Smooth muscle cell hypertrophy versus hyperplasia in infantile hypertrophic pyloric stenosis

Diagnostic Accuracy of Acid-Base Status in Infants with Hypertrophic Pyloric Stenosis

Background: Hypertrophic pyloric stenosis is a condition in newborns in which the hypertrophic pyloric muscle causes gastric obstructive symptoms of progressive vomiting leading to hypochloremic hypokalemic metabolic alkalosis. The main aim of the research was to assess whether, based on the acid-base status, we can distinguish newborns who vomit due to pylorostenosis, compared with newborns who vomit for other unspecific reasons. Methods: The electronic records of patients in the hospital information system treated under the diagnosis Q40.0 (Congenital hypertrophic pyloric stenosis) (n = 69/included in the study = 53) in the period from 1 January 2014 to 1 January 2022 were reviewed retrospectively. For the purposes of the control group, the electronic records of patients treated in the emergency department with a diagnosis of R11.0 (Nausea and vomiting) (n = 53) without an established cause were randomly reviewed. In addition to the main aim, other research outcomes were to determine differences between groups in the following variables: duration of symptoms, family history, birth (preterm, term, post-term), birth weight, weight during examination, difference between birth weight and weight during an examination, type of vomiting, the thickness of the muscle wall and its length, and to calculate whether there is a correlation between the thickness and length of the pylorus muscle and the duration of vomiting in relation to variables from acid-base status. Results: In relation to the variables of interest between the groups, statistically significant differences were observed in the duration of symptoms (Mdn 4 vs. 2 days, p = 0.002), weight at examination (Mean 3880 vs. 4439 g, p = 0.001), difference in weight between birth and examination (Mean 374 vs. 1010 g, p < 0.0001), and type of vomiting (explosive 45 vs. 22, p = 0.023). In the acid-base status between the groups, a statistically significant difference was recorded for pH (Mdn 7.457 vs. 7.422, p < 0.0001), bicarbonate (Mdn 25 vs. 23 mmol/L, p = 0.000), total carbon dioxide (Mdn 25 vs. 24 mmol/L, p = 0.011), base excess (Mdn 0.8 vs. −1.3 mmol/L, p = 0.000), potassium (Mdn 5 vs. 5.3 mmol/L, p = 0.006), ionized calcium (Mdn 1.28 vs. 1.31 mmol/L, p = 0.011), and glucose (Mdn 4.5 vs. 4.9 mmol/L, p = 0.007). Regardless of the group, the correlations between the duration of vomiting (r = 0.316, p = 0.021 vs. r = 0.148, p = 0.290) and the thickness (r = 0.190, p = 0.172) and length (r = 0.142, p = 0.311) of the pylorus muscle in relation to pH did not exist or were weak. Conclusions: In a world where radiological methods are not equally available everywhere, with promising acid-base indicators, prospective multicenter studies and meta-analyses must be pursued in the future in order not to miss the possible much greater diagnostic potential of acid-base status.

Laparoscopic versus open pyloromyotomies: Outcomes and disparities in pyloric stenosis

PURPOSE

Pyloromyotomy for hypertrophic pyloric stenosis (HPS) is one of the most common non-elective operations performed in the neonatal period. This project aims to explore outcomes of pyloromyotomy and compare differences between laparoscopic versus open pyloromyotomies in newborns diagnosed with HPS.

METHODS

The Nationwide Readmissions Database (NRD) from 2010 to 2014 was queried to identify patients diagnosed with HPS that underwent repair.

RESULTS

In total, 30,915 children (18% female) underwent pyloromyotomy for HPS. Median length of stay for index admission was 2 days. A total of 212 (0.7%) patients required a redo pyloromyotomy. 127 (60%) were performed during index admission. Readmission rate at 30 days was 3% and 5% at one year, and 22% presented to a different hospital. The most common indications for readmission were feeding intolerance (24%), dehydration (10%), and malnutrition (10%). Patients from low-income households were more likely to present with malnutrition and weight loss (9% vs 4%, p<0.001) and had higher readmission rates (8% vs 4%, p<0.001). Laparoscopic pyloromyotomies accounted for 10% (n = 2951) of cases. Those undergoing laparoscopy were less likely to have electrolyte disturbances (41% vs 54%, p<0.001) or weight loss (2% vs 11%, p<0.001) on admission. The rate of open conversion was 1%. Intraoperative perforation was not more common in laparoscopic than open cases. Open pyloromyotomies had higher 30-day readmission rates and more surgical site infections.

