GASTRIC DILATION VOLVULUS (GDV) or BLOAT
A Brief History
Gastric dilation volvulus (GDV), commonly known as bloat, is a life threatening condition which occurs most frequently in large, deep chested dogs. Although the incidence is relatively low it has a mortality rate of up to 60% and therefore remains a cause for concern to veterinary surgeons, breeders and owners.
In the initial stages of the syndrome dilation begins with the accumulation of gas in the stomach primarily through aerophagia and possibly fermentation. Fluid secretions also accumulate and the gastric content is prevented from leaving the stomach by failure of normal outflow mechanisms. The stomach then begins to rotate about it's oesophageal attachment in a clock or anti-clockwise direction. The region of the stomach called the pyloric antrum moves across the abdominal floor and comes to lie alongside the oesophagus on the left abdominal wall. The fundal region of the stomach moves to the right around the oesophageal axis and then ventrally. The spleen moves dorsally and to the right making contact with the liver or diaphragm. Venous return to the heart is then dramatically reduced as the result of torsion of the caudal vena cava and portal vein. Despite some progress on the treatment of GDV, its cause remains unknown.
In 1984 Leib reported that gastrin, a gastric regulatory hormone, levels are significantly higher in dogs suffering from GDV during both the syndrome and the postoperative period. They proposed that the trophic effect of gastrin on the gastric mucosa could play a role in the development of GDV by delaying gastric emptying secondary to pyloric hypertrophy amd obstruction. They also believed that gastrin concentrations could directly delay gastric emptying and increase gastroesophageal sphincter pressure resulting in oesophageal spasm, aerophagia and decrease the possibility of vomiting thus leading to the onset of GDV. However, this hypothesis has been questioned because gastrin is eliminated through the kidneys, and, since renal blood flow is significantly reduced during GDV, this possibly accounts for the elevation. In 1989 a study by Hall found that gastroesophageal sphincter pressure and plasma gastrin concentrations in postoperative dogs treated for GDV were not significantly different from values of normal dogs. They also reported that the increase in gastroesophageal sphincter pressure in response to food-induced gastrin release was similar for dogs that had recovered from GDV and clinically normal dogs. The consensus of recent studies thus does not support a significant difference in regulatory hormone levels and gastroesophageal sphincter pressure in control dogs and those with GDV.
Diet and feeding patterns have also often been proposed as possible causes of GDV. Researchers have proposed that a once daily feeding of dry dog food could predispose a dog to the development of GDV by causing a heavy, chronically distended stomach that could easily undergo torsion. However, the same study found no significant difference in gastric motility and emptying patterns among dogs fed various diets. It has also been suggested that dry cereal or soy based foods could be a causative factor. It has been hypothesized that this food may take longer to empty due to it's physiochemical composition and perhaps thereby be predisposed to fermentation, resulting in a build up of gas that could lead to GDV. This is unlikely to be the cause since GDV develops in dogs subjected to a variety of feeding regimens, diets and has even been documented in hospitalised dogs that have fasted for over 24 hours. Research at the University of Florida and Colorado State University found no effect of diet on gastric function or the onset of GDV. No overall consensus has been established, but most suggest that small frequent meals are advisable for predisposed breeds.
A recent study, however, has shown a predilection of GDV for large and giant breeds of dogs. It was found that if small dogs (< 10 kg) were assigned a risk factor of 1, then medium dogs (11-39 kg) have a risk factor of 17, while large breeds (40-49 kg) had a risk factor of 23.5 and giant breeds (> 50 kg) 133.2. The study also found a predilection for pure bred dogs which have a 2.5 times higher risk of developing GDV than mongrels of similar size. There is also some evidence to support a familial susceptibility. Among colonies of dogs kept under identical conditions only certain lines had a tendency to develop GDV. The reason why large and giant breeds are predisposed to GDV is unclear. Perhaps gastric anatomy or function is different. If this is the case however, it is still not clear why pure bred dogs are at a much higher risk.
Recommendations to help avoid GDV
1) Feed your dog two to three times daily, rather than once a day, and at times when someone can observe them after they have eaten.
2) Avoid rigorous exercise, excitement and stress one hour before and two hours after feeding. Walking is okay because it helps to stimulate normal gastrointestinal function.
3) Make diet changes gradually over a three to five day period. It has also been recommended to elevate both water and food dishes.
4) Ensure that water is always available but limit the amount immediately after feeding.
5) Watch for any actions or behaviour that may signal abdominal discomfort:
getting up and lying down
looking at abdomen
unsuccessful attempts to vomit
6) Establish a good relationship with your veterinarian.
GVD Phases, Symptoms and Recommended Actions
Phase 1 Symptoms:
Pacing, restlessness, panting and salivating
Unproductive attempts to vomit (every 10-20 minutes)
Abdomen exhibits fullness and beginning to enlarge
Phase 1 Actions:
Call vet to advise your suspicions.
Phase 2 Symptoms:
Very restless, whining, panting continuously, heavy salivating
Unproductive attempts to vomit (every 2-3 minutes)
Dark red gums
Elevated heart rate (80-100 bpm)
Abdomen is enlarged and tight. Emits a hollow sound when percussed.
Phase 2 Actions:
Call vet, your dog is likely to need urgent attention
Phase 3 Symptoms:
Gums are white or blue
Dog unable to stand or has spread-legged, shaky stance
Abdomen is very enlarged
Extremely elevated heart rate (+100 bpm) and weak pulse
Phase 3 Actions:
These symptoms indicate that death is likely to be imminent