Jamie Golden

Pathogenesis of neonatal necrotizing enterocolitis

AbstractAlthough necrotizing enterocolitis (NEC) is the most lethal gastrointestinal disease in the neonatal population, its pathogenesis is poorly understood. Risk factors include prematurity, bacterial colonization, and formula feeding. This review examines how mucosal injury permits opportunistic pathogens to breach the gut barrier and incite an inflammatory response that leads to sustained overproduction of mediators such as nitric oxide and its potent adduct, peroxynitrite. These mediators not only exacerbate the initial mucosal injury, but they also suppress the intestinal repair mechanisms, which further compromises the gut barrier and culminates in bacterial translocation, sepsis, and full-blown NEC.

Bile acids regulate intestinal cell proliferation by modulating EGFR and FXR signaling

Bile acids (BAs) are synthesized in the liver and secreted into the intestine. In the lumen, enteric bacteria metabolize BAs from conjugated, primary forms into more toxic unconjugated, secondary metabolites. Secondary BAs can be injurious to the intestine and may contribute to disease. The epidermal growth factor receptor (EGFR) and the nuclear farnesoid X receptor (FXR) are known to interact with BAs. In this study we examined the effects of BAs on intestinal epithelial cell proliferation and investigated the possible roles for EGFR and FXR in these effects. We report that taurine-conjugated cholic acid (TCA) induced proliferation, while its unconjugated secondary counterpart deoxycholic acid (DCA) inhibited proliferation. TCA stimulated phosphorylation of Src, EGFR, and ERK 1/2. Pharmacological blockade of any of these pathways or genetic ablation of EGFR abrogated TCA-stimulated proliferation. Interestingly, Src or EGFR inhibitors eliminated TCA-induced phosphorylation of both molecules, suggesting that their activation is interdependent. In contrast to TCA, DCA exposure diminished EGFR phosphorylation, and pharmacological or siRNA blockade of FXR abolished DCA-induced inhibition of proliferation. Taken together, these results suggest that TCA induces intestinal cell proliferation via Src, EGFR, and ERK activation. In contrast, DCA inhibits proliferation via an FXR-dependent mechanism that may include downstream inactivation of the EGFR/Src/ERK pathway. Since elevated secondary BA levels are the result of specific bacterial modification, this may provide a mechanism through which an altered microbiota contributes to normal or abnormal intestinal epithelial cell proliferation.

Reducing scheduled phlebotomy in stable pediatric patients with blunt liver or spleen injury.

BACKGROUND/PURPOSE Although consensus-based guidelines exist for managing pediatric liver/spleen injuries, optimal phlebotomy frequency is unknown. We hypothesize surgeons order more phlebotomy than necessary and propose a pathway with one blood draw, early ambulation and discharge, fewer ICU admissions, and physiology-driven interventions. METHODS Records of 120 children with solid organ injury from two hospital registries (2008-2012) were analyzed. We compared resource utilization between our current management and management if the proposed pathway were in place. Paired t-test was used for statistical analysis. RESULTS Sixty-one patients were included (35 spleen, 22 liver, 4 combined). Average age was 11.6 (±4.2) years, injury severity score 9 (±5), and median injury grade 3. 51% of children were admitted to the ICU. Average phlebotomy per patient was 5 (±2) and length-of-stay 4.3 (±1.5) days. Three patients became unstable and required transfusion. No patients required operation or angioembolization. Our pathway would decrease ICU admissions by 65% (p<0.001), blood draws by 70% (p<0.001), and length-of-stay by 37% (p<0.001), while identifying all patients requiring transfusion based on hemodynamic status. CONCLUSION Our data suggest that clinical parameters could identify patients requiring intervention and decrease resource utilization. This suggests that serial phlebotomy may be unnecessary, and the proposed pathway is worthy of prospective validation.

Limiting chest computed tomography in the evaluation of pediatric thoracic trauma.

BACKGROUND Computed tomography (CT) of the chest (chest CT) is overused in blunt pediatric thoracic trauma. Chest CT adds to the diagnosis of thoracic injury but rarely changes patient management. We sought to identify a subset of blunt pediatric trauma patients who would benefit from a screening chest CT based on their admission chest x-ray (CXR) findings. We hypothesize that limiting chest CT to patients with an abnormal mediastinal silhouette identifies intrathoracic vascular injuries not otherwise seen on CXR. METHODS All blunt trauma activations that underwent an admission CXR at our Level 1 pediatric trauma center from 2005 to 2013 were retrospectively reviewed. Patients who had a chest CT were evaluated for added diagnoses and change in management after CT. RESULTS An admission CXR was performed in 1,035 patients. One hundred thirty-nine patients had a CT, and the diagnosis of intra-thoracic injury was added in 42% of patients. Chest CT significantly increased the diagnosis of contusion or atelectasis (30.3% vs 60.4%; p < 0.05), pneumothorax (7.2% vs 18.7%; p < 0.05), and other fractures (4.3% vs 10.8%; p < 0.05) on CXR compared to chest CT. Chest CT changed the management of only 4 patients (2.9%). Two patients underwent further radiologic evaluation that was negative for injury, one had a chest tube placed for an occult pneumothorax before exploratory laparotomy, and one patient had a thoracotomy for repair of aortic injury. Chest CT for select patients with an abnormal mediastinal silhouette on CXR would have decreased CT scans by 80% yet still identified patients with an intrathoracic vascular injury. CONCLUSIONS The use of chest CT should be limited to the identification of intrathoracic vascular injuries in the setting of an abnormal mediastinal silhouette on CXR. LEVEL OF EVIDENCE Therapeutic study, level IV; diagnostic study, level III.