CONCLUSION

Complications from pyloromyotomies are rare. Although infrequent, the incidence of incomplete pyloromyotomy is higher than previously reported and more common with open approaches. Newborns from low-income households are more likely to present with advanced symptoms and have disproportionately higher rates of readmission.

LEVEL OF EVIDENCE

Level III TYPE OF STUDY: Treatment Study, retrospective.

Protocol: A systematic review and meta-analysis of the role of fetal and infantile environmental exposure in etiopathogenesis of infantile hypertrophic pyloric stenosis

Infantile hypertrophic pyloric stenosis (IHPS) is one of the hallmark pediatric surgical diseases. However, its etiology remains incompletely understood. By systematically reviewing the literature, we aim to clarify the effect of the effect of occupational and environmental factors and role of nitric oxide (NO) metabolism in the etiopathogenesis of IHPS. The systematic review is drafted with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis statement (PRISMA) and the Meta-analysis of Observational Studies in Epidemiology (MOOSE). Systematic literature search will be performed for the period 2000 (Jan) to 2020 (Dec) in the databases: MEDLINE, EMBASE, PubMed. The systematic search will cover the literature in English and Turkish language and will be limited to studies on human subjects. Four investigators will independently search the databases (MEDLINE, EMBASE, PubMed) according to the defined search strategy. The full-text of the selected articles will be screened independently by four reviewers, against the inclusion criteria. Descriptive data will be extracted from each study regarding: study details, methods, participants, outcomes and calculations of association for potential further statistical analysis. If meta-analysis could not be undertaken, systematic approach to analyzing the findings of included multiple studies will be described. Heterogeneity will be assessed by quantifying the inconsistency across studies using I2 statistic. Statistical analysis will be performed using Comprehensive Meta-Analysis Version 3.0 software. The p values lower than 0.05 will be considered statistically significant for all analyses.

Pyloric stenosis: an enigma more than a century after the first successful treatment

Despite hypertrophic pyloric stenosis (HPS) being one of the most frequently treated pediatric surgical conditions, its etiology remains incompletely understood. We review the diagnosis and treatment of this condition with an emphasis on the evolution of surgical techniques that led to laparoscopic pyloromyotomy, the most frequently performed technique for HPS today. In addition, we review key developments in the understanding of HPS etiology and treatment, including the postulated etiology of work-induced hypertrophy of the pylorus, its association with prokinetic macrolide antibiotics, and the emerging role of atropine sulfate as a medical treatment for HPS or a rescue treatment for incomplete myotomy.

Bioengineering functional human sphincteric and non-sphincteric gastrointestinal smooth muscle constructs

Digestion and motility of luminal content through the gastrointestinal (GI) tract are achieved by cooperation between distinct cell types. Much of the 3 dimensional (3D) in vitro modeling used to study the GI physiology and disease focus solely on epithelial cells and not smooth muscle cells (SMCs). SMCs of the gut function either to propel and mix luminal contents (phasic; non-sphincteric) or to act as barriers to prevent the movement of luminal materials (tonic; sphincteric). Motility disorders including pyloric stenosis and chronic intestinal pseudoobstruction (CIPO) affect sphincteric and non-sphincteric SMCs, respectively. Bioengineering offers a useful tool to develop functional GI tissue mimics that possess similar characteristics to native tissue. The objective of this study was to bioengineer 3D human pyloric sphincter and small intestinal (SI) constructs in vitro that recapitulate the contractile phenotypes of sphincteric and non-sphincteric human GI SMCs. Bioengineered 3D human pylorus and circular SI SMC constructs were developed and displayed a contractile phenotype. Constructs composed of human pylorus SMCs displayed tonic SMC characteristics, including generation of basal tone, at higher levels than SI SMC constructs which is similar to what is seen in native tissue. Both constructs contracted in response to potassium chloride (KCl) and acetylcholine (ACh) and relaxed in response to vasoactive intestinal peptide (VIP). These studies provide the first bioengineered human pylorus constructs that maintain a sphincteric phenotype. These bioengineered constructs provide appropriate models to study motility disorders of the gut or replacement tissues for various GI organs.

