Experimental and Clinical Necrotizing Enterocolitis

Abstract: Necrotizing enterocolitis (NEC), a severe inflammatory disorder of the gastrointestinal tract with high morbidity and mortality, affects primarily preterm infants. The diagnosis represents a challenging task, and no biomarker has been found to aid early diagnosis with high accuracy. Microdialysis has been widely used to detect metabolites of anaerobic metabolism, enabling a local and early detection of ischemia. This thesis aims to evaluate the possibility of detecting intestinal ischemic stress in experimental and clinical  NEC, by use of rectal intraluminal microdialysis.Intraluminal rectal microdialysis was performed on rats subjected to total intestinal ischemia. Metabolites of ischemia were detectable in both ileum and rectum, with raised glycerol concentrations and lactate/pyruvate ratios. Elevated concentrations of glycerol correlated to increasing intestinal histopathological injury.Experimental early NEC was induced in newborn rat pups, by hypoxia/re-oxygenation treatment. Development of NEC was confirmed by histopathology. Elevated glycerol concentrations were detected by rectal microdialysis.The genetic alterations following experimental NEC in rat pups were studied with microarray. Immunohistochemistry staining was performed for tight junction proteins claudin-1 and claudin-8. Several genes were altered in experimental NEC, mainly genes regulating tight junctions and cell adhesion. Immunohistochemistry revealed reduced expression of claudin-1.A prospective study was conducted on preterm infants with a gestational age of less than 28 weeks. The infants were admitted to a neonatal intensive care unit, and observed during a 4-week period. Rectal microdialysis was performed twice a week, and blood was drawn for analysis of I-FABP. A total of 15 infants were included in the study, whereof four infants developed NEC, and 11 served as controls. Rectal glycerol and I-FABP displayed high concentrations, which varied considerably during the observation periods, both in NEC and controls. No differences in either glycerol or I-FABP concentrations were seen in the NEC-group vs. the controls.In conclusion, rectal microdialysis can detect metabolites of intestinal ischemia, both in experimental and clinical NEC. Rectal microdialysis is safe and could provide a valuable non-invasive aid to detect hypoxia-induced intestinal damage or ischemic stress in extremely preterm infants. In this study however, it was not possible to predict the development of clinical NEC using microdialysis or I-FABP.