Manometric recordings bring out post-stimulus refractory states in the anal canal in neonates.

Anorectal manometry is a diagnostic technique used to investigate the correct mechanical performance of the internal anal sphincter (IAS). By distending the rectal ampulla while recording changes in the luminal pressure, this method allows for characterizing the anorectal reflex. It can also provide, indirectly, information about the electrical activity of the IAS. In this study, seventeen neonates having 24-hour delayed passage of meconium or presenting distal intestinal obstruction symptoms underwent anorectal manometry to discard Hirschsprung's disease. All patients had normal anorectal reflex. The time delay between stimulation of the rectal ampulla and the relaxation of the anal canal was studied. The average period of the pressure fluctuations was 5.44 ± 0.13s. The overall duration of the relaxation time was 9.71 ± 0.21s. The maximum lag between the onset of the stimulus and the relaxation of the IAS was 2.90 s, and was achieved when the stimulus was applied following a local maximum of the pressure wave. The existence of a refractory period during the suprathreshold depolarization of smooth muscle cells can explain the evidence of a temporal delay between the stimulus and the mechanical response. In occasions, relaxation appeared first distally. This phenomenon can be explained by the arrangement and morphology of bipolar cells, which may evidence the anisotropic propagation of the mechanical activity. These data may contribute to depict the alterations in excitability underlying the relaxation reflex by means of manometric recording of the anal canal.

El índice de síntomas binomial para la evaluación de la asociación temporal entre síntomas cardiorespiratorios y reflujo gastroesofágico en neonatos / The binomial symptom index for the evaluation of temporal association between cardiorespiratory symptoms and gastroesophageal reflux in neonates

INTRODUCCIÓN: La evaluación de la asociación de síntomas entre el reflujo gastroesofágico y los eventos cardiorrespiratorios no está aún resuelta. Este artículo describe una aproximación conservadora para la decisión del tratamiento quirúrgico anti-reflujo mediante el análisis de la asociación de síntomas. MÉTODOS: Cuarenta y tres neonatos con síntomas cardiorrespiratorios potencialmente asociados al reflujo se sometieron a una monitorización cardiorrespiratoria y de pH-impedancia esofágica. Se consideraron tres índices, el índice de síntomas (IS), el índice de sensibilidad de síntomas (ISS) y la probabilidad de asociación de síntomas (PAS). Asimismo, se adoptó una estrategia conservadora para la aplicación de cirugía anti-reflujo, de manera que solo se consideró el tratamiento quirúrgico en aquellos pacientes con valor significativo en los tres índices. Se contrastaron retrospectivamente estos índices y el índice de síntomas binomial (ISB) frente a la decisión de cirugía anti-reflujo utilizando diferentes ventanas de asociación. RESULTADOS: Trece pacientes mostraron algún índice con valor significativo pero solo dos se sometieron al tratamiento quirúrgico. Tanto el IS como el ISS mostraron una tendencia creciente al aumentar el ancho de la ventana de asociación. El PAS sufrió fuertes variaciones aleatorias frente a pequeños cambios del enventanado. El ISB presentó el mejor resultado con la ventana de dos minutos (κ=0.78). CONCLUSIONES: La patología bajo estudio mejora con la madurez del individuo. Sin embargo, la severidad de los síntomas cardiorrespiratorios puede amenazar la vida del neonato y por lo tanto, en algunas ocasiones se deben considerar tratamientos invasivos para proteger la vida. El ISB proporciona una buena predicción de la combinación de valores positivos del IS, ISS y PAS, lo que puede ayudar a mejorar las decisiones clínicas. Sin embargo, son necesarios futuros estudios que prueben al ISB como un predictor óptimo de los eventos clínicos

