Necrotizing enterocolitis

Necrotizing enterocolitis and the placenta - a key etiological link

AIM

Necrotizing enterocolitis (NEC) is the most common and severe acquired acute neonatal surgical condition, associated with premature neonates. Antenatal factors (e.g. vascular insufficiency and antenatal infections) may be important factors in "priming" the inflammatory cascade, thus predisposing to the disease. This study explores the role of placental pathology in predisposing to NEC pathogenesis.

METHODS

5338 placentas of high risk pregnancies were evaluated for placental insufficiency, infarction, and evidence of antenatal infection. Placentas of 72 premature infants developing surgical NEC (2007-2011) were identified as a separate study group and pathological placental features compared with unaffected infants.

RESULTS

Placentas of 72 of the 134 infants with surgically treated NEC (>grade 2 Bells) were available for pathologic evaluation (the remainder having been referred from other delivery units). Placentas of surgical NEC cases had significantly more evidence of noteworthy vascular pathology (placental infarcts) than high risk cases [n=38 (54.5%) versus n=1122 (21%); P<0.01]. Evidence of placental infection/chorioamnionitis or villitis plus evidence of foetal inflammatory response was present in surgical NEC infants versus unaffected infants [n=22 (31.8%) versus n=647 (12%); P<0.01], suggesting a possible pathogenic role.

CONCLUSION

This study suggests that exposure to antenatal placental infection may contribute to pathogenesis of NEC by modifying foetal vascular response and warrants further study.

Comparison of the efficacy of serum amyloid A, C-reactive protein, and procalcitonin in the diagnosis and follow-up of necrotizing enterocolitis in premature infants

PURPOSE

The aim of this study was to compare the efficacy of serum amyloid A (SAA) with that of C-reactive protein (CRP), and procalcitonin (PCT) in diagnosis and follow-up of necrotizing enterocolitis (NEC) in preterm infants.

METHODS

A total of 152 infants were enrolled into this observational study. The infants were classified into 3 groups: group 1 (58 infants with NEC and sepsis), group 2 (54 infants with only sepsis), and group 3 (40 infants with neither sepsis nor NEC, or control group). The data including whole blood count, CRP, PCT, SAA, and cultures that were obtained at diagnosis (0 hour), at 24 and 48 hours, and at 7 and 10 days were evaluated.

RESULTS

A total of 58 infants had a diagnosis of NEC. Mean CRP (7.4 ± 5.2 mg/dL) and SAA (46.2 ± 41.3 mg/dL) values of infants in group 1 at 0 hour were significantly higher than those in groups 2 and 3. Although the area under the curve of CRP was higher at 0 hour in infants with NEC, there were no significant differences between groups with respect to the areas under the curve of SAA, CRP, and PCT at all measurement times. Levels of SAA decreased earlier than CRP and PCT in the follow-up of NEC (mean SAA levels were 45.8 ± 45.2, 21.9 ± 16.6, 10.1 ± 8.3, and 7.9 ± 5.1 mg/dL at evaluation times, respectively). Levels of CRP and SAA of infants with NEC stages II and III were significantly higher than those with only sepsis and/or NEC stage I.

CONCLUSIONS

Serum amyloid A, CRP, and PCT all are accurate and reliable markers in diagnosis of NEC, in addition to clinical and radiographic findings. Higher CRP and SAA levels might indicate advanced stage of NEC. Serial measurements of SAA, CRP, and PCT, either alone or in combination, can be used safely in the diagnosis and follow-up of NEC.

Decision-making in surgical neonatal necrotizing enterocolitis

AIM

To know whether laboratory or clinical parameters can predict disease progression, need for laparotomy in patients managed with peritoneal drain and mortality in surgical neonatal necrotizing enterocolitis patients.

MATERIALS AND METHODS

The study was retrospectively carried out on 27 neonates over a period of one and a half year. All neonates who had surgical neonatal necrotizing enterocolitis in the form of bowel perforation, positive paracentesis, abdominal wall erythema and abdominal lump were included. Patients with Bell's stage I and those developing enterocolitis after surgery were excluded. The patients were evaluated with parameters, namely, clinical, laboratory and radiological. These included age and stage at presentation, primary symptom/sign at presentation with laboratory parameters of blood counts, pH, base deficit, platelet counts, electrolytes and random blood sugar levels. A comparison was done between survivors and nonsurvivors, patients with primary peritoneal drainage versus those requiring laparotomy after drain, Bell' stage II versus III patients and operated versus nonoperated patients. Statistical significance was observed in the above mentioned comparisons.

