Gastric Dilation and Rupture - Horse

The most common cause of gastric dilatation in horses is excessive gas or intestinal obstruction. Gastric dilatation may be associated with overeating fermentable feedstuffs such as grains, lush grass, and beet pulp. Presumably the large increase in production of volatile fatty acids inhibits gastric emptying. If untreated, gastric dilatation associated with overeating can rapidly lead to gastric rupture. If intestinal obstruction is the cause, the obstruction most often involves the small intestine. The fluid from the obstructed small intestine accumulates in the lumen of the stomach, causing dilatation of the stomach and retrieval of gastric reflux on passage of the nasogastric tube. Gastric dilatation also may develop in some horses with certain colonic displacements, most notably right dorsal displacement of the colon around the cecum (see Cecum and Large Intestine). It is presumed that the displaced colon obstructs duodenal outflow. Gastric dilatation with fluid also is a characteristic of proximal enteritis-jejunitis. Rupture of the stomach is a fatal complication of gastric dilatation. The stomach generally tears along its greater curvature. About two-thirds of all gastric ruptures occur secondary to mechanical obstruction, ileus, and trauma; the remaining cases are due to overload or to idiopathic causes. Clinical signs associated with gastric dilatation include severe abdominal pain, tachycardia, and retching. The mucous membranes may be pale. Classically, these acute signs are replaced by relief, depression, and toxemia after the stomach has ruptured. The prognosis for survival may be excellent in most cases of gastric dilatation, but gastric rupture is fatal. (Merck)

Dilation is primary, secondary or idiopathic. Causes of primary: gastric impaction, grain engorgement, excessive water intake after exercise, aerophagia and parasitism(141, 146). Secondary more common and can result from primary intestinal ileus or small or large intestinal obstruction. Time to development of gastric reflux is proportional to the distance to the intestinal segment involved, with duodenal obstruction resulting in reflux within 4 hours(147).

Clinical signs of gastric dilation

• Acute colic
• Ingesta appears at nares in severe cases

When rupture occurs, horses may exibit signs of relief. Tachypnea, tachycardia, sweating and muscle fasciculations are consistent with peritonitis and shock.

Lab abnormalities(141)

• Haemoconcentration
• Hypokalaemia
• Hypochloraemia

Aetiology of gastric rupture

• Secondary to small intestinal obstruction
• Primary gastric dilation
• Idiopathic gastric dilation

Risk factors for gastric rupture(146, 148)

• Feeding grass hay
• Not feeding grain
• Gelding
• Non-automatic water source

Nasogastric intubation does not preclude the possibility of gastric rupture, and the amount of reflux obtained before rupture is highly variable(146) Usually occurs along the greater curvature. In horse with rupture due to gastric dilation, the seromuscualris likely wekaens and tears before the mucosa(146,148). In rupture secondary to gastric ulceration, there is usally full-thicknees tearing of equal size in all layers.

Treatment

Surgical repair has been reported for partial thickness tears(149) and one case of a full thickness repair(150).

Prognosis

Gastric rupture is usually fatal because of widespread contamination of the peritoneal cavity, septic peritonitis, and septic shock. Food Engorgement: also carries the risk of secondary laminitis.