Bloat

It's an owner's nightmare: returning home or waking up to find a beloved pet has died of gastric dilatation-volvulus, or bloat and torsion as it more commonly is known, an agonizing condition that can strike suddenly and fatally. Sadly, for many owners this nightmare has become a traumatic reality.

Dogs that succomb to the condition suffer immense pain and an obscenely distended abdomen that can grow to as large as a beach ball. They exit this world too early jarringly, and they leave their owners feeling helpless and confused. As new research emerges, however, owners may be able to fend off the fatal grasp of bloat and torsion and take steps to minimize the risks to their dogs.

Bloat is a condition in which there is a rapid accumulation of air in the stomach causing dilatation. Volvulus, or torsion, occurs when the dilated stomach twists, cutting off contact with the esophagus at one end and the small intestine at the other. This effectively isolates the stomach and traps the air.

The very enlarged, twisted stomach puts pressure on the blood vessels, often twisting them in the abdominal cavity and this impairing blood flow back to the heart. Because the heart receives an insufficient amount of blood to pump, blood flow decreases to the rest of the body. With this, there is the fairly acute onset of death of the tissues that are deprived of oxygen, including the stomach wall itself, which rapidly undergoes necrosis.

The early signs of bloat include discomfort. The dog paces or repeatedly gets up and then lies back down. There also is excessive salivation, panting and unsuccessful attempts to vomit. As the condition worsens, the abdomen distends in most - but not all - dogs and feels taut like a drum. Shock follows (i.e. pale gums, weakness, shallow pulse, cool extremities, etc.). Often, dogs then go into a coma, and death is the ultimate outcome if they are untreated.

Uncovering Etiologies:
Given that GDV is one of the leading causes of death on giant and large breeds, one would expect that much research into the cause of this pervasive killer would be under way. Yet, Larry Glickman, V.M.D., Dr.PH, a veterinary researcher at Purdue University's School of Veterinary Medicine, presently is one of the only researchers pursuing this area of study. According to him, other groups currently researching the condition typically focus on its treatment and not the cause.

Glickman presented some of the findings from his most recent "Five Year Purdue University Prospective Study of Gastric Dilatation-Volvulus" at Canine Health Conference held in St. Louis in October 1999 and sponsored by the AKC Canine Health Foundation. The purpose of the study was to isolate risk factors in order to identify the environmental situations and characteristics of dogs that make them more susceptible to the condition.

"We followed nearly 2000 dogs belonging to 11 breeds for up to five years to determine which one would develop bloat and which ones would not. Then, we related that data back to things like their breed, size, shape, personality, age, genetics, diet and how they were managed," he explains.

The study was a two part risk analysis performed at the breed individual dog levels. At the conference, Glickman reported on the first part, the breed analysis findings, which are complete, but reported only the preliminary findings of the second part, the individual dog risk factors, which still are being analyzed at the time of this writing.

Analysis At The Breed Level:
"In the first part, we tried to look for breed related risk factors," Glickman explains. "That is, characteristics that would put a breed per se at higher risk than any other breed in the study". The large breed dogs in his research were characterized as weighing between 50-99 pounds at adult weight and the giant breeds were 99 pounds and greater. (Smaller breeds were not studied because, for the most part, they are not largely affected by bloat.) The 11 breeds included in the study - chosen because they were known to be high risk - were the Akita, Bloodhound, Collie, Great Dane, Irish Setter, Irish Wolfhound, Newfoundland, Poodle (standard), Rottweiler, Saint Bernard and Weimaraner. Dogs were measured at AKC shows. On the breed level, the following characteristics were analyzed:

Breed Size:
In terms of breed risk factors, Glickman found the incidence of bloat was high and almost identical in both the giant and large breed dogs in the study. the actual incidences of bloat in both the large and giant breeds were 23 and 26 cases, respectively, per 1000 "dog years" at risk. (Each dog followed for one year represented one "dog year" at risk.) Out of the more than 1900 dogs in the study, a total 105 developed bloat. Their fatality rate was 29 percent.

