A Clinical Grading System for Intraoperative Assessment of Small Intestinal Viability in the Horse

Survival after small intestinal surgery in horses has been reported as poor, although there is growing evidence that more recent survival rates are improving. The most common cause of death during hospitalization in three large retrospective studies were anastomotic leakage, septic peritonitis, and shock. Adhesions accounted for most long-term deaths in two studies, and volvulus, adhesions, and malabsorption syndrome accounted for most long-term deaths in another. Adhesions are reported with a prevalence of 6–26% after small intestinal surgery, with an apparent decline in prevalence in more recent reports. The severity of serosal damage inflicted in remaining bowel by distention and combined ischemia and reperfusion has been incriminated in the development of adhesions in equine small intestine. More severe mural changes caused by venous occlusion, such as hemorrhage and edema, have been demonstrated as a cause of adhesions in horses in an experimental setting. However, experimental design could play a large part in formation of such adhesions, because an association between similar mural changes and adhesions was not demonstrated in another study on ponies. This issue is important in equine small intestinal surgery, because it expands the definition of nonviable bowel to include small intestine that could survive an ischemic insult but subsequently form lifethreatening adhesions. A serious concern with this definition is the risk of unnecessary intestinal resection, which is associated with potential problems, including adhesions, expense, and longer surgery time. An overly pessimistic approach to intestinal viability could also lead to euthanasia in horses in which the option of resection is eliminated by prevailing conditions, such as lack of expertise, equipment, financial resources, inaccessibility of the affected segment, or involvement of too much bowel to allow normal intestinal function. This study was designed as a retrospective evaluation of a clinical grading system used to assess intestinal viability in horses that had small intestinal strangulating lesions. Short-term and long-term outcomes were used to assess responses