Heller Myotomy Is Superior to Balloon Dilatation or Botulinum Injection in Children with Achalasia: A Two-Center Review

INTRODUCTION Achalasia is an uncommon disorder in children. Currently, there is no consensus regarding the optimal treatment for achalasia. We investigate the effectiveness of symptom relief in patients who underwent endoscopic treatments versus Heller myotomy (HM). METHODS We conducted a retrospective review of all children (age 0-18 years) treated for achalasia at two pediatric hospitals from 2004 to 2014. Demographics, presenting symptoms, outcomes, and complications were analyzed. RESULTS Twenty-three patients (61% male) were identified with a mean age at diagnosis of 11.6 ± 5.0 years. About 47.8% of the cohort had no comorbidities. Common presenting symptoms included weight loss/failure to thrive (87.0%), emesis (69.6%), and dysphagia (69.6%). Mean time from symptom onset to diagnosis was 18 ± 18.9 months. Nine patients underwent laparoscopic HM as their primary treatment, whereas 14 received esophageal dilatation (ED) as their first-line therapy. Patients who underwent ED as their initial treatment were younger (9.92 versus 15.6 years, P = .047). Patients who underwent HM were more likely to attain symptom resolution compared to those managed with ED alone (P = .004). Of the 14 patients who underwent ED initially, 10 subsequently required HM due to persistent symptoms. None of the 4 patients who underwent ED alone achieved long-term symptom relief and, on the average, required an increased number of procedures compared to their HM counterparts (5.25 versus 2.47, P = .010). There was a trend toward increased intraoperative mucosal perforation in patients who underwent preoperative ED and botulinum injections. CONCLUSION Our data suggest that HM is superior to balloon dilatation or botulinum injection in children with achalasia. We conclude that HM should be recommended for newly diagnosed children with achalasia as a first-line therapy.

Admission hematocrit predicts the need for transfusion secondary to hemorrhage in pediatric blunt trauma patients.

BACKGROUND Pediatric trauma uses a substantial amount of resources. Quick and cost-effective measures that can be used to identify children with clinically relevant injuries are essential to resource allocation and optimization of patient care. Admission hematocrit is rapid and inexpensive, causes minimal harm, and can potentially aid in critical decision making. We hypothesize that admission hematocrit predicts the need for transfusion in pediatric blunt trauma patients. METHODS Records of trauma patients age 0 year to 17 years (2005–2013) who presented to a pediatric Level 1 trauma center were retrospectively reviewed. Data collected include demographics, computed tomographic scan findings, need for an intervention secondary to bleeding (blood transfusion, angioembolization, or operation), and admission hematocrit. RESULTS We found a significant decrease in admission hematocrit between patients requiring a transfusion and patients who did not (27% vs. 36%, p < 0.01). We evaluated a subset of patients who had an abdominal computed tomographic scan and found a significant decrease in admission hemocrit between those who required a transfusion for an intra-abdominal injury and those who did not (29% vs 37%, p < 0.01). In this subset, serial hematocrit values remained significantly lower in the patients requiring a transfusion up to 67 hours after admission (p = 0.04). A cutoff admission hematocrit of 35% or less has a sensitivity of 94% and a negative predictive value of 99.9% in identifying children who need a transfusion after blunt trauma. CONCLUSION An admission hematocrit of 35% or less provides a reliable screening test because of its low false negative rate and high specificity for identifying patients at an increased risk of bleeding after injury. Admission hematocrit could be widely implemented to identify patients who may need a transfusion with low expense and minimal harm for our pediatric patients and may be able to alter the entire course of their trauma resuscitation. LEVEL OF EVIDENCE Epidemiologic/prognostic study, level III.

