Gastric Dilatation Volvulus (Bloat) update

Gary W. Ellison, DVM, MS, DACVS
University of Florida
Gastric dilatation Volvulus complex also know as bloat is a medical and surgical emergency which is know to primarily affect large and giant breeds of dogs. The disease has also been reported in smaller breeds such as the Pekingese and Dachshund. Mortality has been estimated as high as 30 percent. There are no reliable estimates of how many dogs develop bloat in the United States each year, but in certain breeds such as Irish Setters and Great Danes owners reported an incidence of seven and ten percent respectively. It does appear that purebred dogs are more likely to develop bloat than are mixed breed dogs.

Results of Retrospective Studies
Incidence
Several recent reviews by Dr. Larry Glickman at Purdue University utilizing information from the veterinary medical database (VMDB) have discovered some interesting findings:
1) Amongst veterinary institutions the frequency of bloat amongst all dogs ranged from 2.9-6.8 per 1000 dogs
2) Approximately 29 percent of the dogs with gastric dilatation and 33 percent of those with dilatation and volvulus died.
3) Aging of the dog increased risk. Dogs greater than seven years of age are more than twice as likely to have bloat as dogs 2-4 years of age.
4) Purebreds were three times as likely to have bloat as mixed breed dogs.
5) Males are twice as likely to bloat as females yet spaying or neutering has no effect on the risk of bloat.

Studies of Risk Factors
Several risk factors have been identified which may contribute to the establishment of bloat in purebred dogs.

Breed Bloat has been long reported to be more common in large and giant breeds of dogs yet until recently the prevalence of bloat was not compared to the dog population at large. When this data was analyzed statistically, it was found that the Great Dane, St. Bernard, Weimaraner, Irish Setter and Gordon Setter were breeds at greatest risk. An accompanying chart outlines the remainder of the breeds (Table 1).

Chest Conformation Although it is established that large and giant breeds are the breeds at greatest risk it has been shown there are profound differences in the risk of bloat within certain breeds. This possibility seems related to conformation of the animal’s chest. For instance, breeds such as Irish Setters which are at high risk may weigh approximately the same as some of the Retriever breeds yet the Retrievers are at much lower risk than Irish Setters for developing bloat. When looking at this more scientifically it was found that the depth and width of the chest may be the key in predicting which animals within a certain breed may develop bloat. It appears that the chest depth/width ration is highly correlated with risk of bloat, ie. Those animals with deep, narrow chests within a certain breed are much more likely to develop bloat than those dogs with deep wide chests. In using external measurements of chest conformation it was found that within the Great Dane breed the depth/width ration may indeed be useful in identifying animals prone to bloat. Also, Great Danes with moderate and high abdominal height to width ratios were approximately 8 times as likely to develop bloat as those with low abdominal height to width rations. In Irish Setters the chest height to width ration also correlated with those dogs having a higher depth to width ration being much more likely to develop bloat than those animals with a lower depth to width ration. This information is obviously very significant in terms of selective breeding for the reduction of bloat in these breeds.

Diet Exact determinations of types of diet on risk for developing bloat still cannot be made. Although cereal-based diets have incriminated, it is difficult to compare groups since almost all large and giant breeds are fed cereal-based diets. Therefore, further controlled studies will be necessary to determine if cereal-based diets are in fact a risk factor. However, several interesting findings have come to surface with regard to the diet and nutritional management of breeds predisposed to bloat. For instance, it has been shown that dogs who eat one meal a day are almost twice as likely to develop bloat as those fed twice a day. The rate of eating is also very important. Those dogs characterized as slow eaters have the lowest incidence of bloat whereas those dogs characterized as moderately fast eaters have about 2 times the chance of developing bloat and those characterized as fast eaters have almost five times the chance of developing bloat as those being characterized as slow eaters.
Body weight may also be of some significance. Being overweight actually reduced the incidence of bloat compared to dogs that were optimum weight. However, those animals characterized as significantly underweight were about three times as likely to develop bloat as those animals characterized as optimum weight.

