Necrotizing enterocolitis: pathophysiology and prevention

Gastroschisis in the neonatal period: A prospective case-series in a Brazilian referral center

BACKGROUND/PURPOSE

Gastroschisis is increasing in incidence and has low mortality and high morbidity. We describe the clinical and surgical characteristics of gastroschisis patients in a Brazilian referral center.

METHODS

Single-center prospective case series of gastroschisis patients. The following two groups were formed depending on the intestinal characteristics: simple and complex patients.

RESULTS

In total, 79 patients were enrolled, 89% of whom were classified as simple and 11% as complex. The baseline characteristics were similar between the groups, with the exception of the illness severity score. The complex group had a significantly smaller defect size, more reoperations and worse clinical outcomes than the simple group, with the initiation of feeding taking 1.5 times longer, the duration of total parenteral nutrition taking twice as long, and the length of hospitalization being 2.5 times longer; the complex group also included all the deaths that occurred. Overall, the survival rate was 96%. Patients who underwent the sutureless technique had significantly fewer wound infections and a decreased duration of mechanical ventilation than sutured patients.

CONCLUSIONS

This study provides a comprehensive picture of gastroschisis during the neonatal period in a Brazilian referral center, emphasizing the significantly higher risk for morbidity and mortality among complex patients than among simple patients and the few advantages of the sutureless technique over the sutured technique in terms of closing the defect.

TYPE OF STUDY

Prognostic.

LEVEL OF EVIDENCE

IV.

Histological analysis of the intestinal wall of newborn rats submitted to hypoxia and reoxygenation to evaluate the protective effect of N-Acetylcysteine

Purpose

To evaluate the effect of N-Acetylcysteine (NAC) in newborn rats submitted to hypoxia and reoxygenation (H/R) conditions in an experimental model of necrotizing enterocolitis.

Methods

Eight pregnant rats and their 70 cubs were used (5 groups) and exposed to H/R conditions and received NAC at different times. The animals in the H/R groups were placed in a gas chamber (100% CO²) for 10 minutes and then reoxygenated for 10 minutes (100% O²), twice a day for the first three days of life, with a six-hour span between events. On the third day of life, the animals were anesthetized, laparotomized and the intestines were resected.

Results

The H/R and NAC groups showed changes in the intestinal wall in relation to the number, height and width of the villi when compared to the control group (p<0.0001), but with better preservation of structures in the NAC group. There were no differences between groups regarding the number (%) of mitoses.

Conclusion

The administration of NAC decreased the lesions in the intestinal wall of rats submitted to H/R, therefore suggesting that this drug can be used to prevent the development of necrotizing enterocolitis in newborns.

Bifidobacterium and Lactobacillus for preventing necrotizing enterocolitis in very-low-birth-weight preterm infants: a systematic review and meta-analysis

BACKGROUND

The therapeutic effect of Bifidobacterium and Lactobacillus on necrotizing enterocolitis (NEC) in very-low-birth-weight preterm infants was controversial, and we aimed to explore the exact impact of the two probiotics.

METHODS

The PubMed, EMBASE, Web of Science and Cochrane Library were systematically searched for studies published from January 1, 2010 to February 28, 2019. Results were combined with fixed-effect model or random-effect model with specific conditions. Sensitivity analysis was conducted by the trim-and-fill method, and the Begger's and Egger's test were used to measure publication bias.

RESULTS

The meta-analysis included 16 original articles with 4632 very-low-birth-weight preterm infants. With respect to the intervention of Bifidobacterium, we estimated non-significant decrease in the morbidity of NEC with a risk ratio (RR) of 0.75 [95% confidence internal (CI) 0.56-1.01, P = 0.06]. Regarding the effect of Lactobacillus, there was no evidence of significant lower risk in the incidence of NEC (RR = 0.67, 95% CI 0.39-1.17, P = 0.16). The use of mixture of probiotics (Bifidobacterium and Lactobacillus) reduced the risk of NEC in the probiotics group (RR = 0.45, 95% CI 0.25-0.80, P = 0.007).

CONCLUSION

The mixture of Bifidobacterium and Lactobacillus could prevent the morbidity of NEC in very-low-birth-weight preterm infants. But Bifidobacterium or Lactobacillus alone did not show this effect.

Is mode of delivery associated with the risk of necrotizing enterocolitis?

BACKGROUND

The pathogenesis of necrotizing enterocolitis remains poorly understood. Different newborn bacterial colonization due to cesarean delivery as opposed to vaginal delivery has been implicated as one potential contributing factor.

OBJECTIVE

We sought to determine whether mode of delivery is associated with the risk of necrotizing enterocolitis in neonates of women who were at imminent risk of delivery <32 weeks' gestational age.

STUDY DESIGN

This is a secondary analysis of data from a randomized controlled trial of magnesium sulfate for the prevention of cerebral palsy. The parent trial included women with pregnancies at 24 to 31 6/7 weeks of gestation who were considered at imminent risk for preterm delivery. Women with a viable singleton gestation and data available on mode of delivery and development of necrotizing enterocolitis were included. Neonates delivered by vaginal delivery were compared to those delivered by cesarean delivery in bivariable analyses. Multivariable analysis was used to adjust for potential confounders.

