Gastric Dilatation-volvulus

5. Gastric Dilatation-volvulus

Gastric dilatation-volvulus (GDV) is a sudden, dramatic and often fatal disorder. Overall mortality of up to 30% has been reported in some studies. Older dogs are most commonly affected, although GDV can potentially affect dogs of any age. The most important risk factor is body conformation and, in this regard, a narrow deep chest is associated with increased risk (Glickman et al., 1994). Although many studies have incriminated diet (e.g., ingestion of dry, cereal based foodstuffs), no clear association has been proven. Other potential incriminating factors include single large meals, overeating, small kibble size, elevated feeding bowls, post-prandial exercise, anesthesia, aerophagia, and previous gastric "injury".

Feeding from a height is a risk factor for gastric dilatation and volvulus in high-risk dogs (Glickman et al., 2000). (© Psaila).

Gastric dilatation is the rapid distension of the stomach with food, fluid or air, and can rapidly progress to volvulus (e.g., rotation of the stomach along its long-axis). Rapid gastric dilation affects lower esophageal function, and impairs gastric motility and emptying. The gastric mucosa can later undergo ischaemic necrosis. Accumulation of gastric secretions and occlusion of venous return from the caudal body can lead to hypovolemic and cardiogenic shock. Splenic torsion with infarction is another common sequel.

Large kibbles (30 mm x 30 mm x 20 mm) help prevent aerophagia. Aerophagia increases the risk of gastric dilatation and volvulus (Theyse et al., 2000).

Most animals present with a history of progressive (often rapid) abdominal distension, non-productive retching/vomiting, and hypersalivation. On physical examination gastric tympany is usually obvious, but absence of clear symptoms does not exclude the possibility of a dilatation/volvulus of the stomach. Treatment involves emergency stabilization with aggressive intravenous fluid therapy, and gastric decompression (ideally by gastric intubation). If appropriate, corrective surgery (e.g., gastropexy) should be performed once the animal is stable (ideally within the first 3 - 6 hours). Other adjunctive treatments (many post-operatively) include antibacterials, H2antagonists, sucralfate, intravenous fluid therapy, gastric intubation, lavage and decompression, and anti-arrhythmics (if appropriate).

Gastric dilatation and volvulus particularly affects large breeds with a deep chest (St Bernards, Great Danes, Weimaraners, Gordon Setters, Irish Setters and Standard Poodles). (© Psaila).

Dietary Management of GDV

The dietary risk factors for the development of gastric dilatation and volvulus are not clear. In addition, there are no studies available on the dietary effects that would help to prevent gastric dilatation in predisposed dogs. Data available from clinical cases demonstrate increased microbial fermentation in the stomach of affected dogs with the accumulation of bacterial fermentation products (gas, lactic acid, volatile fatty acids) (Van Kruiningen et al., 1974,Rogolsky et al., 1978). Gas composition in clinical patients was similar to atmospheric air, indicating that aerophagia could be a significant factor in the pathogenesis of the disease (Caywood et al., 1977). The stomach content of dogs is physiologically colonized with a large number and variety of microorganisms (Benno et al., 1992a,Benno et al., 1992b). Imbalance in the bacterial flora e.g., increased numbers of clostridia have been considered as one potential factor in the etiology of the disease. However, in one study comparing diseased and healthy dogs the authors were unable to demonstrate differences in the clostridial colonization of the stomach of these dogs (Warner et al., 1978).

Although the pathogenesis is not yet unders-tood, it is justified to recommend certain dietary measures.

• Dogs at risk should be fed three small meals and not one single meal a day (Raghavan et al., 2004).
• Owners should be advised not to use elevated feeding bowels as this appears to be a risk factor for GDV.
• Food and feeding hygiene should not be ignored. Food bowls should be regularly cleaned and food should not be stored for excessive periods, especially when it is mixed with water.
• Owners of affected dogs should be advised to feed the dogs as regularly as possible because this consistency conditions the secretory and digestive functions of the gastrointestinal tract.
• Stress should be avoided after food intake, because it can have negative effects on gastric secretion (avoid exercise post-feeding).
• Diets for dogs at risk of developing gastric dilatation and volvulus should not contain elevated mineral levels. Minerals have a high buffering capacity and may maintain the gastric pH at higher levels which allows the microorganisms to be more active compared to an acidic environment.
• Fat and especially unsaturated fatty acids have a capacity to reduce microbial fermentation. Although not experimentally proven it seems to be advisable to feed patients at risk of GDV with diets containing higher fat levels (Meyer & Zentek, 2001).