INTRODUCTION: The evaluation of symptom association between gastroesophageal reflux and cardiorespiratory events in preterm infants remains unclear. This paper describes a conservative approach to decision-making of anti-reflux surgery through symptom association analysis. METHODS: Forty-three neonates with potentially reflux-related cardiorespiratory symptoms underwent synchronized esophageal impedance-pH and cardiorespiratory monitoring. Three indices were considered to evaluate symptom association, the symptom index (SI), the symptom sensitivity index (SSI) and the symptom association probability (SAP). A conservative strategy was adopted regarding the decision of anti-reflux surgery, and therefore, patients were scheduled for laparoscopic Nissen fundoplication if the three indices showed a positive assessment of symptom association. Retrospectively, these indices and the binomial symptom index (BSI) were contrasted against the decision of anti-reflux surgery using different windows of association. RESULTS: Thirteen patients showed positive symptom association but only two underwent anti-reflux surgery. The SI and the SSI showed an increasing trend with the width of the window of association. The SAP was affected randomly by slightly altering the windowing parameters. The BSI showed the best performance with the two-minute window (κ=0.78). CONCLUSIONS: The pathology under study is known to improve with maturity. However, the severity of cardiorespiratory symptoms may threaten the neonate's life and therefore, on some occasions, invasive treatments must be considered to protect life. The BSI provides a good prediction of a combination of positive SI, SSI and SAP, which may improve clinical decisions. However, further clinical studies are required to prove the BSI as an optimal predictor of clinical outcomes

[The binomial symptom index for the evaluation of temporal association between cardiorespiratory symptoms and gastroesophageal reflux in neonates]. / El índice de síntomas binomial para la evaluación de la asociación temporal entre síntomas cardiorrespiratorios y reflujo gastroesofágico en neonatos.

INTRODUCTION: The evaluation of symptom association between gastroesophageal reflux and cardiorespiratory events in preterm infants remains unclear. This paper describes a conservative approach to decision-making of anti-reflux surgery through symptom association analysis. METHODS: Forty-three neonates with potentially reflux-related cardiorespiratory symptoms underwent synchronized esophageal impedance-pH and cardiorespiratory monitoring. Three indices were considered to evaluate symptom association, the symptom index (SI), the symptom sensitivity index (SSI) and the symptom association probability (SAP). A conservative strategy was adopted regarding the decision of anti-reflux surgery, and therefore, patients were scheduled for laparoscopic Nissen fundoplication if the three indices showed a positive assessment of symptom association. Retrospectively, these indices and the binomial symptom index (BSI) were contrasted against the decision of anti-reflux surgery using different windows of association. RESULTS: Thirteen patients showed positive symptom association but only two underwent anti-reflux surgery. The SI and the SSI showed an increasing trend with the width of the window of association. The SAP was affected randomly by slightly altering the windowing parameters. The BSI showed the best performance with the two-minute window (κ =0.78) CONCLUSIONS: The pathology under study is known to improve with maturity. However, the severity of cardiorespiratory symptoms may threaten the neonate's life and therefore, in some occasions, invasive treatments must be considered to protect life. The BSI provides a good prediction of a combination of positive SI, SSI and SAP, which may improve clinical decisions. However, further clinical studies are required to prove the BSI as an optimal predictor of clinical outcomes.

Resultados del descenso endorrectal transanal en la enfermedad de Hirschsprun / Results of transanal endorrectal descent in Hirschprung’s disease

OBJETIVO: Presentar nuestra experiencia en el tratamiento de pacientes con enfermedad de Hirschsprung (EH) intervenidos mediante descenso endorrectal transanal (DET). MÉTODOS: Estudio retrospectivo de los DET realizados. Correlacionamos, fundamentalmente, longitud del segmento agangliónico, con complicaciones, necesidad de colostomía y vía de abordaje. RESULTADOS: Entre 2003 y 2012 hemos realizado 73 DET (57 varones), 78,6% diagnosticados en el periodo neonatal. La longitud agangliónica objetivada en el enema se correspondió con los hallazgos quirúrgicos en un 68,9% de los casos; esta correspondencia fue mayor en las formas cortas que en las largas o pancolónicas (80,9 vs. 44%; p < 0,001). Cuatro pacientes precisaron colostomía preoperatoria. La edad media al descenso fue de 6,3 meses (rango 4,5-33,7). El 64,4% eran formas cortas. El abordaje abdominal fue necesario en 10 pacientes (13,6%), 9 de ellos aganglionismos largos o pancolónicos. El 10,9% (8 pacientes) ha presentado enterocolitis postoperatoria, sin relación con la longitud agangliónica ni con la existencia de displasia residual. La suboclusión por bridas se presentó en el 19,2% de las formas largas o pancolónicas. Actualmente, de los pacientes valorables, 5 tienen hábito estreñido y 12 presentan escapes ocasionales. CONCLUSIONES: El DET es la cirugía de elección para pacientes con EH. La mayoría pueden manejarse con «nursing» preoperatorio, sin colostomía. Las pruebas diagnósticas de elección son la manometría y la biopsia rectal por succión. No hemos encontrado correlación entre la existencia de enterocolitis y la longitud del segmento agangliónico, aunque hemos observado una reducción drástica de las enterocolitis postoperatorias, desde la introducción de modificaciones técnicas, como la sonda rectal posquirúrgica y la sección posterior del manguito muscular