RESULTS

A total of 2012 mother-neonate pairs were analyzed. Of these, 731 (36%) women delivered by cesarean delivery and 170 neonates (8.4%) developed necrotizing enterocolitis. In bivariable analyses, women who delivered by cesarean delivery were older (27 [interquartile range, 22-32] vs 24 [interquartile range, 20-29] years, P < .001) and had a higher frequency of chorioamnionitis (14.0% vs 10.5%, P = .021) compared to those who delivered vaginally. Neonates delivered by cesarean delivery were more premature (29.3 [interquartile range, 27.1-31.4] vs 30.3 [interquartile range, 27.9-31.9] weeks, P < .001), were smaller (1266 [interquartile range, 920-1643] vs 1465 [interquartile range, 1067-1850] g, P < .001), were more likely to be small for gestational age (4.4% vs 1.9%, P = .001), and had a higher frequency of proven sepsis (20.1% vs 14.7%, P = .002) compared to those who delivered vaginally. Rates of necrotizing enterocolitis (8.1% vs 8.7%, P = .65) and stage 2 or 3 necrotizing enterocolitis (4.4% vs 4.7%, P = .75) did not differ by mode of delivery. After adjusting for potential confounders, cesarean delivery continued to have no association with the frequency of necrotizing enterocolitis (adjusted odds ratio, 0.74; 95% confidence interval, 0.52-1.04) or stage 2 or 3 necrotizing enterocolitis (adjusted odds ratio, 0.73; 95% confidence interval, 0.46-1.16). This study was powered to detect a minimum relative risk of 1.5 for necrotizing enterocolitis associated with mode of delivery.

CONCLUSION

Mode of delivery was not significantly associated with necrotizing enterocolitis in neonates born to a cohort of women who were considered at imminent risk of extreme preterm delivery.

Gut microbiota and the pathogenesis of necrotizing enterocolitis in preterm neonates

Necrotizing enterocolitis (NEC) remains a devastating intestinal disease in preterm neonates. In this population, disruption of the gut microbiota development, mainly due to organ immaturity, antibiotic use and hospital microbial environment, plays a key role in the pathogenesis of NEC. This gut dysbiosis has been associated with opportunistic pathogens overgrowth, expression of virulence factors, altered metabolic functions and inflammatory dysregulated responses. In this review, we provide an updated summary of the host and gut microbiota interactions during the formative early life. We also explore the key determinants of gut dysbiosis in preterm neonates with NEC. Finally, we discuss the promising role of bacteriotherapy in the management of NEC, the aim being to shape or restore the beneficial gut bacterial communities.

Small intestinal lactoferrin and calprotectin levels in different stages of necrotizing enterocolitis in a rat model

PURPOSE

Necrotizing enterocolitis (NEC) is a severe disease of mostly premature infants with high morbidity and mortality rates. There is no reliable biomarker for detecting newborns at risk for NEC development. We aimed to investigate small intestinal lactoferrin (LF) and calprotectin (CAL) levels as predictors and indicators of disease severity in an experimental newborn rat model.

MATERIALS AND METHODS

Newborn pups were randomly divided into two groups, NEC and control. The NEC group pups were decapitated on the second, third and fourth days of the experiment for an assessment of the different stages of NEC. In the study group, hypoxia-reoxygenation model used to induce NEC. As biochemical parameters, small intestinal LF and CAL levels were measured with an enzyme-linked immunosorbent assay technique and intestinal injury scoring was evaluated as a pathologic parameter.

RESULTS

Small intestinal levels of both LF and CAL increased in the second and the third day groups, but began to decrease by the fourth day. The first, second and third day levels of LF and CAL were higher than controls. The intestinal injury scores of all NEC groups were significantly higher than the control group.

CONCLUSION

Small intestinal lactoferrin and calprotectin were good markers for demonstrating NEC. However, instead of spot testing, monitoring the levels of these markers may be more informative.

Use of pigs as a potential model for research into dietary modulation of the human gut microbiota

The human intestinal microbial ecosystem plays an important role in maintaining health. A multitude of diseases including diarrhoea, gastrointestinal inflammatory disorders, such as necrotising enterocolitis (NEC) of neonates, and obesity are linked to microbial composition and metabolic activity. Therefore, research on possible dietary strategies influencing microbial composition and activity, both preventive and curative, is being accomplished. Interest has focused on pre- and probiotics that stimulate the intestinal production of beneficial bacterial metabolites such as butyrate, and beneficially affect microbial composition. The suitability of an animal model to study dietary linked diseases is of much concern. The physiological similarity between humans and pigs in terms of digestive and associated metabolic processes places the pig in a superior position over other non-primate models. Furthermore, the pig is a human-sized omnivorous animal with comparable nutritional requirements, and shows similarities to the human intestinal microbial ecosystem. Also, the pig has been used as a model to assess microbiota–health interactions, since pigs exhibit similar syndromes to humans, such as NEC and partly weanling diarrhoea. In contrast, when using rodent models to study diet–microbiota–health interactions, differences between rodents and humans have to be considered. For example, studies with mice and human subjects assessing possible relationships between the composition and metabolic activity of the gut microbiota and the development of obesity have shown inconsistencies in results between studies. The present review displays the similarities and differences in intestinal microbial ecology between humans and pigs, scrutinising the pig as a potential animal model, with regard to possible health effects.

