

Glickman LT, Glickman NW, Perez CM et al. Analysis of the risk factors for gastric dilatation and dilatation-volvulus in dogs. Journal of the American Veterinary Medical Association 1994; 204: 1465-1471. 

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