OBJECTIVE: To present our experience of patients with Hirschsprung disease (HD) operated by transanal endorrectal descent (TED). METHODS: A retrospective study performed of TEDs. We correlate fundamentally the aganglionic segment length with: Complications, need for colostomy and surgical approach. RESULTS: Between 2003 and 2012 we performed 73 TED (57 men), 78.6% diagnosed in the neonatal period. The aganglionic segment length evidenced in the enema was correlated with surgical findings in 68.9% of cases, being higher in the short forms than in the long segments (80.9 vs. 44%, P<.001). Four patients required preoperative colostomy. The mean age of surgery was 6.3 months (4.5 to 33.7). Short forms represented 64.4% of cases. The abdominal approach was necessary in 10 patients, 9 of these were long/total colonic aganglionic segment. Postoperative enterocolitis presented in 10,9% (9 patients), with no relation with the length of aganglionic or the existence of residual dysplasia. Obstructions occurred in 19.2% of the long form or pancolonic forms. Currently, of the evaluable patients, 5 present constipationand 12 present occasional leakage. CONCLUSIONS: TED is the surgery of choice for patients with HD. The majority can be handled by preoperative «nursing» without colostomy. The diagnostic tests of choice are manometry with suction biopsy. No significant correlation was found between enterocolitis and length of aganglionic segment, although we observed a drastic reduction of postoperative enterocolitis, since the introduction of technical changes, such as the use of postoperative rectal tubes and the posterior section of the cuff muscles

Results of transanal endorrectal descent in Hirschprung's disease.

OBJECTIVE: To present our experience of patients with Hirschsprung disease (HD) operated by transanal endorrectal descent (TED). METHODS: A retrospective study performed of TEDs. We correlate fundamentally the aganglionic segment length with: Complications, need for colostomy and surgical approach. RESULTS: Between 2003 and 2012 we performed 73 TED (57 men), 78.6% diagnosed in the neonatal period. The aganglionic segment length evidenced in the enema was correlated with surgical findings in 68.9% of cases, being higher in the short forms than in the long segments (80.9 vs. 44%, P<.001). Four patients required preoperative colostomy. The mean age of surgery was 6.3 months (4.5 to 33.7). Short forms represented 64.4% of cases. The abdominal approach was necessary in 10 patients, 9 of these were long/total colonic aganglionic segment. Postoperative enterocolitis presented in 10,9% (9 patients), with no relation with the length of aganglionic or the existence of residual dysplasia. Obstructions occurred in 19.2% of the long form or pancolonic forms. Currently, of the evaluable patients, 5 present constipationand 12 present occasional leakage. CONCLUSIONS: TED is the surgery of choice for patients with HD. The majority can be handled by preoperative «nursing¼ without colostomy. The diagnostic tests of choice are manometry with suction biopsy. No significant correlation was found between enterocolitis and length of aganglionic segment, although we observed a drastic reduction of postoperative enterocolitis, since the introduction of technical changes, such as the use of postoperative rectal tubes and the posterior section of the cuff muscles.

Software for symptom association analysis in pediatric gastroesophageal reflux disease.

Gastroesophageal reflux (GER) disease is a serious complication of the upper gastrointestinal tract. Cardiorespiratory symptoms such as apnea, oxygen desaturation and bradycardia may be related to GER. Thus, the recommended diagnostic methodology in pediatric patients requires 24-h synchronized esophageal and cardiorespiratory monitoring. However, there is no computer tool available for this purpose and therefore, researchers and physicians are forced to seek for customized solutions. This paper presents an open source computer program for the analysis of symptom association. It allows a convenient visualization of the biological signals and implements the three main metrics for symptom association, that is, the symptom index, the symptom sensitivity index and the symptom association probability. This software represents a flexible solution and will facilitate caregivers an easy assessment of the existence of temporal association between GER and cardiorespiratory episodes. This would ideally reduce inappropriate medical and surgical treatments and would provide an early diagnosis of the medical condition.

Involvement of SOX10 in the pathogenesis of Hirschsprung disease: report of a truncating mutation in an isolated patient.