Role of neutrophils and macrophages in the pathogenesis of necrotizing enterocolitis caused by Cronobacter sakazakii

BACKGROUND

Cronobacter sakazakii (CS) is a highly virulent gram-negative opportunistic pathogen that has been implicated in clinical outbreaks of necrotizing enterocolitis (NEC). The role of mucosal immune cells in CS infection is not well understood. In this study, we sought to elucidate the role of neutrophils (polymorphonuclear leukocytes; PMNs) and macrophages in the pathogenesis of NEC induced by CS using a novel newborn mouse model.

MATERIALS AND METHODS

PMNs and macrophages were depleted in newborn mice using Gr-1 antibody and carrageenan, respectively, and then infected with 10(3) CFU of CS. The development of NEC in these mice was assessed by a pathologist based on the morphologic changes in the intestine. Cytokine production was determined in the serum and intestinal homogenates of infected mice by enzyme-linked immunosorbent assay (ELISA). Inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production was determined by flow cytometry and Greiss method, respectively.

RESULTS

Depletion of PMNs and macrophages in newborn mice led to increased recruitment of dendritic cells (DCs) in the intestine compared with wild-type mice upon infection with CS. PMN- and macrophage-depleted mice showed increased bacterial load, production of pro-inflammatory cytokines, iNOS expression, and NO production in the intestines in comparison to wild-type mice fed with CS. In addition, depletion of PMNs and macrophages prior to infection in mice resulted in severe inflammation, villus destruction, and enhanced enterocyte apoptosis in the intestines compared with CS-infected wild-type mice.

CONCLUSIONS

Our data suggest that depletion of PMNs and macrophages from the lamina propria (LP) exacerbates experimental NEC, indicating that both of these immunocytes play an important role in the clearance of CS during the initial stages of infection. The increased mucosal cytokine response and NO production in the absence of these immunocytes may be responsible for the observed increase in mucosal injury. Understanding how CS manipulates these cells, employing novel mouse model of NEC reported in this study, will provide significant insights for the development of novel therapeutic and preventive strategies to combat NEC.

Nutritional modulation of the gut microbiota and immune system in preterm neonates susceptible to necrotizing enterocolitis

The gastrointestinal inflammatory disorder, necrotizing enterocolitis (NEC), is among the most serious diseases for preterm neonates. Nutritional, microbiological and immunological dysfunctions all play a role in disease progression but the relationship among these determinants is not understood. The preterm gut is very sensitive to enteral feeding which may either promote gut adaptation and health, or induce gut dysfunction, bacterial overgrowth and inflammation. Uncontrolled inflammatory reactions may be initiated by maldigestion and impaired mucosal protection, leading to bacterial overgrowth and excessive nutrient fermentation. Tumor necrosis factor alpha, toll-like receptors and heat-shock proteins are identified among the immunological components of the early mucosal dysfunction. It remains difficult, however, to distinguish the early initiators of NEC from the later consequences of the disease pathology. To elucidate the mechanisms and identify clinical interventions, animal models showing spontaneous NEC development after preterm birth coupled with different forms of feeding may help. In this review, we summarize the literature and some recent results from studies on preterm pigs on the nutritional, microbial and immunological interactions during the early feeding-induced mucosal dysfunction and later NEC development. We show that introduction of suboptimal enteral formula diets, coupled with parenteral nutrition, predispose to disease, while advancing amounts of mother's milk from birth (particularly colostrum) protects against disease. Hence, the transition from parenteral to enteral nutrition shortly after birth plays a pivotal role to secure gut growth, digestive maturation and an appropriate response to bacterial colonization in the sensitive gut of preterm neonates.

Can we cut the incidence of necrotizing enterocolitis in half--today?

Necrotizing enterocolitis (NEC) is a common gastrointestinal emergency of neonates. Population studies estimate the incidence of NEC at between 0.3 and 2.4 per 1000 live births in the United States, with a predominance of cases among preterm neonates born at the earliest gestational ages. The disease burden of NEC includes an overall disease-specific mortality rate of 15-20%, with yet higher rates in those of earliest gestations. The NEC burden also includes an increase in hospital costs approximating $100,000/case, as well as severe late sequellae including parenteral nutrition-associated liver disease and short bowel syndrome. Differentiating NEC from other forms of acquired neonatal intestinal disease is critical to assessing the success of NEC prevention strategies. Promising new prevention strategies are now being tested; one such is prophylactic heparin-binding epidermal growth factor-like growth factor (HB-EGF) administration. However, two prevention strategies have already been shown in meta-analyses to reduce the incidence of NEC, but we speculate that these are not being fully utilized. They are; 1) implementing a written set of feeding guidelines (also called standardized feeding regimens) for newborn intensive care unit (NICU) patients, and 2) implementing programs to increase the availability of human milk for patients at risk of developing NEC.