RESULTS

There were 22 male and 5 females patients with mean birth weight of 1.85 kg. Age at presentation ranged from 2 to 19 days, mean 9.25 days. Mortality was 37% (10/27). Majority of the stage II patients presented with feed intolerance and abdominal distension. The neonates with severe disease had abdominal distension with wall erythema. Sixty percent of the patients had shock at the time of admission. In the comparison of peritoneal drain only and patients with peritoneal drain followed by laparotomy patients, it was observed that neonates who were acidotic and had higher base deficit had more chances of requirement of laparotomy. They also had progressive fall in platelets counts. There was no difference in the birth weight, gestational age, total counts, serum electrolytes, blood sugar and other measured parameters; thus, these carry negligible predictive value to judge deteriorating neonate. In the remaining of the comparison, patients not presenting with shock were more likely to survive.

CONCLUSION

In the present study, neonate with persistently low pH, higher base deficit and presentation with shock predicted need for laparotomy in drain managed patients as well as chances of survival.

Diet-dependent mucosal colonization and interleukin-1beta responses in preterm pigs susceptible to necrotizing enterocolitis

OBJECTIVES

Intestinal colonization challenges the neonatal innate immune system, especially in newborns with an immature immune response lacking the supportive bioactive components from mother's milk. Accordingly, formula-fed preterm pigs frequently show bacterial overgrowth, mucosal atrophy, and gut lesions reflecting necrotizing enterocolitis (NEC) within the first days after birth. We hypothesized that NEC development is related to a diet-dependent bacterial adherence and a subsequent proinflammatory cytokine response in the gut mucosa immediately after introduction of enteral food.

MATERIALS AND METHODS

Premature piglets (92% gestation) received 2 to 3 days of total parenteral nutrition followed by 0, 8, or 17 hours of enteral formula or sow's colostrum feeding.

RESULTS

Following 8 hours, but not 17 hours, of colostrum feeding, a reduced number of intestinal samples with adherent bacteria (both Gram-negative and Gram-positive bacteria) was counted compared with 0 or 8 hours of formula feeding. Besides a more dense colonization, formula feeding leads to higher intestinal interleukin-1beta (IL-1beta) levels and more NEC-like lesions from 8 hours onward. The load of adherent bacteria was especially high in NEC lesions. Toll-like receptor 4 was detected in enteroendocrine, neuronal, and smooth muscle cells, potentially mediating the increase in IL-1beta levels by Gram-negative bacteria.

CONCLUSIONS

Formula feeding facilitates bacterial adherence and the development of a proinflammatory state of the intestine, which may be among the key factors that predispose formula-fed preterm neonates to NEC.

Valor preditivo da distensão de alças intestinais em radiografias no prognóstico de enterocolite necrosante

OBJETIVO: Avaliar o valor prognóstico da distensão de alças intestinais observada em radiografias na evolução e mortalidade de neonatos com enterocolite necrosante. MATERIAIS E MÉTODOS: Nas radiografias de abdome de 53 pacientes obtidas no momento da suspeita diagnóstica de enterocolite necrosante, foi realizada a medida do diâmetro da alça mais distendida (AD), assim como a distância entre a borda superior da primeira vértebra lombar e a borda inferior da segunda (L1-L2), a distância entre as bordas laterais dos pedículos da primeira vértebra lombar (L1), e foram estabelecidas as associações entre AD/L1-L2 e AD/L1. Esta medida foi considerada como possível determinante de potenciais complicações, intervenção cirúrgica e mortalidade. RESULTADOS: Os pacientes que necessitaram de tratamento cirúrgico, aqueles que tiveram complicações durante a evolução e aqueles que morreram da doença tiveram a relação entre AD e AD/L1-L2 maiores (p < 0,05). Os valores de AD/L1 e a localização da alça mais distendida não foram diferentes nos grupos com evolução desfavorável. CONCLUSÃO: Distensão de alça intestinal detectada em radiografias de abdome realizadas na admissão sugerem pior prognóstico em enterocolite necrosante. Outrossim, medidas do diâmetro da alça mais distendida nessas radiografias são um método simples e reprodutível que oferece informações diagnósticas e prognósticas.