SOX10 protein is a key transcription factor during neural crest development. Mutations in SOX10 are associated with several neurocristopathies such as Waardenburg syndrome type IV (WS4), a congenital disorder characterized by the association of hearing loss, pigmentary abnormalities, and absence of ganglion cells in the myenteric and submucosal plexus of the gastrointestinal tract, also known as aganglionic megacolon or Hirschsprung disease (HSCR). Several mutations at this locus are known to cause a high percentage of WS4 cases, but no SOX10 mutations had been ever reported associated to isolated HSCR patient. Therefore, nonsyndromic HSCR was initially thought not to be associated to mutations at this particular locus. In the present study, we describe the evaluation of the SOX10 gene in a series of 196 isolated HSCR cases, the largest patient series evaluated so far, and report a truncating c.153-155del mutation. This is the first time that a SOX10 mutation is detected in an isolated HSCR patient, which completely changes the scenario for the implications of SOX10 mutations in human disease, giving us a new tool for genetic counseling.

New roles of EDNRB and EDN3 in the pathogenesis of Hirschsprung disease.

PURPOSE: Hirschsprung disease is characterized by the absence of intramural ganglion cells in the myenteric and submucosal plexuses within distal intestine, because of a fail in the enteric nervous system formations process. Endothelin-3-endothelin receptor B signaling pathway is known to play an essential role in this process. The aim of this study was to evaluate the implication of the EDN3 and EDNRB genes in a series of patients with Hirschsprung disease from Spain and determinate their mutational spectrum. METHODS: We performed the mutational screening of both genes in 196 patients with Hirschsprung disease using denaturing high-performance liquid chromatography technology. A case-control study using TaqMan Technology was also carried out to evaluate some common polymorphisms and haplotypes as susceptibility factors for Hirschsprung disease. RESULTS: Besides several novel mutations in both genes, we found a truncating mutation in an alternative isoform of EDNRB. Interestingly, we obtained an overrepresentation of a specific EDN3 haplotype in cases versus controls. CONCLUSIONS: Our results suggest that the isoform EDNRB Delta 3 might be playing an essential role in the formation of enteric nervous system. In addition, based on the haplotype distribution, EDN3 might be considered as a common susceptibility gene for sporadic Hirschsprung disease in a low-penetrance fashion.

A novel study of copy number variations in Hirschsprung disease using the multiple ligation-dependent probe amplification (MLPA) technique.

BACKGROUND: Hirschsprung disease (HSCR) is a congenital malformation of the hindgut produced by a disruption in neural crest cell migration during embryonic development. HSCR has a complex genetic etiology and mutations in several genes, mainly the RET proto-oncogene, have been related to the disease. There is a clear predominance of missense/nonsense mutations in these genes whereas copy number variations (CNVs) have been seldom described, probably due to the limitations of conventional techniques usually employed for mutational analysis. METHODS: In this study we have aimed to analyze the presence of CNVs in some HSCR genes (RET, EDN3, GDNF and ZFHX1B) using the Multiple Ligation-dependent Probe Amplification (MLPA) approach. RESULTS: Two alterations in the MLPA profiles of RET and EDN3 were detected, but a detailed inspection showed that the decrease in the corresponding dosages were due to point mutations affecting the hybridization probes regions. CONCLUSION: Our results indicate that CNVs of the gene coding regions analyzed here are not a common molecular cause of Hirschsprung disease. However, further studies are required to determine the presence of CNVs affecting non-coding regulatory regions, as well as other candidate genes.

Endosonography of the anal canal: findings in children.

PURPOSE: The aim of this study was to determine the endosonographic anatomy in children to define normal age-related differences in sphincter morphology and measurements. METHODS: One hundred ten consecutive children (76 males and 34 females; mean age, 3.94 years; range, 1.10-15.09) with endoanal ultrasonography were studied. The thickness of the anal canal of the internal and external anal sphincter of each child was registered and correlated with the age. RESULTS: At the high level, the puborectalis muscles were clearly visualized, with a median thickness of 4.73 mm, and the internal anal sphincters were observed, with a mean thickness of 1.21 mm. At the mid level, both the internal and external anal sphincters were visualized, as well. The mean internal anal sphincter thickness was 1.23 mm and the median thickness of the external anal sphincter was 4.47 mm. At the lower level, the median external anal sphincter thickness was 5.39 mm. There was no significant correlation between the thickness of the internal and external sphincters and sex. The puborectalis and the external anal sphincter thickness showed a highly significant positive correlation with age. There was no significant correlation between the internal sphincter thickness and age. CONCLUSIONS: The endosonographic morphology of children is similar to that of adults, although the structures in children less than 5 years of age are difficult to differentiate. We detected a significant increase in the thickness of the external anal sphincter as patients grow older, but not in the internal anal sphincter.