The breeds at highest risk in the study were the Great Dane with a cumulative incidence rate of 15.7 percent, and the Bloodhound, with a rate of 8.7 percent. To figure lifetime rate of incidence, Glickman took observed incidence rates for the different breeds and made the assumptions that the average life span is 10 years for the large and 8 years for the giant breeds. He then calculated what the lifetime risk of bloat would be for these breeds. It was 23 and 26%. In the case of the Great Dane specifically, it was 42 percent! That means more than four out of ten Great Danes will bloat in their lifetimes. Of those that do, one third will die.

Breed Shape:
According to Glickman, it's not just a breed's size that influences the rate of bloat, however. As the breed analysis also revealed, "Breeds that have a deeper and narrower abdomen are at greater risk, with the abdomen depth/width ratio being a much stronger predictor than the chest depth/width ratio for breeds. We think that the deeper and the narrower the abdomen, the greater the room for the stomach ligaments to stretch down or lengthen as part of the aging process. The deeper abdomen provides more room for the stomach to actually descend with age. The combination of stretched ligaments and the greater room allows the stomach to "twist".

Glickman says the fact that the smaller breeds with deep, narrow abdomens have a higher incidence rate of bloat further supports the correlation of the abdomen depth/ratio and increased risk. "The only breeds of lesser size with fairly high incidence of bloat are Basset Hounds and Basset Hound shaped breeds including Dachshunds. Compared to the size of the dog, they have a very deep, narrow abdomen.

Study findings also revealed the risk of bloat between two breeds of roughly the same size. Glickman believes this is due to the difference in shape. "Compare the setters - Irish and English - to the retrievers - Golden and Labrador. Here are two breed types that are roughly the same size, yet, the setters have a much higher incidence. Setters have a very deep, narrow abdomen, while retrievers have a shallower, wider abdomen."

Temperament:
Interestingly, personality also turned out to be a major predictor of bloat at the breed level. Glickman explains, "we asked each individual in the survey to rate their dog on a scale of 1 to 10 for things like aggressive to people, aggressive to dogs, submissive to people and dogs, excitability, fearfulness, happiness, trainability, and whether the dogs are easily upset by strangers or new situations. We took the average score for each breed to get a breed average score for each of these characteristics. Then, we looked at the relationship between the scores and the risk of bloat for the breed as a whole. Two clear tre3nds emerged. First, the more fearful the breed, the higher risk of bloat, and the second, the more happy and easy going the breed, the lower the risk."

According to Glickman, it's not the amount of stress per se in a dog's life that is significant, but the way in which the animal's body reacts to it. That reaction is mediated by personality. "This is an important distinction because clearly there is nothing we can do about stress. What is significant, though, is that a happy individual, whether a person or a dog, is less influenced by stressful situations than a highly anxious, fearful one."

Differing responses to stress might influence the risk of bloat for the following reasons. "When animals are placed under stress, there are certain stress hormonal and neural responses. Some of these responses clearly affect gastric motility. A fearful dog may have a very different response physiologically to stress than a happy, easygoing dog. We think those physiological responses may contribute to the rotation of the stomach because of the motility. This is the second or third time we have demonstrated temperament-particularly easygoingness or fearfulness-is related to the risk of bloat," Glickman reports. (Note: There were significant differences among breeds in the study in terms of how the owners scored them for happiness/fearfulness. In addition, Glickman reports that even within breeds, there was variance of owner response; the scores represent averages.

The Happiness Score
Rank	Males	Females
Highest
1	Newfoundland	Rottweiler
2	Weimaraner	Collie
3	Rottweiler	Newfoundland
4	Akita	Weimaraner
5	Saint Bernard	Poodle (standard)
6	Collie	Bloodhound
7	Poodle (standard)	Irish Wolfhound
8	Great Dane	Akita
9	Irish Setter	Saint Bernard
10	Irish Wolfhound	Irish Setter
11	Bloodhound	Great Dane
Lowest

*Based on owner's reports. These scores represent averages for the purpose of the study. All dogs of any breed are individuals capable of expressing a variety of temperaments and personalities.

Aging:
Although dogs of all ages were included in the study, in general, Glickman found the incidence of bloat increased with advancing age. That means that we have to think about how bloat ties into the aging process (i.e. the stretching or lengthening of the stomach ligaments.) Breed level analysis revealed the incidence of bloat in large breed dogs started to increase dramatically at 3 years of age. In giant-breed dogs, that increase with age started much sooner - as early as 6 months. Given that blat is a disease of aging, Glickman says these findings were predictable because giant breed dogs age faster than do large breed dogs and therefore do not live as long.

