Perioperative neorectal ischemia. Experimental model
Authors:   I.M.Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russian Federation, Morozov D.D. , Morozova O.L. ,   I.M.Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russian Federation, Severgina L.O. ,   I.M.Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russian Federation, Marchuk T.D. ,   I.M.Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russian Federation, Tarasova D.S. ,   I.M.Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russian Federation, Morozov D.A. ,   I.M.Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russian Federation
Published: December 2020

Objective. To experimentally determine and analyze the role of perioperative tissue tension in the intestinal area brought down to the proper topographic and anatomical position (neorectum) and its vascularization impairments during anorectoplasty. Materials and methods. This experiment performed on laboratory rats consisted of 3 parts: clinical (creation of an operation model and assessment of clinical parameters in the early postoperative period); morphological (histological examination of biopsy specimens taken from the surgical area); and laboratory (measurement of tissue hypoxia markers (including vascular endothelial growth factor-C (VEGF-C) and hypoxia-induced factor 1-alpha (HIF-1-alpha)) in serum and intestinal homogenate using enzyme-linked immunosorbent assay (ELISA) (specimens were collected 3 days postoperatively). Forty laboratory rats weighing from 370 to 550 g (mean weight 482 g) were divided into four equal groups: group I – ‘impaired neorectal vascularization;’ group II – ‘neorectal tension;’ group III – ‘rectal replantation;’ and the control group. During the first stage of the experiment (3 days), we assessed overall condition of the animals, number of stools, type of defecation, and pain severity. The animals received no treatment in the postoperative period. On day 3, all rats were euthanized. Tissue specimens were collected from the neorectum to evaluate its morphological characteristics and to produce intestinal homogenate for subsequent ELISA. Blood specimens were obtained by puncturing the left ventricle and then centrifuged at 3000g for 15 minutes. Blood supernatants and neorectum tissues were stored at -80°C for maximum 1 month before testing. Intestinal tissue samples for histological examination were stored in a 10% formalin solution. The levels of hypoxia biomarkers were measured in serum and intestinal homogenate using the Stat Fax 2100. Data analysis was conducted using the SPSS software (with no preliminary calculation of the sample size). We used the Mann–Whitney U-test [H.B.Mann, D.R.Whitney] and Kruskal–Wallis test [W.Kruskall, W.A.Walles]. The differences were considered significant at р < 0.05. Results. The most common morphological changes were caused by impaired vascularization of the rectum. We have found a significant increase (p < 0.001) in the levels of hypoxia markers in intestinal homogenates in all three experimental compared to controls. However, there was no significant difference in the levels of these markers between the experimental groups. The defecation process was abnormal in rats from groups I and II. Conclusion. In anorectoplasty, excessive mobilization of the rectum with its improper vascularization and formation of the anus under conditions of intestinal tissue tension lead to perioperative neorectal ischemia. This experiment should be continued to evaluate long-term results. The proposed models of perioperative neorectal ischemia can be used to analyze the role of many factors that can potentially affect the outcome of anorectal malformation correction. In the future, this problem may be investigated in clinical studies. Key words: anorectal malformations, perioperative ischemia, neorectum, tension, devascularization