Gender It has been shown that males are approximately twice as likely to develop bloat as females. Neutering does not seem to have an effect on the incidence however.

Personality and Environment There does seem to be a direct correlation of the animal’s temperament relating to its tendency to develop bloat. Those animals being characterized as unhappy or fearful were about 2 times as likely to develop bloat as those animals characterized as happy. In addition, the environment may play a role. Stress appears to also significantly increase the chance of the animal developing bloat. Therefore, animals who may undergo significant stress traveling to show, etc. are tow to three times as likely to bloat than those animals who are not significantly affected by the transport. Also activity level may be important with those animals characterized as hyperactive and those animals being categorized as less active were twice as likely to develop bloat than those animals characterized as having a normal activity level.

Summary and Conclusions
With regard to known epidemiologic factors affecting bloat some of the following recommendations can be made. It appears there is a correlation with chest and abdominal height/width ratio with those animals having tall thin chests and abdomens more likely to develop bloat than those with lower, wider chests and abdomens, there selective breeding may possible be recommended to diminish the incidence due to conformation.

With regard to diet and nutrition changes in feeding relating to twice a day feeding versus once a day feeding may be recommended. Also, changing the time of the meal is significant with those animals having constant changes in meal time being approximately 2 times as likely to develop bloat as those being fed at regular intervals. In addition, those animals undergoing a sudden increase in food intake are almost three times as likely to develop bloat as those animals kept on a regular food intake. Therefore, recommendations may be made to keep consistency and times of feeding regulated and to feed the moderate amount of food without sudden increases in the amount fed.

It also appears that reducing the amount of stress on the animal will decrease the chances of bloating. Although no specific recommendations can be made about tranquilization knowing the temperament of your dog may help you in minimizing the amount of stress encountered during travel to and from shows. It also appears that keeping physical activity to a moderate amount that is what the animal is used to, will be more helpful in reducing the chances of bloat than allowing extra activity than normally expected.

Etiology
The exact etiology of GDV is unknown, but it is most likely a multifactorial disease. Ingestion of cereal based diets and water followed by exercise is reported in some but not the majority of cases. Stretching of the hepatogastric or hepatoduodenal ligaments from chronic overeating may allow transposition of the stomach. Gastric outlet obstruction by foreign bodies has been observed in some cases but delayed gastric emptying caused by pyloric hypertrophy is not conclusively proven as a cause of GDV. Splenic torsion or displacement occurs secondarily to GDV rather than initiating it, as was once believed. Gas production secondary to bacterial fermentation by clostridial organisms is a postmortem finding and is not a source of gas in live animals. Aerophagia is a likely cause since gas composition of the gastric lumen resembles atmospheric air and the onset of GDV often follows vigorous exercise, excitement and barking.
Recently there is evidence that gastric motility disorders may induce or follow GDV.

Clinical Signs
Dogs usually demonstrate hypersalivation, retching or unproductive vomiting on presentation. Cranial abdominal distention is apparent and gastric tympany is usually present on blunt percussion of the right anterior quadrant. Hyperpnea or dyspnea accompanied by open mouth breathing indicates hypoxia due to reduced diaphragmatic excursions. Shock is evidenced by pale or injected mucous membranes, prolonged capillary perfusion, tachycardia and weak rapid femoral pulse.

Mechanisms of Rotation
A lack of coordinated gastric contractions due to gastric myoelectric dysrhythmias may slow gastric emptying and contribute to the development of gastric dilatation volvulus (GDV). Food and fluid distension from overeating or gaseous distension from aerophagia causes intra-abdominal angulation of the gastroesophageal junction that prevents belching or vomiting.
Gastric dilatation results. Volvulus occurs when the dilated gastric fundus becomes displaced from a left dorsal to a right ventral position. The pylorus concurrently shifts from its right ventral position to a left, caudal and dorsal position. When viewed from the rear a clockwise rotation occurs in the majority of the animals. The spleen follows the greater curvature to the right. The gastrosplenic ligament and short gastric arteries are often torn during the volvulus.

