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Abdominal exploration allows for definitive diagnosis and assessment of the extent of disease while at the same time providing opportunity for correction. Characteristically, deep purple to black intestine is noted wherever vasculature is compromised. Compromised blood flow through the cranial mesenteric artery and its branches leads to ischemic injury in the distal duodenum, jejunum, ileum, cecum, ascending and proximal descending colon [2]. With complete mesenteric torsion, there will typically be a very ischemic to necrotic appearance to the intestine with twisting at the root of the mesentery (Figure 9.4). A segmental intestinal volvulus may result in a smaller portion of intestine appearing affected (Figure 9.5). The root of the mesentery should be identified and evaluated for orientation of volvulus and anatomic abnormalities (adhesions or malformations) that may have contributed to the pathology. The volvulus may be 180 degrees to greater than 360 degrees and has been reported to occur either clockwise or counterclockwise [9, 18]. A full abdominal exploration is indicated to ensure that gastric volvulus or splenic torsion has not occurred concurrently, and to assess for other pathology that may have contributed to gastrointestinal disease.

Figure 9.4 Postmortem photograph of a dog with complete mesenteric torsion. Twisting is apparent at the level of the mesenteric root.

Source: University of Minnesota Veterinary Diagnostic Laboratory, Minneapolis, MN. Reproduced with permission from University of Minnesota Veterinary Diagnostic Laboratory.

Figure 9.5 Intraoperative photograph of a dog with intestinal volvulus involving a portion of the small intestine. Note the marked difference between the appearance of normal intestine and the affected portion.

Correction of intestinal volvulus may be accomplished by derotation alone or derotation with resection and anastomosis. Resection before derotation may minimize injury secondary to reperfusion and release of free radicals or other harmful factors into general circulation. Resection before derotation is more feasible when a segmental volvulus is encountered, or when a clear delineation of a relatively short portion of compromised bowel is identified. Performance of intestinal resection after derotation may allow for more rapid perfusion to partially compromised tissues that may have a chance of ultimate viability. Gradual derotation of the intestine may reduce the rate of perfusion and lessen the consequences of reperfusion [30]. Even after derotation and several minutes of perfusion, the surgeon may be faced with the decision to perform radical intestinal resection. Bowel that remains black, thin, cool to the touch, or has no return of arterial pulses should be resected. With complete volvulus, the extent of compromised tissue may be so great as to result in short bowel syndrome (if more than 70–85% of the intestines must be resected) [31–33] or may render resection incompatible with normal physiologic function and life. Following correction of volvulus, the abdomen is thoroughly flushed to minimize residual contamination from bacterial translocation or intraoperative contamination.