Clostridium difficile and Clostridium perfringens species detected in infant faecal microbiota using 16S rRNA targeted probes

Clostridium perfringens and Clostridium difficile are pathogenic clostridia potentially associated with gastrointestinal infections and allergy in infants. To enable the molecular detection and quantification of these species in the infant gut, two 16S rRNA oligonucleotide probes were developed: Cdif198 for C. difficile and Cperf191 for C. perfringens. We defined the probes in silico using the RDP sequence database. The probes were then validated using FISH combined with flow cytometry and a collection of target and non-target strains, and faecal samples inoculated with dilutions of C. difficile and C. perfringens strains. These new probes were used to assess the composition of the intestinal microbiota of 33 infants of 1.5 to 18.5 months of age, associated with a panel of 8 probes targeting the predominant faecal bacterial groups of humans. The probes designed allowed detection and quantification of the relative proportions of C. difficile (0.5+/-1.0%) and C. perfringens (2.1+/-2.3%) in the microbiota of infants.

Laboratory parameters predictive of developing necrotizing enterocolitis in infants born before 33 weeks of gestation

PURPOSE

The aim of this study was to identify laboratory findings predictive of necrotizing enterocolitis (NEC).

METHODS

Prospective follow-up of 140 infants of less than 33 weeks of gestation. Twenty-six infants developed NEC (grades I to III, criteria of Bell et al [Ann Surg 1978;187:1-7]) (NEC group). For each, 2 birth-weight, gestational age- and postnatal age-matched controls were selected (control group). Blood counts, glucose and electrolyte levels, C-reactive protein, and acid-base balance 3 days, 2 days, and 1 day before and at the onset of NEC and at corresponding ages from the controls were recorded.

RESULTS

Metabolic acidosis occurred, the platelet levels decreased, and the blood glucose increased on successive days in the infants with grade NEC II-III. At the onset of NEC, the infants had significantly lower platelet and higher blood glucose levels compared with controls. More than half of infants with intestinal perforation had leukocyte levels above 30 x 10(9)/L and pH less than 7.25, and their mean blood glucose levels increased to more than 1.5 mmol/L in 24 hours. The remaining parameters were not useful.

CONCLUSION

A persistent metabolic acidosis, decreasing platelet, and increasing blood glucose level on several successive days might predict a developing NEC, and leukocyte values above 30 x 10(9)/L, pH less than 7.25, and a blood glucose rise by 1.5 mmol/L or more within 24 hours predict NEC with intestinal perforation. Such findings should alert the physician to look for signs of NEC in a preterm infant.

Evidence for clostridial implication in necrotizing enterocolitis through bacterial fermentation in a gnotobiotic quail model

Despite extensive research, the pathogenesis of neonatal necrotizing enterocolitis (NEC) remains elusive. The aim of our work was to investigate the role of bacterial strains involved in NEC in gnotobiotic quails as experimental model. Six groups of germ-free quails that were fed a lactose diet were associated with Klebsiella pneumoniae, Clostridium perfringens, C. difficile, C. paraputrificum, or C. butyricum (two strains). Implantation level, incidence of cecal lesions, production of short-chain fatty acids, and histologic lesions of the cecal wall were investigated. Whatever the strain, the implantation level was high (10(9) UFC/g). Neither K. pneumoniae nor C. difficile induced any cecal lesions. In contrast, the four other clostridial strains led to cecal NEC-like lesions with a variable occurrence: four of 12 quails for C. perfringens, eight of 12 quails for C. paraputrificum, and the same highest value, nine of 12 quails and eight of 10 quails for both C. butyricum strains. Gross aspects of the lesions may be linked to the short-chain fatty acid profiles and/or concentrations: thickening of the cecal wall (C. butyricum and C. perfringens) with high proportion of butyric acid, hemorrhages (C. paraputrificum) with high proportion of iso-butyric acid, and presence of other iso-acids. In addition, C. butyricum was characterized by pneumatosis, linked to a high gas production. Microscopic aspects confirmed the presence of edemas and intramucosa hemorrhages. Clostridia species, whose role is controversial, seem to be strongly implicated in NEC through excessive production of butyric acid as a result of colonic lactose fermentation. These results call for anaerobe detection in feces of infants who have NEC.