Initial Management of GDV
Initial patient management involves shock therapy, and gastric decompression followed by management of cardiac arrhythmias. Shock therapy involves fluid loading with 90 ml/kg of lactated Ringers solution of the first hour. The use of hypertonic saline may also be beneficial,
as it has been shown to be beneficial in increasing gastric arterial perfusion. Treatment for acid- base status is controversial with one study indicating normal pH and another indicating the presence of metabolic acidosis in cases of GDV. However, with mild metabolic acidosis Na bicarbonate infusion is not necessary as long as adequate volume replacement with lactated Ringers solution is achieved. Hypokalemia is a common finding associated with GDV and potassium replacement is sometimes warranted. Corticosteroids are administered after initial treatment with intravenous fluids. They cause vasodilation and improved tissue perfusion if fluid volume is adequate. Cardiac dysrhythmias are commonly seen and require careful pre- and postoperative management. Paroxysmal vent4ricular tachycardia, and premature ventricular contractions are most commonly seen. Gastric decompression is accomplished using a pre-measured, well lubricated PVC plastic foal nasogastric tube. Ability to pass the tube into the stomach does not mean that gastric volvulus is not present. If intubation is not possible in the prone position it is attempted in a sitting upright position. Sometimes trocharization is necessary to reduce distension and facilitate tube passage.
The character of the fluid is sometimes important in predicting the status of the gastric lining. Black fetid smelling fluid with flecks of devitalized mucosa indicates that mucosal ischemia is present and often predicts the presence of gastric wall necrosis. After decompression, the stomach is lavaged with 4-5 liters of water using gravity flow, dose syringe or stomach pump.

Radiography
Radiography is always postponed until after patient stabilization. With gastric dilatation the stomach appears as a grossly distended gas and fluid filled structure that occupies the cranial abdomen displacing all remaining viscera posteriorly. The spleen is usually not visible in its normal left ventral location and is often located in a right dorsal position. Gastric volvulus is suspected when the pylorus is located dorsal, cranial and to the left of the midline. After decompression it may take a classic upside down appearance. Left and right lateral views are recommended. On the right lateral view gas can be seen in the pylorus whereas on the left lateral view gas may be seen in the fundus. If stomach position is questionable barium sulfate is administered to identify the pylorus.

Surgical Management
Definitive management of GDV involves 1) repositioning of the stomach with resection of any devitalized gastric wall and 2) a prophylactic gastropexy technique to prevent recurrence. UP to 80 percent recurrence of GDV is reported with gastric decompression or repositioning alone.
We now advocate laparotomy as soon as the patient is a reasonable anesthetic risk. This allows early derotation that increases circulation and allows assessment of gastric wall viability. Areas of necrosis are detected early and resected if possible. With 270o to360o clockwise gastric volvulus the dilated stomach is covered on its ventral aspect by omentum. Reduction is accompanied by passing the had down the left abdominal wall, grasping the pylorus in its left dorsal position and rotating it in a caudal and counter-clockwise manner to its normal right sided location.

Gastrectomy Techniques
Standard methods for gastrectomy involve ligation of branches of the left gastroepileploic arteries and veins allowing areas along the greater curvature of the stomach to be resected. The stomach is resected back to areas of healthy bleeding. Spillage is likely and prevented through the use of Babcock forceps or stay sutures. After resection is complete the stomach is closed in two layers. The mucosa and submucosa are closed with a continuous inverted Cushing pattern of 2-0 or 3-0 PDS or Maxon. The serosa and muscularis are then closed with a similar pattern.
Recently we have relied heavily on the autostapling equipment for rapid gastrectomy procedures with minimum risk of spillage. The TA90 autostapler is used with the green (4.8 mm) or blue (3.5mm) cartridge. Often several end-to-end staple lines have to be placed since each staple line is only 9 cm in length. The surgeon needs to overlap the staple lines by a few mm to prevent leakage between the staples.