Voltage dependent potassium channel remodeling in murine intestinal smooth muscle hypertrophy induced by partial obstruction

Partial obstruction of the small intestine causes obvious hypertrophy of smooth muscle cells and motility disorder in the bowel proximate to the obstruction. To identify electric remodeling of hypertrophic smooth muscles in partially obstructed murine small intestine, the patch-clamp and intracellular microelectrode recording methods were used to identify the possible electric remodeling and Western blot, immunofluorescence and immunoprecipitation were utilized to examine the channel protein expression and phosphorylation level changes in this research. After 14 days of obstruction, partial obstruction caused obvious smooth muscle hypertrophy in the proximally located intestine. The slow waves of intestinal smooth muscles in the dilated region were significantly suppressed, their amplitude and frequency were reduced, whilst the resting membrane potentials were depolarized compared with normal and sham animals. The current density of voltage dependent potassium channel (K_V) was significantly decreased in the hypertrophic smooth muscle cells and the voltage sensitivity of K_V activation was altered. The sensitivity of K_V currents (IK_V) to TEA, a nonselective potassium channel blocker, increased significantly, but the sensitivity of IKv to 4-AP, a K_V blocker, stays the same. The protein levels of K_V4.3 and K_V2.2 were up-regulated in the hypertrophic smooth muscle cell membrane. The serine and threonine phosphorylation levels of K_V4.3 and K_V2.2 were significantly increased in the hypertrophic smooth muscle cells. Thus this study represents the first identification of K_V channel remodeling in murine small intestinal smooth muscle hypertrophy induced by partial obstruction. The enhanced phosphorylations of K_V4.3 and K_V2.2 may be involved in this process.

Infantile hypertrophic pyloric stenosis: evaluation of three positional candidate genes, TRPC1, TRPC5 and TRPC6, by association analysis and re-sequencing

Infantile hypertrophic pyloric stenosis (IHPS) is the most common inherited form of gastrointestinal obstruction in infancy with a striking male preponderance. Infants present with vomiting due to gastric outlet obstruction caused by hypertrophy of the smooth muscle of the pylorus. Two loci specific to extended pedigrees displaying autosomal dominant inheritance have been identified. A genome scan identified loci on chromosomes 11q14-q22 and Xq23-q24 which are predicted to be responsible for a subset of smaller families with IHPS demonstrating non-Mendelian inheritance. The two linked chromosomal regions both harbour functional candidate genes which are members of the canonical transient receptor potential (TRPC) family of ion channels. Both TRPC5 (Xq23-q24) and TRPC6 (11q14-q22) have a potential role in smooth muscle control and hypertrophy. Here, we report suggestive evidence for a third locus on chromosome 3q12-q25 (Zmax = 2.7, p < 0.004), a region which harbours a third TRPC gene, TRPC1. Fine mapping of all three genes using a tagSNP approach and re-sequencing identified a SNP in the promoter region of TRPC6 and a missense variant in exon 4 of TRPC6 which may be putative causal variants.

Voltage-dependent Ca Current Identified in Freshly Isolated Interstitial Cells of Cajal (ICC) of Guinea-pig Stomach

The properties of voltage dependent Ca(2+) current (VDCC) were investigated in interstitial cells of Cajal (ICC) distributed in the myenteric layer (ICC-MY) of guinea-pig antrum. In tissue, ICC-MY showed c-Kit positive reactions and produced driving potentials with the amplitude and frequency of about 62 mV and 2 times min(-1), respectively, in the presence of 1 microM nifedipine. Single ICC-MY isolated by enzyme treatment also showed c-Kit immunohistochemical reactivity. These cells were also identified by generation of spontaneous inward current under K(+) -rich pipette solution. The voltage clamp experiments revealed the amplitude of - 329 pA inward current at irregular frequency. With Cs(+)-rich pipette solution at V(h)=-80 mV, ICC-MY produced voltage-dependent inward currents (VDIC), and nifedipine (1 microM) blocked VDIC. Therefore, we successfully isolated c-Kit positive single ICC from guinea-pig stomach, and found that ICC-MY potently produced dihydropiridine sensitive L-type voltage-dependent Ca(2+) currents (VDCC(L)).