Do lesions of the enteric nervous system occur following intestinal ischemia/reperfusion?

PURPOSE

To evaluate tissue lesions, especially those of the intestinal innervation, in an excluded jejunal loop subjected to ischemia and reperfusion in rats.

METHODS

To evaluate the role of ischemia and reperfusion lesions in an excluded intestinal loop, four groups of 20 rats were set up: control group (GCEI7) and three experimental groups (GIREI7, GIREI14 and GIREI28). They were all subjected to exclusion of an intestinal segment of six centimeters in length, at a distance of 10 centimeters from the Treitz angle. The 60 animals in the three experimental groups were additionally subjected to ischemia of the vascular pedicle for 30 minutes. The control group and the experimental group GIREI7 were evaluated on the 7th day after the operation. The groups GIREI14 and GIREI28 (which also underwent ischemia) were utilized to evaluate the evolution of the lesion over time, on the 14th and 28th days after the operation, respectively. From the intestinal excluded loop, we take one ring of 0,5 cm distal and proximal, that were fixed in formaline 10% solution in order to do histological (HE) and immuno-hystochemial (PS-100) evaluation (enteric nervous system.) The distal loop was exteriorized in stoma and the proximal part closed with polipropilene 6-0.

RESULTS

It was observed a decrease in the number of ganglionic cells in the myenteric plexus in the group subjected to ischemia and reperfusion (GIREI7), in relation to the control group (GCEI7) at the 7th post-operative day (Mann-Whitney test: p = 0.0173 *. Comparing the numbers of ganglionic cells in the myenteric plexus before and after jejunal loop exclusion GCEI7 - (Wilcoxon test: p = 0.0577). GIREI7 - Comparing the numbers of ganglionic cells in the myenteric plexus before and after ischemia (*p = 0.0399). Comparing the percentage variations in ganglionic cells in the myenteric plexus on the 7th, 14th and 28th days after the procedure, in the groups GIREI7, GIREI14 and GIREI28, it was observed that there were no significant alterations. Kruskal-Wallis test: p = 0.6501.

CONCLUSION

There was a decrease in the number of ganglionic cells in the myenteric plexus due to ischemia and reperfusion that did not recover in the late post-operative period.

Nosocomial infection in small for gestational age newborns with birth weight <1500 g: a multicentre analysis

OBJECTIVE

To investigate whether preterm newborns who are small for gestational age are at increased risk of nosocomial infections and necrotising enterocolitis.

DESIGN, SETTING AND SUBJECTS

The German national surveillance system for nosocomial infection in very low birthweight infants uses the US Centers for Disease Control and Prevention criteria. 2918 newborns (24-28 weeks), born between 2000 and 2004, were selected after application of predefined inclusion criteria to ensure similar proportions of small and appropriate weight for gestational age newborns across gestational age groups.

MAIN OUTCOME MEASURES

The outcome criterion was at least one episode of nosocomial sepsis, pneumonia or necrotising enterocolitis. Adjusted odds ratios and corresponding 95% CIs were calculated based on general estimating equation models.

RESULTS

The study population consisted of 13% (n = 392) small and 87% (n = 2526) appropriate weight for gestational age infants. 33% (n = 950) of the infants experienced at least one episode of sepsis: 42% (n = 163) of small and 31% (n = 787) of appropriate weight for gestational age newborns (adjusted OR 1.41, 95% CI 1.05 to 1.89). Pneumonia was diagnosed in 6% (n = 171) of infants: 8.4% (n = 33) of small and 5.5% (n = 138) of appropriate weight for gestational age newborns (adjusted OR 1.57, 95% CI 1.19 to 5.57). Necrotising enterocolitis was documented in 5.2% (n = 152) of infants: 7.1% (n = 28) of small and 4.9% of (n = 124) appropriate weight for gestational age newborns (adjusted OR 1.20, 95% confidence interval 0.75 to 1.94).

CONCLUSIONS

Growth-retarded preterm infants seem to be at increased risk of nosocomial infection, irrespective of the responsible pathogen. Future immunological research should elucidate potential causal associations.

Sonographic findings in a model of ischemia-induced necrotizing enterocolitis with pathological correlations

PURPOSE

To evaluate sonographic findings in ischemic enterocolitis (IEC) and correlate with pathologic findings in an experimental study.

MATERIALS AND METHODS

Ischemic enterocolitis was induced with ligation of the superior mesenteric artery in 20 rabbits. Plain radiography and ultrasonography (US) were performed. US was done hourly after the ligation using 10 MHz linear probe. US findings were categorized into 2 groups according to the bowel wall echogenicity; the echogenic dots (ED) group and the circumferential granular echogenicity (CGE) group. US findings were compared with the specimen radiography and the histopathology.