Distinctive distribution of pathogens associated with peritonitis in neonates with focal intestinal perforation compared with necrotizing enterocolitis

OBJECTIVE

Candida and coagulase-negative staphylococci are emerging pathogens associated with focal intestinal perforation (FIP) and necrotizing enterocolitis (NEC) in neonates. The objective of this study was to determine whether there are significant differences in the predominant pathogens in culture-positive cases of peritonitis associated with FIP compared with NEC in neonates.

METHODS

A retrospective cross-sectional study was conducted of neonates with peritoneal culture-positive peritonitis associated with FIP or NEC over a 12-year study period (1989-2000). Cases with peritonitis were identified from a microbiology database. NEC was defined by radiologic evidence of pneumatosis intestinalis or portal venous gas or by pathology reports or surgical operative notes describing large areas of transmural bowel necrosis. FIP was defined as a <1-cm intestinal perforation surrounded by otherwise normal tissue in the absence of NEC.

RESULTS

Thirty-six cases of FIP were compared with 80 cases of NEC. Birth weight and gestational age were significantly lower in infants with FIP compared with NEC. Age at intestinal perforation and case fatality rates were similar between FIP and NEC. There were striking differences in the distribution of predominant pathogens associated with peritonitis in NEC and FIP cases. Enterobacteriaceae were present in 60 (75%) of 80 NEC cases compared with 9 (25%) of 36 FIP cases. In contrast, Candida species were found in 16 (44%) of 36 FIP cases compared with 12 (15%) of 80 NEC cases, and coagulase-negative staphylococci were present in 18 (50%) of 36 FIP cases versus 11 (14%) of 80 NEC cases. There were no significant differences between FIP and NEC cases for the presence of Enterococcus species (28% vs 23%) or anaerobes (3% vs 6%). Stratified analysis for birth weight <1200 g found similar significant differences in the predominant pathogens for FIP (n = 29) and NEC (n = 38). Results from peritoneal fluid cultures resulted in changes in antimicrobial therapy in 46 (40%) of 116 cases.

CONCLUSIONS

Candida species and coagulase-negative staphylococci were the predominant pathogens in FIP peritonitis in contrast to Enterobacteriaceae in NEC peritonitis. A peritoneal fluid culture should be obtained in all neonates with intestinal perforation, regardless of cause, because it may help to direct the choice of the most effective antimicrobial.

Pathophysiology and current management of necrotizing enterocolitis

Necrotizing enterocolitis continues to be a common and life-threatening gastrointestinal emergency in the low birth weight infant. Prematurity, ischemia, enteral feeding, and infectious disease have been identified as common risk factors, however the exact cause of NEC other than prematurity is yet to be identified. Good assessment skills by the nurse are imperative, because clinical signs of NEC can be both subtle and catastrophic. Frequent radiographs are essential for the diagnosis of NEC and ongoing assessment of neonates diagnosed with NEC. Radiographs including an abdominal flat plate examination and a left lateral decubitus film to evaluate for free air should be obtained every 6-8 hours in the neonates with Stages II and III NEC.

Trefoil factor family peptide 3 prevents the development and promotes healing of ischemia-reperfusion injury in weanling rats

BACKGROUND/PURPOSE

Although the pathogenesis of necrotizing enterocolitis (NEC) is not completely defined, ischemia appears to be one of the most important causative factors. Trefoil factor family peptide 3 (TFF3) is a peptide normally expressed in the small bowel and colon and is involved in the maintenance and repair of mucosal integrity. The authors hypothesized that monomeric (TFF3 Ser57) and dimeric (TFF3 Cys57) recombinant TFF3 may prevent the development and accelerate healing of intestinal ischemia-reperfusion injury in weanling rats.

METHODS

Intestinal injury was induced in 18-day-old rats by occlusion of the superior mesenteric vessels for 60 minutes. To examine the protective effect, rats were given 3 microg/g of TFF3 Ser57 or TFF3 Cys57 by subcutaneous or enteral administration 30 minutes before the vascular occlusion. To examine the healing effect, rats were given 3 microg/g of TFF3 Ser57 or TFF3 Cys57 by subcutaneous or enteral administration 60 minutes after the beginning of reperfusion. Samples from small bowel and colon were collected for morphometric analysis after 3 hours of reperfusion. Mucosal damage was assessed by the Chiu score.

RESULTS

Both forms of TFF3 reduced the amount of damage when administered before the ischemia. Administration of TFF3 Ser57 and TFF3 Cys57 after the beginning of reperfusion significantly increased the villous height and decreased the Chiu score in the small intestine and colon.