Rationale for Gastropexy
By definition gastropexy describes the fixation of the stomach to nearby structures or body wall as a means of preventing recurrence of GDV. Although gastropexy procedures reportedly diminish the recurrency rate of DGV, their reliability in producing permanent adhesions between the stomach and abdominal wall is not well documented.
Most North American surgeons use an antral gastropexy procedure to fix the gastric antrum to the right abdominal wall. The three major categories of permanent antral gastropexies used in North America are the tube gastrostomy described by Parks (1976); the incisional gastropexy described by MacCoy (1982); and the circumcostal gastropexy described by Fallah (1982). In addition, two modifications of muscle flap techniques, one using a muscular flap from the abdominal wall (Shulman, 1986) and another using a belt-loop from the gastric muscularis (Whitney, 1989), have recently been described.

Clinical Results
Potential advantages of the tube gastropexy are that 1) the surgery is rapid and easy, 2) the tube not only creates a permanent adhesion of the gastric antrum to the abdominal wall preventing recurrence of volvulus but also 3) allows for continued gastric decompression in the early postoperative period and 4) slurried food or medications can be offered through the tube. The main disadvantages of the technique are 1) the nursing care and long hospital period required for tube management and 2) the potential for fatal peritonitis secondary to leakage around the tube or early removal by the dog.
Clinical studies of the tube gastrostomy have yielded encouraging results. Flanders (1984) reported recurrence of volvulus in only one of 29 dogs treated with tube gastrostomy for a follow-up time ranging from 14 to 40 months. However there was a mortality rate of 31 percent during the first week after surgery. Johnson (1984) reported on 76 cases where this technique was used with only a five percent recurrence rate. Older studies describe a recurrence rate as high as 29 percent (Walshaw, 2976) as well as a 17 percent complication rate (Fox 1985) including premature dislodging of a tube, peritonitis, subcutaneous cellulites and persistent
stoma drainage.
Advantages of the incisional gastropexy are that 1) the procedure is rapidly done, 2) the stomach lumen is not entered and 3) fibrous connective tissue enters the abdominal rectus muscle and stomach wall to form a strong mature adhesion. The potential disadvantage is that the gaseous decompression is not provided in the postoperative period. The incisional gastropexy is popular among many North American surgeons but unfortunately no good retrospective studies are available to determine its clinical efficacy.
The circumcostal technique has become popular for use in academic medicine because it probably forms a stronger adhesion. It is reported to be more difficult to perform than the other techniques but the author disagrees with this statement. Potential advantages include a 1) viable muscle flap adhesion as well as 2) a more proper anatomic placement of the stomach. Potential disadvantages include a prolonged surgical time, potential for rib fracture and potential for pneumothorax because of the close proximity to the diaphragm. Lieb (1984) reported on 39 dogs with circumcostal gastropexies to have a slightly lower recurrent rate (2.6 percent at 13.7 months) than dogs with tube gastrostomy.
Belt loop gastropexy offers similar advantages to the circumcostal and incisional gastropexies in that the gastric lumen is not entered and the risk of peritonitis is minimal. The technique is easily performed by an unassisted surgeon. Although the belt loop gastropexy has not been evaluated biomechanically one would suspect that breaking strengths would be superior to incisional or tube gastrostomy techniques but not quite as secure as circumcostal techniques since the base of the flap is narrower than the latter technique.

Postoperative Management

Diligent postoperative care is mandatory for successful outcome of the gastric dilatation volvulus patient. Most dogs that die in the postoperative period will do so within the first 3-4 days after surgery. After major gastric resection the animal is kept NPO for a period of 24-48 hours.
Maintenance fluid, electrolyte and acid base status is critical during this period. Maintenance fluid should be given at a rate of 40-60 ml/kg per day. Although many dogs maintain normal serum potassium levels following gastric dilatation volvulus a total body potassium deficit may exist because of the NPO status, vomiting, oral gastric innervation and removal of gastric secretions. Therefore, supplementation of 20 mEq of potassium chloride is usually added to each liter of fluids to help maintain a total body potassium. Hypokalemia can also contribute to the development of cardiac arrhythmias, and gastrointestinal ilius.