Colonization with Escherichia coli EC 25 protects neonatal rats from necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a significant cause of morbidity and mortality in premature infants; yet its pathogenesis remains poorly understood. To evaluate the role of intestinal bacteria in protection against NEC, we assessed the ability of naturally occurring intestinal colonizer E. coli EC25 to influence composition of intestinal microbiota and NEC pathology in the neonatal rat model. Experimental NEC was induced in neonatal rats by formula feeding/hypoxia, and graded histologically. Bacterial populations were characterized by plating on blood agar, scoring colony classes, and identifying each class by sequencing 16S rDNA. Binding of bacteria to, and induction of apoptosis in IEC-6 enterocytes were examined by plating on blood agar and fluorescent staining for fragmented DNA. E. coli EC 25, which was originally isolated from healthy rats, efficiently colonized the intestine and protected from NEC following introduction to newborn rats with formula at 106 or 108 cfu. Protection did not depend significantly on EC25 inoculum size or load in the intestine, but positively correlated with the fraction of EC25 in the microbiome. Introduction of EC25 did not prevent colonization with other bacteria and did not significantly alter bacterial diversity. EC25 neither induced cultured enterocyte apoptosis, nor protected from apoptosis induced by an enteropathogenic strain of Cronobacter muytjensii. Our results show that E. coli EC25 is a commensal strain that efficiently colonizes the neonatal intestine and protects from NEC.

Lactobacillus murinus HF12 colonizes neonatal gut and protects rats from necrotizing enterocolitis

The use of lactobacilli in prevention of necrotizing enterocolitis (NEC) is hampered by insufficient knowledge about optimal species/strains and effects on intestinal bacterial populations. We therefore sought to identify lactobacilli naturally occurring in postnatal rats and examine their ability to colonize the neonatal intestine and protect from NEC. L. murinus, L. acidophilus, and L. johnsonii were found in 42, 20, and 1 out of 51 4-day old rats, respectively. Higher proportion of L. murinus in microbiota correlated with lower NEC scores. Inoculation with each of the three species during first feeding significantly augmented intestinal populations of lactobacilli four days later, indicating successful colonization. L. murinus, but not L. acidophilus or L. johnsonii, significantly protected against NEC. Thus, lactobacilli protect rats from NEC in a species- or strain-specific manner. Our results may help rationalizing probiotic therapy in NEC.

Routine contrast enema is not required for all infants prior to ostomy reversal: A 10-year single-center experience

INTRODUCTION The incidence of intestinal stricture is low for most conditions requiring a primary small bowel stoma in infants. Routine performance of contrast enemas (CE) prior to stoma closure adds cost and radiation exposure. We hypothesized that routine CE prior to ostomy reversal is not necessary in all infants, and sought to identify a subset of patients who may benefit from preoperative CE. METHODS Medical records of infants under age 1 (N=161) undergoing small bowel stoma reversal at a single institution between 2003 and 2013 were retrospectively reviewed. Students T-test was used to compare groups. RESULTS Contrast enemas were performed on 80% of all infants undergoing small bowel ostomy reversal during the study period. Infants with necrotizing enterocolitis (NEC) were more likely to have a CE than those with intestinal atresia (p=0.03) or those with all other diagnoses combined (p=0.03). Nine strictures were identified on CE. Of those, 8 (89%) were in patients with NEC, and only 4 were clinically significant and required operative resection. The overall relevant stricture rate was 2.5%. No patient that underwent ostomy takedown without CE had a stricture diagnosed intraoperatively or an unrecognized stricture that presented clinically after stoma takedown. CONCLUSIONS Routine CE is not required prior to small bowel ostomy reversal in infants. We recommend judicious use of enema studies in patients with NEC and high likelihood of stricture.

Liquid chromatography–mass spectroscopy as a tool in the rapid diagnosis of biliary atresia: a pilot study

INTRODUCTION Biliary atresia (BA) is a neonatal obstructive cholangiopathy requiring rapid intervention to prevent end-stage liver failure and death. Low bile acid levels in stool, detectable with high-performance liquid chromatography-mass spectroscopy, may reflect extrahepatic biliary obstruction in cholestasis. HYPOTHESIS Stool bile acid content can differentiate BA from non-BA forms of cholestasis. METHODS Stool samples from four healthy and nine cholestatic patients were collected following internal review board approval. Bile acids were extracted and separated on a 4000-Q-Trap HPLC-MS system. RESULTS Total bile acid content was highest in samples from healthy relative to cholestatic patients: 3354.01 ± 2102.56, 1476.27 ± 1361.07, and 34.29 ± 10.30 μM/mg of stool in healthy, total parenteral nutrition-associated cholestasis, and BA samples, respectively. Mean cholic acid and chenodeoxycholic acid concentrations in healthy samples (2017.5 ± 1413.6 and 876.83 ± 660.60 μM/mg) were higher than in TPN cholestatic samples (93.99±131.55 and 232.34 ± 293.41 μM/mg). The most dramatic reduction in cholic acid and chenodeoxycholic acid was observed in BA samples (0.65 ± 0.47 and 1.22 ± 0.80 μM/mg). CONCLUSION Bile acid content in stool is reduced in cholestatic patients relative to healthy patients with the most dramatic reduction observed in BA-patients.