CONCLUSIONS

TFF3 Ser57 monomer and TFF3 Cys57 dimer prevent the development and promote healing of ischemia-reperfusion injury in weanling rats. There are no differences between the routes of administration of TFF3.

Early intestinal bacterial colonization and necrotizing enterocolitis in premature infants: the putative role of Clostridium

Necrotizing enterocolitis (NEC) is among the most severe conditions that can affect preterm infants. Although the etiology of NEC remains unknown, initial bacterial colonization could play a pivotal role in the development of NEC. To further explore the putative relationship between pathogen microorganisms and NEC, we conducted a prospective case-control study in 12 preterm infants with a new approach based on molecular techniques. Over an inclusion period of 24 mo, 12 neonates of <34 wk gestational age admitted to the neonatal unit were enrolled. The group included three cases of NEC, and nine control infants without evidence of NEC who were matched for gestational age and birth weight. Stool samples were collected at weekly intervals from all infants. PCR and temporal temperature gradient gel electrophoresis of 16S ribosomal DNA were used to detect the establishment of bacterial communities in the digestive tract. A salient feature of the bacteriological pattern was observed only in the three infants who later developed NEC: A band corresponding to the Clostridium perfringens subgroup could be detected in early samples, before diagnosis. There was no evidence for this specific band in any of the nine controls. To our knowledge, the current report is the first to demonstrate that the use of molecular techniques based on the study of bacterial 16S rRNA genes allowed the recognition of C. perfringens species in the first 2 wk of life of three infants who later displayed symptoms of NEC. A significant temporal relationship was thus established between early colonization by Clostridium and the later development of NEC. Compared with conventional bacteriological culturing methods, the use of this new molecular approach to analyze the gastrointestinal ecosystem should therefore allow a more complete and rapid assessment of intestinal flora. Although the current data do not constitute definitive proof that the identified bacterial species was a causative agent in the development of NEC, they outline the promise of this new technique based on molecular biology, and suggest that large-scale studies on a much wider population at high risk for NEC may be warranted.

Surgical treatments of infants with necrotizing enterocolitis

With the improvements in neonatal intensive care, necrotizing enterocolitis (NEC) has become the most common gastrointestinal emergency amongst infants in neonatal intensive care units. The incidence of NEC varies between 1 and 8% of neonatal intensive care unit admissions and the disease has a mortality rate between 20 and 40%. There are a number of surgical options available to the paediatric surgeon depending on the clinical condition of the infant and the extent of the disease. However owing to a paucity of prospective data in this field and a lack of randomized controlled trials there is little consensus as to which is the most appropriate. Primary peritoneal drainage has become very popular in North America and Europe for the treatment of perforated NEC in very low-birthweight infants. It is a useful manoeuvre in the resuscitation of critically ill infants and in some of these infants, further operation may be avoided completely by inserting a peritoneal drain. Others however remain too unwell to undergo laparotomy and may die. Two randomized controlled trials are currently underway to determine the real benefit of peritoneal drainage. Laparotomy in very small neonates has become safer with improvements in anaesthesia and intensive care management. Resection and primary anastomosis has been proposed as a valid treatment modality in neonates with both focal and multifocal disease. The advantage of resection and primary anastomosis over stoma formation is still controversial. Different surgical techniques such as diverting jejunostomy or 'clip and drop' have been described to deal with extensive disease and avoid massive small bowel resection. Prospective studies and randomized controlled trials are needed to define the best operative treatment for neonates with severe NEC.

Treatment and prevention of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the most common serious, acquired gastrointestinal disorder in the newborn infant. Although many variables are associated with development of NEC, only prematurity has been consistently identified in case-controlled studies. Traditionally, the diving seal reflex has been invoked as the mechanism responsible for ischaemic injury and necrosis. Intestinal ischaemia is likely to be the final common pathway in NEC; however, it is due to the release of vasoconstricting substances, such as platelet activating factor, rather than perinatal asphyxia. Bacteria and/or bacterial toxins are likely to have a key role in the pathogenesis of NEC by fostering production of inflammatory mediators. The role of feeding practices in the pathogenesis of NEC remains controversial. Treatment of infants with NEC generally includes a regimen of bowel rest, gastric decompression, systemic antibiotics and parenteral nutrition. Infants with perforation are generally operated upon; however, there has been recent interest in primary peritoneal drainage as an alternative. Prevention of NEC still remains elusive. Avoidance of preterm birth, use of antenatal steroids and breast-milk feeding are practices that offer the greatest potential benefits. Use of any other strategy should await further trials.