The Role of Reperfusion in GDV

Mortality associated with gastric dilatation volvulus is most often due to gastrointestinal ischemia secondary to the large twisted stomach. It has been estimated that mortality can increase to 60 percent in the presence of gastric necrosis. Tissue ischemia to the gastric wall occurs due to reductions in arterial perfusion and venous stasis within the stomach wall. When the stomach is decompressed via the stomach tube and derotated via surgery there is rapid reperfusion of this ischemic tissue. Paradoxically, tissue ischemia followed by reperfusion with oxygenated blood may further increase tissue damage due to a phenomenon known as reperfusion injury.
Reperfusion injury is thought to be mediated through the activity of oxygen-derived free radicals that is based on an iron dependent mechanism. These free radicals result in cellular lipid peroxidation and cell death. Since GDV is associated with high mortality and since most deaths occur within 96 hours of surgical intervention it is plausible that treatment directed toward preventing or moderating reperfusion injury may improve survival following the correction of GDV. Studies in experimental dogs with GDV have shown that xanthene oxidase inhibitors such as allopurinol and iron chelators such as deferoxamine have been helpful in reducing the amount of free radical production consequently minimizing cellular damage due to reperfusion injury and potentially decreasing mortality associated with GDV. Although experimental results are preliminary, it is likely that within five years some of these now experimental drugs will be utilized in emergency centers for the clinical management of GDV.

Bloat Risk Ranking for 24 Purebreeds, Compared with Risk for All Dogs Combined *

Breed Affected Not Affected Risk Rank


Great Daneâ€

St. Bernardâ€

Weimaranerâ€

Irish Setterâ€

Gordon Setterâ€

Standard Poodleâ€

Basset Houndâ€

Doberman Pinscherâ€

Old English Sheepdog

German Shorthaired Pointer

Newfoundland

Airedale Terrier

German Shepherd Dogâ€

Alaskan Malamute

Chesapeake Bay Retriever

Boxer

Collie

Labrador Retriever

English Springer Spaniel

Samoyed

Dachshund

Golden Retriever‡

American Cocker Spaniel

Miniature Poodle‡


299

81

49

180

24

47

39

139

27

25

13

12

202

23

10

28

39

72

18

13

26

37

14

10


37

19

13

65

10

33

34

130

29

28

15

15

246

29

14

39

71

182

45

42

81

158

115

159


1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

*Rank based on unadjusted odds ration (an estimate of relative risk) in purebreeds for which
there were > ten cases and > eight controls. All dogs combined (pure and mixed breeds)
included 1934 cases and 3868 controls.
†Risk significantly higher than for all dogs combined.
‡Risk significantly lower than for all dogs combined.
From Glickman LT2. Epidemiologic Studies on Bloat in Dogs. Purina Veterinary Previews,1992; 2: 10-15.
References
1) Glickman LT, Glickman NW, Shellenburg DB, et al.: Multiple risk factors for the gastric dilation volvulus syndrome in dogs: A practitioner/owner case control study. J Am Anim Hosp Assoc 33: 197-204, 1997.
2) Glickman LT, Glickman NW, Shellenburg DB, et al.: Epidemiologic studies of bloat in dogs. Purina Veterinary Previews 2: 10-15, 1997.
3) Badylak SF, Lantz GC, Jeffires M: Prevention of reperfusion injury in surgically induced gastric dilatation volvulus in dogs. Am J Vet Res 51:294-299, 1990.
4) Ellison GW: Gastric dilatation volvulus: Surgical prevention. Vet Clinics N Am 27: 513-521, 1993.
5) Glickman LT. Epidemiology of gastric dilatation-volvulus in dogs. Waltham Focus 7:9-11, 1997.

Dog Owners and Breeders Symposium
July 28, 2001
University of Florida
College of Veterinary Medicine