Introduction: Classical methods do not allow to rapidly quantify the heterogeneously distributed ischemia-reperfusion injury along the small intestine. We therefore established a suitable macroscopic score.
Methods: A rat model based on superior mesenteric artery occlusion (45 or 90 min ischemia; 0, 120, or 180 min reperfusion) was used on 42 rats.
Results: Subsequent to ischemia-reperfusion or pure ischemia, macroscopic phenotypes of the small intestine were defined and differentiated based on the severity of existing petechiae and hemorrhages (macroscopic types 0-1-2-3). Analysis of the interobserver variability verified the reliability of this macroscopic differentiation. Macroscopic types were directly correlated with their histological alterations (Chiu score). On the basis of the sample hemoglobin content, a nonlinear macroscopic score (0-1-3-9) was derived from the linearly related macroscopic types. Mean macroscopic scores after 45 min ischemia/180 min reperfusion were lower than those after 90 min ischemia/120 min reperfusion. Nevertheless, all scores correlated well with their respective hemoglobin contents (R(2) = 0.87). Heterogeneous patterns of macroscopic scores that depended on the ischemic period and largely differed between individual animals were found to be distributed along the small intestine with the highest injury score at the last half of the jejunum. The iron chelator deferoxamine mesylate clearly decreased the overall tissue hemoglobin content and macroscopic score of the small intestine but local protection was restricted to the proximal and middle part of the jejunum.
Conclusion: The local as well as overall ischemia-reperfusion injury in the rat small intestine can be rapidly and reliably assessed macroscopically.