Evaluation and graduation of histomorphological changes in ischemic small or large intestine regions after strangulation – a field study

Klinische Feldstudie zur Evaluierung und Graduierung histomorphologischer Veränderungen ischämischer Dünn- oder Dickdarmregionen nach Strangulation

Breitesten M, Werhahn H, Hell H, Snyder A, Schusser G F, Theiß T, Schoon H-A, Barsnick R, Walliser U, Scheidemann W, Bienert A, Donandt D, Stadtbäumer G

DOI: 10.21836/PEM20150603
Year: 2015
Volume: 31
Issue: 6
Pages: 559-570

The purpose of this clinical field study was to examine histologically the ischemic strangulated section of the intestine in colic horses to graduate the epithelial alteration. It was additionally investigated whether a correlation exists between the degree of damages and the duration of colic, the length of the damaged section of the intestine, the causes of colic and clinical outcome. Based on the histological findings conclusion about the necessity for a small bowel resection was drawn. Therefore, intestinal specimens of 89 horses were examined histologically, including 70 horses with strangulation of the small intestine and 11 horses with strangulation of the colon. 8 horses without bowel disease served as a reference group. The focus of this study, due to the number of samples, was the evaluation of the small intestine. The horses with strangulated small intestine were divided into four groups based on clinical outcome: without surgery attempt euthanized (group I), intraoperatively euthanized (group II), died after intestinal resection (group III) and survivors (observation period corresponded to the hospital stay of 10 days) with successful intestinal resection (group IV). The epithelial alterations, hemorrhages and inflammation were graduated for each sample. In order to obtain a detailed scaling a new grading system was established, which reflects the manifestation of epithelial alteration especially within the crypts. The villi were divided into two regions (villus luminal, villus basal), the crypts into three evaluated regions (crypt luminal, crypt central, crypt basal) and for each region a distinct score 0 (normal) to 5 (complete epithelial loss, degeneration) was evaluated. The epithelial alteration was confirmed to start at the tip of the villus and progresses towards the base of the crypt. The degree of hemorrhages was described by the score 0 (no extravasal erythrocytes) to 4 (most increased numbers of erythrocytes) in four intestinal layers (Lamina propria mucosae, Tela submucosa, Tunica muscularis, Tela subserosa). The inflammation was graded in the Lamina propria mucosae and the Tela submucosa, while a distinction between lymphocytes and neutrophils on one hand and eosinophils on the other has been made. The four groups with small intestinal strangulation obstruction did not differ significantly in respect to their epithelial alterations, hemorrhages in the gut wall and the inflammation. The interstitium-crypt-ratio of the lamina propria mucosae was determined on the basis of area and distance measurements. The distance measurements were carried out at three different levels (crypt luminal, crypt central, crypt basal) and each was compared to the results of the area measurement. Instead of the elaborate area measurement, the simpler distance measurement at the center of the crypt can be used to determine the interstitium-crypt-ratio. The duration of colic in horses of group IV (survivors after successfully performed resection) was shorter than those of group III (died after resection). The length of the ischemic section of the small intestine was significantly longer in horses which did not survive after resection (group III) than in group IV. Based on our grading system 24 (= 42.1%)/57 horses in groups II, III and IV had epithelial alterations in the luminal region of the crypt >3/5 which a regeneration may not be likely therefore the resection or the euthanasia of horses were feasible. But based on the grading system of Van Hoogmoed et al. (2000) the epithelial alterations were graded 5/5 in 52 (74.3%)/70 horses with ischemic strangulated small intestine which was not viable. The epithelial alterations of ischemic colon in all horses were graded 5/5 which means no capability of epithelial regeneration. The survival of a horse with small or large intestine strangulation obstruction depends on colic duration (shorter than 6 hours), involved length of ischemic section (shorter than 3 meters), the epithelial alterations (<3/5), the reperfusion injuries (less or no impairment), the circulation (no severe dehydration preoperatively) and the postoperative complications (without peritonitis, adynamic ileus, wound healing problems).