Tolerance of a sterile isotonic electrolyte solution containing select recombinant growth factors in neonates recovering from necrotizing enterocolitis

OBJECTIVE

To assess the tolerance of a sterile isotonic electrolyte solution containing select recombinant growth factors enterally administered in neonates who were NPO because of necrotizing enterocolitis (NEC).

STUDY DESIGN

A phase I trial was accomplished among 30 neonates. Patients received 5, 10, or 20 mL enterally of the study solution/kg/day divided into every 3-hour dosing, for 3 days prior to when feedings of milk were to resume. The occurrence of emesis, gastric residuals, diarrhea, bloody stools, abdominal distention, skin rashes and death were sought.

RESULTS

Gestational ages ranged from 25.2 to 41.1 weeks. A total of 16 neonates had Stage IA NEC, six Stage IB, and eight Stage IIA. The solution was well tolerated in all 30; none developed diarrhea, guaiac positive or bloody stools, or abdominal distention. Administration of the solution was not prematurely discontinued in any infant. Two neonates died secondary to late-onset sepsis remote from the study period.

CONCLUSIONS

Enteral administration of a sterile isotonic electrolyte solution containing select recombinant growth factors was well tolerated by neonates with NEC.

Outcome of Perforated Necrotizing Enterocolitis in the Very Low-Birth Weight Neonate May be Independent of the Type of Surgical Treatment

Perforated necrotizing enterocolitis (NEC) in the low-birth weight infant is now one of the most common surgical problems encountered in contemporary neonatal intensive care units. However, morbidity and mortality from NEC remain high, and the optimal surgical management of these infants remains controversial. Currently few data exist comparing the factors influencing outcome in very low-birth weight infants with perforated NEC treated by either local drainage or exploration. We hypothesize that survival of very low-birth weight neonates with perforated NEC may be more dependent on clinical status than on treatment modality. We present our experience treating a large cohort of infants weighing less than 1000 g with perforated NEC. A retrospective cohort study describes our experience with perforated NEC in very low-birth weight infants in a Level III neonatal intensive care unit. Between January 1991 and May 1998 a total of 70 newborn infants weighing less than 1000 g were evaluated and managed for perforated NEC. Comorbid factors were identified and calculated for each infant. Primary treatment was either local drainage or laparotomy. Statistical analysis was performed by Student's t test and multiple logistic regression. A multiple logistic regression model examined factors (comorbidities, number of comorbidities, and mode intervention) influencing outcome. A Kaplan-Meier survival analysis comparing survival versus number of comorbidities was performed. Twenty-two infants with an average weight of 679 g were treated by local drainage. Forty-eight infants with an average weight of 756 g were treated with exploratory laparotomy. Infants treated by local drainage had a higher cumulative number of comorbid factors (5.2 ± 0.50 vs 3.7 ± 0.29; P < 0.05) than those managed by operative exploration. Fourteen infants (63%) initially undergoing local drainage for perforated NEC survived. Of the 48 infants 36 operated on survived (75%). No single factor or combination of any comorbid factors was predictive of outcome. The total number of comorbidities for each neonate did reach statistical significance ( P < 0.05). A greater likelihood of death was associated with a higher number of comorbidities. Survival with four or fewer comorbidities was 84 per cent, whereas survival with greater than six comorbidities was 30 per cent. The mean number of comorbidities was greater for drainage than for surgery, and for the same number of comorbidities the probability of survival tended to be greater for those treated with drainage than for those undergoing surgery. Multiple logistic regression analysis identified the total number of comorbidities as affecting outcome rather than treatment choice. This suggests therefore that selection of therapeutic options for the patient requires evaluating all factors that may impact survival rather than applying a single treatment strategy for all patients.

Molecular mechanisms contributing to necrotizing enterocolitis

OBJECTIVE

To examine the cellular mechanisms involved in the pathogenesis of necrotizing enterocolitis (NEC).

SUMMARY BACKGROUND DATA

Necrotizing enterocolitis is a major cause of death and complications in neonates; the cellular mechanisms responsible for NEC are unknown. The inducible form of cyclooxygenase (i.e., COX-2) is activated by the transcription factor nuclear factor (NF)-kappaB and is thought to play a role in inflammation.

