Changes

Simple obstructions of the large intestine produce milder clinical signs compared to the small intestine and have a slower rate of deterioration. Partial obstructions allow for the passage of some ingesta and gas and hence the clinical signs and level of dehydration are milder as some ingesta and water can pass into the caecum. If the obstruction becomes complete, the gas and ingesta cannot pass and cause intestinal distention. This exerts a pressure on the diaphragm which impairs pulmonary function and inhibits the venous return to the heart by compressing of the vena cava. If these cases are untreated, the distention can become so marked that there is a fatal risk of rupture of the devitalised portions of colon or caecum.   

Simple obstructions of the large intestine produce milder clinical signs compared to the small intestine and have a slower rate of deterioration. Partial obstructions allow for the passage of some ingesta and gas and hence the clinical signs and level of dehydration are milder as some ingesta and water can pass into the caecum. If the obstruction becomes complete, the gas and ingesta cannot pass and cause intestinal distention. This exerts a pressure on the diaphragm which impairs pulmonary function and inhibits the venous return to the heart by compressing of the vena cava. If these cases are untreated, the distention can become so marked that there is a fatal risk of rupture of the devitalised portions of colon or caecum.   

===Strangulating Infarction===

===Strangulating Infarction===

Strangulating infarctions have all the same pathological features as a simple obstruction, but the bloody supply is immediately affected. Both arteries and veins may be effected immediately, or progressively as in simple obstruction. Common causes of strangulating obstruction are pedunculated lipomas, and displacement of intestine through a hole, such as a [[hernia]], a mesenteric rent, or the [[epiploic foramen]].

Strangulating infarctions have all the same pathological features as a simple obstruction, but the bloody supply is immediately affected and so they often present as an acute abdominal crisis. The patholphysiological changes are more acute and severe and the mortality rate of cases that go to surgery, is high. Common causes of strangulating obstruction are incarcerations, intussusceptions and intestinal volvulus.

===Non-strangulating Infarction===

===Non-strangulating Infarction===

In a non-strangulating infarction, blood supply to a section of intestine is occluded, without any obstruction to ingesta present within the intestinal lumen.  The most common cause is infection with ''Strongylus vulgaris'' larvae, which develop within the (primarily cranial) [[mesenteric artery]].

In a non-strangulating infarction, blood supply to a section of intestine is occluded, without any obstruction to ingesta present within the intestinal lumen.  The most common cause is infection with ''Strongylus vulgaris'' larvae, which develop within the (primarily cranial) [[mesenteric artery]].