Is the RET proto-oncogene involved in the pathogenesis of intestinal neuronal dysplasia type B?

Hirschsprung disease (HSCR) is defined by the absence of intramural ganglia of Meissner and Auerbach along variable lengths of the gastrointestinal tract. Intestinal neuronal dysplasia (IND) type B is characterized by the malformation of the parasympathetic submucous plexus of the gut. A connection appears to exist between these two enteric nervous system abnormalities. Due to the major role played by the RET proto-oncogene in HSCR, we sought to determine whether this gene was also related to INDB. dHPLC techniques were employed to screen the RET coding region in 23 patients presenting with INDB and 30 patients with a combined HSCR+INDB phenotype. In addition, eight RET single nucleotide polymorphisms (SNPs) were strategically selected and genotyped by TaqMan technology. The distribution of SNPs and haplotypes was compared among the different groups of patients (INDB, HSCR+INDB, HSCR) and the controls. We found several RET mutations in our patients and some differences in the distribution of the RET SNPs among the groups of study. Our results suggest an involvement of RET in the pathogenesis of intestinal INDB, although by different molecular mechanisms than those leading to HSCR. Further investigation is warranted to elucidate these precise mechanisms and to clarify the genetic nature of INDB.

Polymorphisms in the genes encoding the 4 RET ligands, GDNF, NTN, ARTN, PSPN, and susceptibility to Hirschsprung disease.

PURPOSE: Hirschsprung disease (HSCR) is a developmental disorder caused by a failure of neural crest cells to migrate, proliferate, and/or differentiate during the enteric nervous system development. It presents a multifactorial, nonmendelian pattern of inheritance, with several genes playing some role in its pathogenesis. Its major susceptibility gene is the RET protooncogene, which encodes a receptor tyrosine kinase activating several key signaling pathways in the enteric nervous system development. Given the pivotal role of RET in HSCR, the genes encoding their ligands (GDNF, NRTN, ARTN, and PSPN) are also good candidates for the disease. METHODS: We have performed a case-control study using Taqman technology to evaluate 10 polymorphisms within these genes, as well as haplotypes comprising them, as susceptibility factors for HSCR. RESULTS: No differences were found in the allelic frequencies of the variants or in the haplotype distribution between patients and controls. In addition, no particular association was detected of the variants/haplotypes to any demographic/clinical parameters within the group of patients. CONCLUSION: These data would be consistent with the lack of association between these polymorphisms and HSCR, although they do not permit to completely discard a possible role of other variants within these genes in the disease. Moreover, because the gene-by-gene approach does not take into account the polygenic nature of HSCR disease, it would be interesting to investigate sets of variants in many other different susceptibility loci described for HSCR, which may permit to consider possible interactions among susceptibility genes.

NTF-3, a gene involved in the enteric nervous system development, as a candidate gene for Hirschsprung disease.

Hirschsprung disease (HSCR) is a congenital disorder caused by a failure of neural crest cells to migrate, proliferate, and/or differentiate during the enteric nervous system (ENS) development. The requirement of the NTF-3/TrkC signaling for the proper development of the ENS, together with the evidences presented by animal models, led us to investigate the involvement of NTF-3 gene in HSCR. We performed both a mutational screening of NTF-3 and a complete evaluation of 3 polymorphisms as genetic susceptibility factors for HSCR. We identified a novel sequence variant, G76R, present in 2 different patients and absent in controls. We postulate that this variation could generate a lack of mature functional NTF-3 proteins in neural crest cell precursors; thus, altering the NTF-3/TrkC signaling pathway and influencing in the adequate ENS development. Although these results do not provide complete assurance of the involvement of this gene in HSCR, given the polygenic nature of the disease and its etiology, investigation of the genes encoding protein members of the signaling pathways governing the ENS development could provide new key findings in the elucidation of this complex disease.

A complex additive model of inheritance for Hirschsprung disease is supported by both RET mutations and predisposing RET haplotypes.