Interstitial cells of Cajal in the normal gut and in intestinal motility disorders of childhood

Interstitial cells of Cajal (ICCs) are pacemaker cells which are densely distributed throughout the whole gastrointestinal tract. ICCs have important functions in neurotransmission, generation of slow waves and regulation of mechanical activities in the gastrointestinal tract, especially for the coordinated gastrointestinal peristalsis. Therefore, a loss of ICCs could result in gastrointestinal motor dysfunction. In recent years c-kit labeling has been widely used to study pathological changes of ICCs in gastrointestinal motility disorders. Paediatric gastrointestinal motility disorders such as hypertrophic pyloric stenosis, Hirschsprung's disease, total colonic aganglionosis, hypoganglionosis, intestinal neuronal dysplasia, internal anal sphincter achalasia, megacystis microcolon intestinal hypoperistalsis syndrome have been reported to be associated with loss or deficiency of ICCs networks. This review describes the distribution of ICCs in the normal gastrointestinal tract and its altered distribution in intestinal motility disorders of childhood.

Current management of hypertrophic pyloric stenosis

Hypertrophic pyloric stenosis (HPS) is a common condition affecting infants that presents with progressive projectile nonbilious vomiting. The pyloric portion of the stomach becomes abnormally thickened and manifests as gastric outlet obstruction. The cause is unknown. Pyloromyotomy remains the standard of treatment and outcome is excellent. This article reviews the diagnostic work up and imaging, preoperative resuscitation, the various surgical approaches used, and the effect of subspecialty training on outcomes after pyloromyotomy. Postoperative care and the variety of postoperative feeding regimens applied after pyloromyotomy are reviewed, as well as intra- and postoperative complications. Finally, medical management, in lieu of surgery, is discussed.

The Vomiting Neonate: A Review of the ACR Appropriateness Criteria and Ultrasound’s Role in the Workup of Such Patients

Ultrasound (US) plays a central role in the diagnostic imaging workup for infantile vomiting. This paper reviews the major causes of vomiting in the first months of life and the use of US and other modalities for their imaging assessment. The differential diagnostic possibilities are reviewed by examining 3 clinical scenarios of bilious vomiting during the first days of life, nonbilious vomiting since birth, and projectile vomiting first occurring after several weeks of life. These are the 3 scenarios that were used for the American College of Radiology (ACR) Appropriateness Criteria for Vomiting in Infants up to 3 Months of Age.

Single-nucleotide promoter polymorphism alters transcription of neuronal nitric oxide synthase exon 1c in infantile hypertrophic pyloric stenosis

Infantile hypertrophic pyloric stenosis (IHPS), characterized by enlarged pyloric musculature and gastric-outlet obstruction, is associated with altered expression of neuronal nitric oxide synthase (nNOS). Here we have studied molecular mechanisms by which nNOS gene expression is altered in pyloric tissues of 16 infants with IHPS and 9 controls. A significant decreased expression of total nNOS mRNA was found by quantitative RT-PCR in IHPS after normalization against GAPDH, which predominantly affected exon 1c with a reduction of 88% compared with controls (P < 0.001). After normalization against the neuronal-specific gene PGP9.5, expression of exon 1c was still decreased (P < 0.001), whereas expression of exon 1f was increased significantly (P = 0.001), indicating a compensatory up-regulation of this nNOS mRNA variant. DNA samples of 16 IHPS patients and 81 controls were analyzed for nNOS exon 1c promoter mutations and single-nucleotide polymorphism (SNP). Sequencing of the 5'-flanking region of exon 1c revealed mutations in 3 of 16 IHPS tissues, whereas 81 controls showed the wild-type sequence exclusively. Carriers of the A allele of a previously uncharacterized nNOS exon 1c promoter SNP (-84G --> A) had increased risk for development of IHPS (odds ratio, 8.0; 95% confidence interval, 2.5-25.6). Reporter gene assays revealed an unchanged promoter activity for mutations but a approximately 30% decrease for the -84A SNP (P < 0.001). In summary, our findings indicate that genetic alterations in the nNOS exon 1c regulatory region influence expression of the nNOS gene and may contribute to the pathogenesis of IHPS.