RESULTS

On US, ED were seen in the bowel of all rabbits after SMA ligation (2.2 +/- 1.3 hours [standard deviation]) and CGE in 16 rabbits (4.1 +/- 0.9 hours). On the specimen radiographs, multiple radiolucent air bubbles were present. Comparing the ED and CGE group, histopathological findings revealed the CGE group had severer injury of the bowel wall than the ED group. On plain radiography, there was progressive bowel distention, but pneumatosis intestinalis (PI) was not evident.

CONCLUSION

ED or CGE are the sonographic findings of ischemic enterocolitis, and bowel wall echogenicity might reflect the degree of ischemic injury.

Epidermal growth factor reduces hepatic sequelae in experimental necrotizing enterocolitis

BACKGROUND AND AIM

Neonatal necrotizing enterocolitis (NEC) is the most common gastrointestinal disease of premature infants. We recently demonstrated that the gut/liver axis plays an important role in the pathophysiology of NEC through the release of inflammatory mediators into the intestinal lumen. We have also shown that supplementation of formula with epidermal growth factor (EGF) dramatically decreases ileal pathology associated with experimental NEC. In this study, we examined the effects of EGF on the liver portion of the gut/liver axis in the neonatal rat model of NEC.

METHODS

Newborn rats were divided into three experimental groups, NEC, hand-fed with growth-factor free formula; NEC + EGF, hand-fed with formula supplemented with 500 ng/ml rat EGF; or DF, dam fed. All animals were exposed to asphyxia and cold stress twice daily for 4 days to develop NEC.

RESULTS

EGF receptor expression was significantly (p <or= 0.01) decreased in the NEC+EGF group compared to the NEC group. EGF supplementation significantly decreased Kupffer cell numbers (p <or= 0.01) as well as hepatic tumor necrosis factor (TNF)-alpha and interleukin-18 production (p <or= 0.05). Further, TNF-alpha in the intestinal luminal contents of the NEC+EGF group were normalized to levels observed in DF controls compared to the NEC group (p <or= 0.05). Activated nuclear factor-kappaB was also substantially decreased in the NEC+EGF group versus the NEC group.

CONCLUSION

The results of this study indicate that EGF normalizes cytokine overproduction in the liver of neonatal rats with NEC, which contributes to diminished intestinal damage during the development of experimental NEC. These data suggest that supplementation of formula with EGF can have beneficial effects on the gut/liver axis during NEC pathogenesis.

Preterm birth makes the immature intestine sensitive to feeding-induced intestinal atrophy

Preterm birth and formula feeding predispose to small intestinal dysfunction, which may lead to necrotizing enterocolitis (NEC). In piglets, we tested whether the physiological and environmental transitions occurring at birth affect the response of the immature intestine to enteral feeding. Pig fetuses (106 days gestation, term = 115 days) were prepared with esophageal feeding tubes and fed either sow's colostrum (n = 8) or infant formula (n = 7) in utero. After 24 h of oral feeding, the pig fetuses were delivered by cesarean section and their gastrointestinal morphology and function were compared with those of preterm newborn (NB) littermates that were not fed (n = 8) or fed colostrum (n = 7) or formula (n = 13) for 24 h after birth. Before birth, both colostrum and formula feeding resulted in marked increases in intestinal mass, brush-border enzyme activities, and plasma glucagon-like peptide 2 concentrations, to levels similar to those in NB colostrum-fed piglets. In contrast, NB formula-fed piglets showed reduced intestinal growth, decreased brush-border enzyme activities, and intestinal lesions, reflecting NEC. NB formula-fed pigs also showed impaired enterocyte endocytotic function and decreased antioxidative capacity, whereas brush-border enzyme mRNA levels were unaltered, relative to NB colostrum-fed pigs. Our results indicate that the feeding-induced growth and enzyme maturation of the immature intestine are not birth dependent. However, with a suboptimal diet (milk formula), factors related to preterm birth (e.g., microbial colonization and metabolic and endocrine changes) make the immature intestine sensitive to atrophy and development of NEC.

The effects of long-term total parenteral nutrition on gut mucosal immunity in children with short bowel syndrome: a systematic review