Genetics:
Given the findings of this and previous studies, Glickman does not believe bloat is genetically based in the sense that one gene is responsible for causing it. "We;re dealing with a complex condition where several genes interact to produce bloat. For example, things like size, shape and personality have a genetic basis. Certain inherited characteristics predispose breeds or individuals dogs to bloat."

Individual Dog Analysis:
At the breed level, Glickman compared factors that differed among the 11 breeds in the study. "In the second part, we looked at individual dogs to see why those dogs were at increased risk compared to other dogs in the study," he says. A lot more data were collected at the individual dog level because, as mentioned earlier, there was a total of more than 1900 dogs in the study. 87% of their owners completed questionnaires, so detailed information was obtained on more than 1600 dogs.

Risk factors analyzed in the individual dog level portion of the study included characteristics such as gender, neutering/spaying, weight, belching and flatulence, speed of eating and genetics; and environmental factors such as housing, travel, vaccination, restriction of water and exercise around mealtime, use of elevated food bowls, moistening food, giving preventive medications and number of meals fed. The following outlines some of the results:

Gender:
Individual dog level analysis confirmed there is only a minimal difference in the risk of bloat between males and females. Males in the study had only a 14% higher incidence than did females.

Neutering:
Likewise, neutering did not emerge as an important factor.

Weight:
Weight, on the other hand, did prove to be significant. "We have consistently found, and have been able to replicate it in this study, that dogs characterized by their owners as chronically underweight are at higher risk than dogs characterized as average weight or even overweight," Glickman notes. "This is a very important finding now that we've seen it for the third or fourth time. It suggests that, while bloat occurs acutely in dogs that show no previous indications they will bloat, these dogs may, in fact, have problems with their gastrointestinal tract long before they bloat, which may explain why they're chronically thin. A lot of factors point to the fact that there may be related, underlying problems within the GI tract that are manifested as doing poorly in terms of weight gain. Or it may simply be because they're fearful. It's hard to put weight on fearful dogs."

Diet:
The individual dog analysis also looked at the different types of food fed to the individual dogs in terms of amount, brands, specific ingredients, fat preservatives used, fat sources used, kibble size, etc. Study participants reported more than 150 types of food being fed. Due to the magnitude of collecting information on such a large number of foods, the diet analysis is not complete at present but will be forthcoming shortly.

Speed of Eating:
Although specifics about the contents of diets still are being considered, Glickman did find in this study, as he had in previous studies, that the faster the dog ate, the greater risk of bloat. He believes the increased risk may be related to gulping air while eating, which is one theory as to bloat's cause. The fact that many dogs that bloat do not do so immediately after eating seemingly contradicts this, however.

"one of the most confusing things in studying bloat is trying to determines why the stomach fills and distends so rapidly," Glickman says. "We used to think food was the cause. Now, we know most bloat does not occur immediately after eating. In another study, we found that 70% of bloat cases occur late at night or early in the morning. We also know that what's in the stomach is air, which can only come from one place. It has to be ingested or gulped. So, the issue becomes what causes some dogs to ingest large amounts of air and others not to. This suggests there is some underlying problem that does not just occur during the acute episode, but that happens repeatedly and that may be exacerbated by temperament. That is, dogs that don't cope well gulp air."

Glickman's next study, which he already has begun and is funded by the Collie Club of America, will be a replication of a study done in Europe five years ago. The European study found that the vast majority of dogs that have repeated episodes of bloat have defects in their swallowing mechanism. That is, when they swallow food, it doesn't flow as it should from the mouth to the stomach. In order to get the food to flow, the dogs have to gulp air to force it down. So far only two dogs have been tested by Glickman. Both already had an episode of bloat and both had swallowing defects. For the first time, some clues as to what the primary physical defect may be in terms of allowing this rapid intake of air. In the future, owner's of dogs at high risk may have a test taken to determine if the dog's swallowing mechanism is defective. A bowl of barium coated dog food and following the progression of the food through the esophageal tract with a procedure called fluoroscopy.