METHODS

Segments of perforated and adjacent uninvolved small intestine from neonates with NEC were analyzed for COX-2 expression by immunohistochemistry. NEC was induced in weanling (18 days old) rats by occlusion of superior mesenteric vessels for 1 hour and intraluminal injection of platelet activating factor (50 micro/kg). Small intestine was harvested for protein extraction. Western immunoblot was performed to determine expression of COX-2. Gel shift assays were performed to assess NF-kappaB binding activity.

RESULTS

Immunohistochemical analysis showed increased COX-2 protein expression in the perforated intestinal sections of all 36 neonates but not in adjacent normal intestine. Increased expression of COX-2 protein and NF-kappaB binding activity was noted in the small intestine of weanling rats at 0 and 3 hours after induction of NEC.

CONCLUSIONS

Increased COX-2 expression was identified in all neonatal intestinal segments resected for perforated NEC. In addition, a coordinate induction of COX-2 expression and NF-kappaB binding was noted in a rodent model of NEC. These findings suggest that the COX-2/NF-kappaB pathway may play a role in the pathogenesis of NEC. Therapeutic agents that target this pathway may prove useful in the treatment or possible prevention of NEC.

The clinical significance of thrombocytopenia in neonates with necrotizing enterocolitis

PURPOSE

The aim of this study was to evaluate the clinical significance of low platelet count in the surgical management of neonates with necrotizing enterocolitis (NEC).

METHODS

The clinical course of 58 consecutive neonates with advanced NEC (Bell's stages II or III) treated in the authors' hospital between 1995 and 1998 was reviewed. NEC in neonates who required operation was classified as isolated, multifocal, or pan-intestinal. Severe thrombocytopenia was defined as platelet count less than 100 x 10(9)/L. Rapid fall in platelet count was defined as fall greater than 150 x 10(9)/L within 24 hours to a level less than 100 x 10(9)/L.

RESULTS

Median birth weight was 1,564 g (range, 550 to 4,270) and gestational age was 31 weeks (range 23 to 41). Twenty-two neonates (38%) were below 1,000 g. Age at the onset of the disease was 13 days (range, 1 to 62). NEC was treated medically in 7 neonates (12%). Indications for operation included pneumoperitoneum in 23 neonates (45%), clinical deterioration in 19 (37%), and intestinal obstruction in 9 (18%). The nadir platelet count (lowest level during the course of disease) was lower in patients with stage III disease than in patients with stage II disease (P <.05). The greater the extent of the disease, the lower the platelet count (P =.012). The nadir platelet count was lower in infants who died than in survivors (P <.05). None of the patients with platelet count greater than 100 x 10(9)/L died. In predicting intestinal gangrene, severe thrombocytopenia has a sensitivity of 69%, specificity of 60%, and positive predictive value of 89%; rapid fall in platelet count has a sensitivity of 32%, specificity of 89%, and positive predictive value of 92%.

CONCLUSIONS

(1) A platelet count less than 100 x 10(9)/L or a rapid fall in platelet count represent poor prognostic factors. (2) Monitoring the platelet count during the course of NEC is useful; however, it cannot be used in isolation to predict the extent of the disease or survival rate.

Necrotizing enterocolitis and hematopoietic cytokines

The names of the hematopoietic cytokines are misleading because in addition to their effects on bone marrow and bone marrow-derived cells, they have many diverse effects, including effects on the gastrointestinal tract. These effects may be directly mediated by interaction with specific receptors on gastrointestinal epithelial cells, or they may result from their effects on circulating or bowel wall leukocytes and the cytokines these cells produce. As might be expected of factors largely defined by their effects on inflammatory cells, the hematopoietic cytokines are intimately involved in the processes of bowel injury. Further investigations are needed to define the role of hematopoietic cytokines in the human neonate's balance between local gastrointestinal host defense and bowel wall injury. This could lead to effective strategies for the treatment and prevention of NEC.