PURPOSE: The RET proto-oncogene is considered to be the major susceptibility gene involved in Hirschsprung disease. Traditional RET germline mutations account for a small subset of Hirschsprung disease patients, but several studies have shown that there is a specific haplotype of RET associated with the sporadic forms of Hirschsprung disease. We have investigated for RET germline mutations and analyzed the RET haplotypic distribution in carriers versus noncarriers of RET germline mutations. METHODS: We have screened the coding region of RET in 106 Spanish Hirschsprung disease patients using dHPLC technology. Statistical comparisons of the distribution of RET haplotypes between sporadic patients with and without a RET germline mutation were performed. RESULTS: Nine novel germline mutations and one previously described were identified. A significant over-transmission of the "Hirschsprung disease haplotype" was detected when comparing transmitted versus nontransmitted alleles in the group of Hirschsprung disease triads without mutation. However, no distortion of the transmission of alleles was found in the group of mutated families. CONCLUSIONS: These results would be concordant with a complex additive model of inheritance. The whole findings seem to suggest that low-penetrance mutations would be necessary but not sufficient and the additional presence of the "Hirschsprung disease haplotype" could contribute to the manifestation of the disease.

Twenty-four-hour esophageal impedance-pH monitoring in healthy preterm neonates: rate and characteristics of acid, weakly acidic, and weakly alkaline gastroesophageal reflux.

OBJECTIVE: Gastroesophageal reflux is a physiologic process and is considered pathologic (gastroesophageal reflux disease) when it causes symptoms or results in complications. It is common in preterm infants and occurs in healthy neonates. Twenty-four-hour pH monitoring commonly is used in children for diagnosis of gastroesophageal reflux disease, and abnormal reflux is considered with detection of increased esophageal acid exposure. However, in neonates, relatively few gastroesophageal reflux episodes cause esophageal acidification to pH < 4. Premature infants receive frequent feeds, which can induce a weaker acid secretory response than that observed in older infants and adults. As a consequence, gastric pH may be > 4 for prolonged periods, and reflux of gastric contents might be less acidic or even alkaline. Esophageal impedance monitoring can detect weakly acidic and even alkaline gastroesophageal reflux. The role of weakly acidic reflux in the pathophysiology of gastroesophageal reflux disease in preterm infants is not clear. To date, studies that have used impedance-pH in neonates assessed the association between nonacid reflux and cardiorespiratory symptoms, but no impedance data from healthy preterm neonates have been available to determine whether those symptomatic neonates had an increased number of weakly acidic reflux episodes or increased reactivity to a physiologic number of reflux events. Our aim with this study was to provide impedance-pH values for acid, weakly acidic, and weakly alkaline reflux from healthy preterm neonates. METHODS: Esophageal impedance was recorded for 24 hours in 21 asymptomatic preterm neonates by replacing the conventional feeding tube with a specially designed feeding tube that included 9 impedance electrodes (8 French). All neonates were asymptomatic, with spontaneous breathing. Reflux monitoring was performed after comprehensive explanation and on receipt of written parental consent. Esophageal and gastric pH were monitored using a separate parallel pediatric catheter (6 French). According to the corresponding pH change, impedance-detected reflux was classified as acid, weakly acidic, and weakly alkaline. For each infant, the total number of reflux events, the acid exposure and bolus exposure times at 2 cm above the respiratory inversion point, and average proximal extent of reflux were calculated. RESULTS: Twenty-six preterm neonates were recruited into this study. A preliminary analysis was performed, and tracings were classified according to their quality and the presence of technical artifacts (spontaneous pH and impedance drifts, esophageal probe migration, and dysfunction of 1 or more impedance channels). Five studies were excluded because of 1 or more technical artifacts; a total of 21 neonates represent the final cohort included. At birth, the infants had a median postmenstrual age of 32 weeks, and the measurements were performed at a median age of 12 days. The total recording time was 23.7 +/- 2 hours. Gastric pH was higher than 4 during 69.3 +/- 20.4% of the recording time. The median number of reflux events in 24 hours was 71, 25.4% (range: 0%-53.1%) of which were acid, 72.9% (range: 45.3%-98.0%) were weakly acidic, and 0% (range: 0%-8.1%) were weakly alkaline. Compared with fasting periods, feeding periods tended to be associated with a higher number of total reflux events per hour. The acidity of reflux, however, was significantly different: during fasting, the number of acid reflux episodes per hour was higher, whereas during feeding, the number of weakly acidic reflux episodes was increased. Most reflux events were only liquid, whereas gas was present either mixed with liquid or pure only in 7.7% of all reflux episodes detected. The proximal esophageal segments were reached in 90% of reflux episodes. Reflux-related acid exposure (pH drops associated with impedance-detected reflux) was 1.66% (range: 0%-6.43%), whereas total acid exposure (associated and not associated with reflux detected by impedance) was 5.59% (range: 0.04%-20.69%). There was no relationship between the number or acidity of reflux events and anthropometric parameters such as weight and gestational age. CONCLUSIONS: We present the first study using 24-hour impedance-pH recordings in asymptomatic premature neonates. Previous studies that used pH-metry suggested that neonatal cardiorespiratory symptoms could be related to acid gastroesophageal reflux. However, pH-metry could not detect accurately weakly acidic or nonacid reflux. Our healthy premature neonates had approximately 70 reflux events in 24 hours, 25% of which were acid, 73% were weakly acidic, and 2% were weakly alkaline. The number of reflux events per hour (2-3 per hour) was slightly lower than that described in premature neonates with cardiorespiratory events (4 per hour). We confirmed that weakly acidic reflux is more prevalent than acid reflux, particularly so during the feeding periods. In contrast, similar to healthy adults, weakly alkaline reflux was very rare. We confirmed findings from previous studies in which most reflux events were pure liquid during both fasting and during postprandial periods and gas reflux was very rare. As in neonates with cardiorespiratory symptoms, the majority of reflux events in asymptomatic preterms reached the proximal esophagus or pharynx, and there were no differences between acid and weakly acidic reflux. The lack of differences between asymptomatic and diseased infants contravenes the hypothesis for macro- or microaspiration but does not exclude hypersensitivity to reflux as a cause for respiratory symptoms. The acid exposure that was related to reflux events and detected by impedance was significantly lower than the total acid exposure during 24 hours. Increased acid exposure could be attributable to pH-only reflux events or, less frequently, to slow drifts of pH from baselines at approximately 5 to values < 4. These changes were not accompanied by a typical impedance pattern of reflux but by slow drifts in impedance in 1 or 2 channels. Our findings confirm the need for the use of impedance together with pH-metry for diagnosis of all gastroesophageal reflux events. The relationship between gastroesophageal reflux and cardiorespiratory events in neonates and older infants has been studied extensively. The current evidence for such a relationship is controversial. This study provides values of impedance-pH monitoring for acid, weakly acidic, and weakly alkaline reflux from healthy preterm neonates that can be used for comparison when evaluating gastroesophageal reflux in preterm infants with a cardiorespiratory disease.