Gas:
"We also asked owners to characterize their dogs in terms of flatulence and belching to see if they were associated with increased risk of bloat," Glickman explains. "In fact, both were. In dogs that belch often there was a bout a 60% increased risk of bloat. In dogs that had flatulence often vs. rarely, there was about a 20 percent increased risk. Dogs that had abdominal distention after eating regularly had about an 80% increased risk.

Genetics:
In the individual dog analysis, having a first degree relative that bloated turned out to be one of the strongest predictors. In fact, dogs with such relatives had a 3 and 4 fold increased risk of developing bloat. A first degree relative was defined as ether a parent, sibling, or offspring, in other words, dogs that shared 50% of the gene pool.

Glickman believe s that grandparents that bloated also indicate risk. Pedigree analysis is difficult, however, because bloat is a disease of aging that may not manifest until a dog is 7 or 8 years old. Because of this, dogs have to live almost their whole lives before bloat in the pedigree could be known. Bu that time, people often have lost track not only of grandparents, but parents and siblings as well.

Management:
In terms of environmental risk factors, which included management, the individual dogs analysis looked at things such as how the animals were housed, if they traveled, the frequency of vaccination, etc. No one of these appeared to be associated with an altered risk of bloat. However,r the study did reveal an increased risk of bloat associated with things such as restricting water before and after eating, giving preventative medications, moistening the food and raising the bowl's height. These findings were of great interest to Glickman because these measures commonly were thought to be preventive.

To further clarify these seemingly contradictory findings, Glickman compared the rate of use of these preventative measures in dogs that had a first degree relative that bloated and in those that did not. He found that these practices more commonly were used by owners with dogs at high risk. Glickman then further analyzed the data to determine whether these practices are associated with bloat simply because the owners accurately had identified the high risk dogs ahead of time, or it they actually were harmful or had no effect.

Prior to this last step in his analysis, his gut feeling was that all these practices probably would prove to have no effect. Indeed, his "final analysis shows that this is correct-except for raising the food bowl, which does appear to increase the risk of bloat. The higher the bowl, the higher the risk." Glickman says the elevation may be causing an increased incidence of aerophagia (excessive swallowing of air), which could account for the higher risk.

Meal Frequency:
Another commonly recommended measure for preventing bloat is feeding smaller, multiple meals. This procedure's effectiveness was born out by the individual analysis part of the study. "In previous studies, we showed that as the number of meals increased per day, the risk of bloat decreases. We found the same thing in this study. If you take that to the fullest, the free feeding should be best. We don't have the data to support that conclusion, however, because we don't have enough data on free feeding in any of these studies to look at it by itself, since free feeding is not commonly done with large/giant breeds." He believes that the link between feeding multiple meals and a lower incidence of bloat may be related to less distension of the stomach with smaller meals.

Lowering the Risks:
After reviewing the results of Glickman's study, if you believe your dog may be in the high risk category, there are steps you can take to actively reduce the chances of bloat/torsion. Glickman makes the following preliminary recommendations based on what already is known:

1) Don't breed a dog if a first degree relative had suffered an episode of bloat.
2) Consider a prophylactic gastroplexy for dogs that fit the high risk profile. (Note: It should only be performed on dogs already neutered or will be neutered at the time of gastroplexy. Breeders who prevent high risk dogs from bloating by opting for this surgery, but then continue to breed the dogs, mask the problem and destroy selection criteria in a breeding context.
3) Owners who have dogs that eat rapidly should do anything that they can to slow the speed of eating. The most common and effective strategy was to place a large object that the dog had to eat around in the food bowl. For example: A heavy chain. A heavy link chain forces the dog to eat under and around it unlike a large rock that can be pushed away.
4) Owners of anxious or fearful dogs should consider behavior modification and consult a behaviorist or vet. In some instances drug therapy is warranted.
5) Feed smaller, multiple meals instead of one large meal per day.
6) Do NOT elevate food bowl.

Glickman believes the greatest value of this study is that it is prospective. That means he collected all the information on the animals before the owners ever knew which ones would develop bloat and which would not. Thus, he and the owners were totally unbiased in the way in which the information was collected. This is very different from all the other studies that have been done up until now. They took dogs that had already bloated and then went back and asked owners how they managed the dogs. Of course, owners of dogs that bloated remembered things much differently than owners of dogs that did not.

The initial study findings will be published in the Journal of American Veterinary Medicine.