Inflammation in the developing human intestine: A possible pathophysiologic contribution to necrotizing enterocolitis

Necrotizing enterocolitis (NEC), a major cause of morbidity and mortality in premature infants, occurs after the introduction of oral feedings in conjunction with initial bacterial colonization of the gut and is hypothesized to be due to an immature (inappropriate) enterocyte response to bacterial stimuli. To test this hypothesis, we compared the enterocyte IL-8 response to inflammatory stimuli [lipopolysaccharide (LPS) and IL-1beta] in immature vs. mature human small intestine. Initial in vitro studies comparing confluent Caco-2 cells, a model for mature human enterocytes, with a primary human fetal intestinal cell line (H4 cells) demonstrated that after inflammatory stimulation fetal cells secreted more IL-8 (LPS, 8-fold; IL-1beta, 20-fold) than Caco-2 cells. IL-8 mRNA activity in fetal compared to Caco-2 cells was proportionately increased by the same magnitude with both stimuli. To validate the in vitro observations, small intestinal organ cultures from fetuses vs. older children were exposed to LPS and IL-1beta. Again in human organ cultures from fetuses compared to older children, IL-8 secretion was greater (LPS, 2.5-fold; IL-1beta, 200-fold) and mRNA activity after stimulation was comparably higher, suggesting that increased transcription of the IL-8 gene may account for the excessive response. Using immunohistochemical staining to identify the cellular source of IL-8, activity was noted predominantly in villous and crypt epithelium but also in a few immunoresponsive lymphoid cells. The observation that immature human enterocytes react with excessive pro-inflammatory cytokine production after inflammatory stimulation may help in part explain why prematures exposed to initial colonizing bacteria develop necrotizing enterocolitis.

Carboxyl ester lipase activity in milk prevents fat-derived intestinal injury in neonatal mice

Carboxyl ester lipase (bile salt-stimulated lipase) is a pancreatic enzyme capable of hydrolyzing esters of cholesterol and fat-soluble vitamins. It also efficiently digests triglycerides (TG) into free fatty acids and glycerol and is abundant in the milk of humans and several other species. We used the mouse as a model to test the hypothesis that milk-derived carboxyl ester lipase (CEL) digests milk TG and that without its activity milk lipids and their digestion intermediates can disrupt the intestinal epithelium of neonates. CEL protein and enzymatic activity were shown to be abundant in mouse milk. After 24-h administration of the CEL-specific inhibitor, WAY-121,751-5, the small intestines of treated and control neonates were analyzed histologically for signs of fat malabsorption and injury to their villus epithelium. In vehicle-fed controls, TG were digested and absorbed in the duodenum and jejunum, whereas, in inhibitor-fed littermates, large intracellular neutral lipid droplets accumulated in enterocytes of the ileum, resulting in damage to the villus epithelium. Similar results were observed in neonates nursed by CEL knockout females compared with heterozygous controls. The results suggest that lack of CEL activity causes incomplete digestion of milk fat and lipid accumulation by enterocytes in the ileum of neonatal mice.

Post-treatment Dopexamine Infusions Partially Reverse Reductions in Cranial Mesenteric Blood Flow and Mucosal Oxygenation Induced by Hypoxia in Newborn Piglets

A severe hypoxic insult is known to induce dramatic reductions in newborn intestinal blood flow and is, thus, considered a vector for the development of neonatal intestinal ischemic diseases. Dopexamine (DPX) is a novel synthetic agent that has potent B2-adrenoceptor and dopaminergic activity, the clinical effects of which include an increase in cardiac output and in mesenteric blood flow. Having previously shown that infusion of DPX before hypoxia (HYP) mitigated the reduction in newborn mesenteric blood flow, we sought to define its efficacy when given after an established hypoxic insult. Ultrasonic transit time blood flow probes were placed around the ascending aorta and cranial mesenteric artery of anesthetized, mechanically ventilated 0 to 2-day-old piglets. Small bowel mucosal oxygenation was observed with a tissue oxygen monitoring system. After stabilization, animals were subjected to one of the following: HYP (FIO2 = 0.12) for 60 minutes (n = 12); DPX (5 μg/kg/min) infusion begun 10 minutes after induction of HYP/DPX (n = 11). Almost no alterations in any of the monitored variables were shown in a group (n = 5) of similarly instrumented, untreated animals. In contrast, although both hypoxic piglet groups experienced significant (P < 0.05, analysis of variance) declines from baseline cardiac output, mesenteric blood flow, and mucosal oxygenation, each of these deleterious effects was significantly (P < 0.05) blunted in the DPX-treated animals. During periods of systemic hypoxemia, the reductions in neonatal mesenteric blood flow and oxygenation can be somewhat blunted by DPX. As such, this agent may prove of clinical benefit when an infant is threatened by a hypoxic episode.