BACKGROUND: Short bowel syndrome (SBS) is defined as the malabsorptive state that often follows massive resection of the small intestine. Most cases originate in the newborn period and result from congenital anomalies. It is associated with a high morbidity, is potentially lethal and often requires months, sometimes years, in the hospital and home on total parenteral nutrition (TPN). Long-term survival without parenteral nutrition depends upon establishing enteral nutrition and the process of intestinal adaptation through which the remaining small bowel gradually increases its absorptive capacity. The purpose of this article is to perform a descriptive systematic review of the published articles on the effects of TPN on the intestinal immune system investigating whether long-term TPN induces bacterial translocation, decreases secretory immunoglobulin A (S-IgA), impairs intestinal immunity, and changes mucosal architecture in children with SBS. METHODS: The databases of OVID, such as MEDLINE and CINAHL, Cochran Library, and Evidence-Based Medicine were searched for articles published from 1990 to 2001. Search terms were total parenteral nutrition, children, bacterial translocation, small bowel syndrome, short gut syndrome, intestinal immunity, gut permeability, sepsis, hyperglycemia, immunonutrition, glutamine, enteral tube feeding, and systematic reviews. The goal was to include all clinical studies conducted in children directly addressing the effects of TPN on gut immunity. RESULTS: A total of 13 studies were identified. These 13 studies included a total of 414 infants and children between the ages approximately 4 months to 17 years old, and 16 healthy adults as controls; and they varied in design and were conducted in several disciplines. The results were integrated into common themes. Five themes were identified: 1) sepsis, 2) impaired immune functions: In vitro studies, 3) mortality, 4) villous atrophy, 5) duration of dependency on TPN after bowel resection. CONCLUSION: Based on this exhaustive literature review, there is no direct evidence suggesting that TPN promotes bacterial overgrowth, impairs neutrophil functions, inhibits blood's bactericidal effect, causes villous atrophy, or causes to death in human model.The hypothesis relating negative effects of TPN on gut immunity remains attractive, but unproven. Enteral nutrition is cheaper, but no safer than TPN. Based on the current evidence, TPN seems to be safe and a life saving solution.

Too much short chain fatty acids cause neonatal necrotizing enterocolitis

Nenatal necrotizing enterocolitis (NEC) is a disease mainly affects premature infants. It is well known that prematurity, enteral formula feeding, and bacterial colonization are three major risk factors for NEC. Acetic acid, propionic acid and butyric acid are short chain fatty acids (SCFAs), which are produced mainly in the colon by bacterial fermentation of undigested carbohydrates. Although luminal production of modest quantities of SCFAs is essential for normal colonic mucosal function, excessive production/accumulation of SCFAs may arise in premature infants due to increased luminal carbohydrates malabsorption and poor gastrointestinal motility, and may have deleterious effects on mucosal integrity. Therefore, it is proposed that too much luminal short chain fatty acids cause neonatal NEC.

Resuscitation with 100% oxygen causes intestinal glutathione oxidation and reoxygenation injury in asphyxiated newborn piglets

OBJECTIVE

To compare mesenteric blood flow, oxidative stress, and mucosal injury in piglet small intestine during hypoxemia and reoxygenation with 21%, 50%, or 100% oxygen.

SUMMARY BACKGROUND DATA

Necrotizing enterocolitis is a disease whose pathogenesis likely involves hypoxia-reoxygenation and the generation of oxygen-free radicals, which are known to cause intestinal injury. Resuscitation of asphyxiated newborns with 100% oxygen has been shown to increase oxidative stress, as measured by the glutathione redox ratio, and thus may predispose to free radical-mediated tissue injury.

METHODS

Newborn piglets subjected to severe hypoxemia for 2 hours were resuscitated with 21%, 50%, or 100% oxygen while superior mesenteric artery (SMA) flow and hemodynamic parameters were continuously measured. Small intestinal tissue samples were analyzed for histologic injury and levels of oxidized and reduced glutathione.

RESULTS

SMA blood flow decreased to 34% and mesenteric oxygen delivery decreased to 9% in hypoxemic piglets compared with sham-operated controls. With reoxygenation, SMA blood flow increased to 177%, 157%, and 145% of baseline values in piglets resuscitated with 21%, 50%, and 100% oxygen, respectively. Mesenteric oxygen delivery increased to more than 150% of baseline values in piglets resuscitated with 50% or 100% oxygen, and this correlated significantly with the degree of oxidative stress, as measured by the oxidized-to-reduced glutathione ratio. Two of eight piglets resuscitated with 100% oxygen developed gross and microscopic evidence of pneumatosis intestinalis and severe mucosal injury, while all other piglets were grossly normal.

CONCLUSIONS

Resuscitation of hypoxemic newborn piglets with 100% oxygen is associated with an increase in oxygen delivery and oxidative stress, and may be associated with the development of small intestinal hypoxia-reoxygenation injury. Resuscitation of asphyxiated newborns with lower oxygen concentrations may help to decrease the risk of necrotizing enterocolitis.

