Changes

==Aetiology==

==Aetiology==

*'''Primary causes:''' [[Gastric Impaction - Horse|gastric impaction]], food engorgement, excessive water intake after exercise, aerophagia and parasitism(141,146).  Excessive consumption of fermentable feeds (grains, lush grass, and beet pulp) causes a large increase in the production of volatile fatty acids which is thought to delay gastric emptying.(Merck)

*'''Primary causes:''' [[Gastric Impaction - Horse|gastric impaction]], food engorgement, excessive water intake after exercise, aerophagia and parasitism(141,146).  Excessive consumption of fermentable feeds (grains, lush grass, and beet pulp) causes a large increase in the production of volatile fatty acids which is thought to delay gastric emptying.<ref name="Merck">Merck & Co (2008) '''The Merck Veterinary Manual (Eighth Edition)''', ''Merial''.</ref>

*'''Secondary causes:''' primary intestinal ileus or small or large intestinal obstruction.  Dilation resulting from small intestinal obstruction is the most common cause.  Fluid from the obstructed small intestine accumulates in the stomach, causing [[Colic Diagnosis - Naso-gastric Intubation|naso-gastric reflux]].  Gastric dilation may also occur with certain colonic displacements, especially '''right dorsal displacement of the colon''' around the caecum.  It is hypothesised that the displaced colon obstructs duodenal outflow.  Gastric fluid accumulation is also characteristic of '''proximal enteritis-jejunitis'''.(Merck)

*'''Secondary causes:''' primary intestinal ileus or small or large intestinal obstruction.  Dilation resulting from small intestinal obstruction is the most common cause.  Fluid from the obstructed small intestine accumulates in the stomach, causing [[Colic Diagnosis - Naso-gastric Intubation|naso-gastric reflux]].  Gastric dilation may also occur with certain colonic displacements, especially '''right dorsal displacement of the colon''' around the caecum.  It is hypothesised that the displaced colon obstructs duodenal outflow.  Gastric fluid accumulation is also characteristic of '''proximal enteritis-jejunitis'''.<ref name="Merck">Merck & Co (2008) '''The Merck Veterinary Manual (Eighth Edition)''', ''Merial''.</ref>

Untreated, gastric dilation can rapidly lead to '''gastric rupture''' whereby the stomach usually tears along its greater curvature.  It has been proposed that the '''seromuscularis''' weakens and tears before the gastric mucosa(146,148). Most cases of rupture occur secondary to mechanical obstruction, ileus, and trauma.  The rest are due to overload or idiopathic causes.(Merck)  Rupture can occur secondary to [[Gastric Ulceration - Horse|gastric ulceration]], in which case full-thickness tearing usually occurs in all layers of the gastric wall.(Sanchez)  Certain '''risk factors''' have been identified for gastric rupture(146, 148) including:

Untreated, gastric dilation can rapidly lead to '''gastric rupture''' whereby the stomach usually tears along its greater curvature.  It has been proposed that the '''seromuscularis''' weakens and tears before the gastric mucosa(146,148). Most cases of rupture occur secondary to mechanical obstruction, ileus, and trauma.  The rest are due to overload or idiopathic causes.<ref name="Merck">Merck & Co (2008) '''The Merck Veterinary Manual (Eighth Edition)''', ''Merial''.</ref> Rupture can occur secondary to [[Gastric Ulceration - Horse|gastric ulceration]], in which case full-thickness tearing usually occurs in all layers of the gastric wall.(Sanchez)  Certain '''risk factors''' have been identified for gastric rupture(146, 148) including:

*Feeding grass hay

*Feeding grass hay

*Not feeding grain

*Not feeding grain