A founding locus within the RET proto-oncogene may account for a large proportion of apparently sporadic Hirschsprung disease and a subset of cases of sporadic medullary thyroid carcinoma.

Hirschsprung disease (HSCR) is a common congenital disorder characterized by aganglionosis of the gut. The seemingly unrelated multiple endocrine neoplasia type 2 (MEN 2) is an autosomal dominant disorder characterized by medullary thyroid carcinoma (MTC), pheochromocytoma, and hyperparathyroidism. Yet, germline mutations in the RET proto-oncogene are associated with both MEN 2 and HSCR. In the former, gain-of-function mutations in a limited set of codons is found, whereas, in the latter, loss-of-function mutations are found. However, germline RET mutation is associated with only 3% of a population-based series of isolated HSCR, and little is known about susceptibility to sporadic MTC. We have found previously that specific haplotypes comprising RET coding single-nucleotide polymorphisms (SNPs) comprising exon 2 SNP A45A were strongly associated with HSCR, whereas haplotypes associated with exon 14 SNP S836S were associated with MTC. In this study, we describe three novel intron 1 SNPs, and, together with the coding SNP haplotypes, the data suggest the presence of distinct ancestral haplotypes for HSCR and sporadic MTC in linkage disequilibrium with a putative founding susceptibility locus/loci. The data are consistent with the presence of a very ancient, low-penetrance founder locus approximately 20-30 kb upstream of SNP A45A, but the failure of the SNPs to span the locus presents challenges in modeling mode of transmission or ancestry. We postulate that this founding locus is germane to both isolated HSCR and MTC but also that different mutations in this locus would predispose to one or the other.