Inter-observer reliability of radiological signs of necrotising enterocolitis in a population of high-risk newborns

Radiological examination of the abdomen is critical to the diagnosis of necrotising enterocolitis (NEC). Previous studies on the reproducibility of radiological findings have been limited in size and based only on infants with the disease. We conducted a study among a sample of high-risk infants with and without the diagnosis of NEC: (1) to measure the degree of inter-observer agreement of NEC radiological diagnosis and signs and (2) identify a profile of radiological signs which led the observers to make a diagnosis of NEC. We collected 297 X-rays from a sample of 57 newborns admitted in 1999 to neonatal intensive care and neonatal surgery units in Rome, Italy. Three specialists in paediatric radiology examined the films independently and without any clinical information about patients. The analyses were conducted on a total of 891 forms filled in by the observers. Kappa values were calculated to measure the inter-observer reliability. To identify the profiles of radiological signs, a multidimensional analysis, binary segmentation, was carried out. The reproducibility of radiographic signs was 0.55 (P < 0.01) for diffuse gaseous intestinal distention, 0.22 (P < 0.01) for bowel wall thickening, 0.10 (P < 0.01) for presence of portal venous gas and 0.29 (P < 0.01) for pneumatosis intestinalis. The agreement for radiographic diagnosis suspected/confirmed of NEC was 0.31 (P < 0.01). Among the 23 possible combinations of radiographic signs, the three radiologists indicated four profiles that produced a diagnosis of NEC containing, respectively, two, three, four and five signs. Our study found, in a large sample of radiographs selected from a population of infants with and without NEC, a poor reliability for NEC diagnosis and individual radiological signs among three expert radiologists. Clinical information and the presence of more than one radiological sign can reduce the margin of observer's error that inevitably exists when dealing with a diagnosis as difficult as NEC.

[Necrotizing enterocolitis and apnoeas-bradycardias of the preterm newborn]

We conducted a case control study during six and a half years with the objective to analyse the risk factors for NEC.

POPULATION AND METHODS

All cases of confirmed NEC matched to controls for identical gestational age and period of hospitalization; apnoeas-bradycardias prospectively counted.

RESULTS

Forty-five cases were compared to 89 controls. The isolated risk factors were: an intra-uterine growth retardation (OR = 3,65, 95% confidence interval [CI] 95%: 1,54-8,63); a birth weight < 1000 g (OR = 8,16, CI 95%: 1,17-56,62), compared to a weight >/= 1500 g; a triple antibiotherapy (OR = 6,15, CI 95%: 1,16-32,45); an umbilical venous catheterization (OR = 2,64, CI 95%: 1,09-6,44); a number of simple apnoeas-bradycardias >/= 3rd tercile (n = 27) (OR = 4,54, CI 95%: 1,29-15,93), or severe (stimulated or with hypoxia) apnoeas-bradycardias >/= 3rd tercile (n = 8) (OR = 6,15, CI 95%: 1,59-23,75); an haemoglobin level lower than the 1(st) tercile (95 g/L) (OR = 5,90, CI 95%: 1,20-20,13); and milk thickening by Gumilk (OR = 2,78, CI 95%: 1,11-6,90).

CONCLUSION

In the present practices, anoxo-ischemic factors during the first week of life do not represent an important risk of NEC; a great vigilance must be exercised for indications of the triple antibiotherapy and the treatment of apnoeas-bradycardias.

Neonatal necrotizing enterocolitis: clinical considerations and pathogenetic concepts

Necrotizing enterocolitis (NEC), a disease affecting predominantly premature infants, is a leading cause of morbidity and mortality in neonatal intensive care units. Although several predisposing factors have been identified, such as prematurity, enteral feeding, and infection, its pathogenesis remains elusive. In the past 20 years, we have established several animal models of NEC in rats and found several endogenous mediators, especially platelet-activating factor (PAF), which may play a pivotal role in NEC. Injection of PAF induces intestinal necrosis, and PAF antagonists prevent the bowel injury induced by bacterial endotoxin, hypoxia, or challenge with tumor necrosis factor-a (TNF) plus endotoxin in adult rats. The same is true for lesions induced by hypoxia and enteral feeding in neonatal animals. Human patients with NEC show high levels of PAF and decreased plasma PAF-acetylhydrolase, the enzyme degrading PAF. The initial event in our experimental models of NEC is probably polymorphonuclear leukocyte (PMN) activation and adhesion to venules in the intestine, which initiates a local inflammatory reaction involving proinflammatory mediators including TNF, complement, prostaglandins, and leukotriene C4. Subsequent norepinephrine release and mesenteric vasoconstriction result in splanchnic ischemia and reperfusion. Bacterial products (e.g., endotoxin) enter the intestinal tissue during local mucosal barrier breakdown, and endotoxin synergizes with PAF to amplify the inflammation. Reactive oxygen species produced by the activated leukocytes and by intestinal epithelial xanthine oxidase may be the final pathway for tissue injury. Protective mechanisms include nitric oxide produced by the constitutive (mainly neuronal) nitric oxide synthase, and indigenous probiotics such as Bifidobacteria infantis. The former maintains intestinal perfusion and the integrity of the mucosal barrier, and the latter keep virulent bacteria in check. The development of tissue injury depends on the balance between injurious and protective mechanisms.

Revisiting ischemia and reperfusion injury as a possible cause of necrotizing enterocolitis: Role of nitric oxide and superoxide dismutase

BACKGROUND/PURPOSE

The pathogenesis of necrotizing enterocolitis (NEC) is unknown. Ischemia and reperfusion (I/R) injury has been considered a major contributing factor. Nitric oxide (NO) and superoxide dismutases (SODs) have been shown to protect bowel from I/R injury. This study aims to assess (1) the ability of premature intestine to resist I/R injury compared with mature intestine and (2) the possible role of NO and SODs in modulating such response.

METHODS

Intestines from 5 groups of rats (n = 6 for each study group) were studied: (1) premature, gestational age 20 days; (2) premature, gestational age 22 days; (3) full-term, newborn; (4) infant, day 15; (5) infant, day 30.

EXPERIMENTS

(1) The degrees of I/R injury after 0, 30, 60, 90 and 120 minutes, respectively, of ischemia and 25 minutes of I/R were assessed histologically by a pathologist who was unaware of the operative details. (2) Tissue NO and copper levels were measured by electroparamagnetic resonance (EPR) study; and nitric oxide synthases, copper zinc (CuZn) SODs and manganese (Mn) SODs were examined immunohistochemically. (3) and (4) I/R injury was assessed in rats that had received intraperitoneal injections of L-arginine (NO donor) and L-NAME (NO antagonist), respectively.

RESULTS

For premature (1,2), newborn (3) and mature (4,5) intestines, grades of injury at maximum I/R period studied (120 minutes of ischemia, 25 minutes of reperfusion) were 0, 0, and 3, respectively (P <.05); NO levels were 1 u +/- 1.5, 3 +/- 2.5, and 22 u +/- 3.5, respectively (P <.05); Cu levels were 150 u +/- 15, 200 u +/- 41 and 12 u +/- 2, respectively (P <.05); NOS in intestines were +, +, +++ and CuZnSODs were ++, +++, +, respectively; and MnSODs were +++, ++, -, respectively. No change in NO levels was detected in groups (1), (2), or (3) after L-arginine and L-NAME injections.

CONCLUSIONS

Premature rat intestine is highly resistant to I/R injury, which may indicate that I/R alone, in the absence of other predisposing factors (eg, bacterial colonization) may not be sufficient in causing NEC. Nitric oxide does not have a protective role for immature and newborn intestines in I/R as in mature intestine. The high level of SODs of the immature and newborn intestine may play an important role in its high resistance to I/R injury.

Enteric glial cells. An upstream target for induction of necrotizing enterocolitis and Crohn's disease?

As a direct consequence of the sophisticated arrangement of its intrinsic neurons, the gastrointestinal tract is unique among peripheral organs, in its ability to mediate its own reflexes. Neurons of the enteric nervous system are intimately associated with enteric glial cells. These supporting cells do not resemble Schwann cells, the glial cell found in all other parts of the peripheral nervous system, but share many similarities with astrocytes of the central nervous system. Ablation of enteric glial cells in adult transgenic mice has demonstrated that these cells are essential to maintain the integrity of the small intestine. Acute loss of enteric glial cells induces massive pathological changes with similarities to necrotizing enterocolitis (NEC) and early Crohn's disease. These human conditions share some mechanistic similarities. Identification of enteric glial cell dysfunction/loss as sufficient to induce necrotic/inflammatory bowel disease may be important to understand the pathogenesis of both NEC and Crohn's disease.

Lactoferrin protects neonatal rats from gut-related systemic infection

Lactoferrin is a milk protein that reportedly protects infants from gut-related, systemic infection. Proof for this concept is limited and was addressed during in vivo and in vitro studies. Neonatal rats pretreated orally with recombinant human lactoferrin (rh-LF) had less bacteremia and lower disease severity scores (P < 0.001) after intestinal infection with Escherichia coli. Control animals had 1,000-fold more colony-forming units of E. coli per milliliter of blood than treated animals (P < 0.001). Liver cultures from control animals had a twofold increase in bacterial counts compared with cultures from rh-LF-treated pups (P < 0.02). Oral therapy with rh-LF + FeSO(4) did not alter the protective effect. In vitro studies confirmed that rh-LF interacted with the infecting bacterium and rat macrophages. An in vitro assay showed that rh-LF did not kill E. coli, but a combination of rh-LF + lysozyme was microbicidal. In vitro studies showed that rat macrophages released escalating amounts of nitric oxide and tumor necrosis factor-alpha when stimulated with increasing concentrations of rh-LF. The in vitro studies suggest that rh-LF may act with other "natural peptide antibiotics" or may prime macrophages to kill E. coli in vivo.

Necrotizing enterocolitis presenting in the Emergency Department: case report and review of differential considerations for vomiting in the neonate

Historically, most of the acute complications of prematurity have occurred in the neonatal intensive care unit, not in the Emergency Department (ED). It is becoming increasingly common, however, for premature infants to be discharged from the hospital before they have reached a postconceptual age of 40 weeks. Such infants remain at relatively increased risk for a variety of complications of prematurity and may present to the ED in their first month of life. To highlight its symptomatology and review its management, we present the case of an infant presenting back to the ED with coffee ground emesis and fulminant necrotizing enterocolitis.