Distribution of heme oxygenase-2 in nerves and interstitial cells of Cajal in the normal pylorus and in infantile hypertrophic pyloric stenosis

CONTEXT

Interstitial cells of Cajal (ICCs) are pacemaker cells, which are of fundamental importance in regulating gastrointestinal motility. Recent evidence suggests that carbon monoxide is a neurotransmitter involved in neurotransmission between ICC and smooth muscle cells. Heme oxygenase-2 (HO-2) is the major physiological mechanism for the generation of carbon monoxide in the enteric nervous system.

OBJECTIVE

To investigate the immunocolocalization of HO-2 and ICCs in the normal pylorus and in infantile hypertrophic pyloric stenosis (IHPS).

DESIGN

Specimens from 18 infants with IHPS and 8 control specimens were examined using double-immunostaining with c-Kit and HO-2 antibodies. The immunolocalization was detected with the help of confocal laser scanning microscopy.

RESULTS

Abundant HO-2 immunoreactivity was found in ICCs in the smooth muscle layer of normal pylorus. There was a decrease in the number of ICCs and lack of HO-2 immunoreactivity in ICCs in IHPS.

CONCLUSIONS

The results of the present study provide the first evidence for the presence of HO-2 in ICCs in the normal human pylorus. The lack of ICCs and HO-2 in IHPS suggests impaired intracellular communication between ICCs and smooth muscle cells, contributing to motility dysfunction in IHPS.

Infantile hypertrophic pyloric stenosis

Infantile hypertrophic pyloric stenosis is a common condition affecting young infants; despite its frequency, it has been recognized only for a little over a century, and its etiology remains unknown. Nevertheless, understanding of the condition and of effective treatment have undergone a remarkable evolution in the 20th century, reducing the mortality rate from over 50% to nearly 0%. The lesion is characterized by gastric outlet obstruction and multiple anatomic abnormalities of the pyloric antrum. The antropyloric muscle is abnormally thickened and innervated, and the intervening lumen is obstructed by crowded and redundant mucosa. Recognition of the obstructive role of the mucosa led to discovery of effective surgical treatment. Accurate clinical diagnosis in patients in whom a thickened antropyloric muscle is not readily palpable can be difficult, resulting in delayed diagnosis and can lead to emaciation and electrolyte imbalance, making the patient a suboptimal surgical candidate. Current imaging techniques, particularly sonography, are noninvasive and accurate for identification of infantile hypertrophic pyloric stenosis. Successful imaging requires understanding of anatomic changes that occur in patients with this condition and plays an integral role in patient care. Accurate, rapid, noninvasive imaging techniques facilitate rapid referral of vomiting infants and prompt surgical treatment of more suitable surgical candidates.

The association of erythromycin and infantile hypertrophic pyloric stenosis: causal or coincidental?

The safety profile of erythromycin is notable for the frequent occurrence of intolerable gastrointestinal effects. One of the more serious of these is infantile hypertrophic pyloric stenosis (IHPS). A recent cluster of IHPS cases prompted an epidemiological investigation which identified oral erythromycin chemoprophylaxis of pertussis as the major risk factor. Evidence suggests an association between early postnatal erythromycin exposure and IHPS. There is no substantive evidence of a risk associated with prenatal exposure, with the single published case-control study to date producing negative findings. The epidemiological investigations of the association with early postnatal exposure have reported significantly elevated odds ratios but have a variety of methodological limitations that prevent definitive conclusions being made. Nevertheless, the concordance of findings across studies increases the strength of evidence favouring an association. The prominent gastrokinetic properties of erythromycin have been postulated as the mechanism behind this phenomenon. A comprehensive assessment of this potential adverse effect should consider its biological plausibility in light of known gastrointestinal physiology, its modulation by erythromycin, and the known pathophysiology of IHPS. Gastrointestinal motor activity in the fasted mammal consists of three phases, phase III being large amplitude contractions called migrating motor complexes (MMC) that can be initiated by motilin and erythromycin. The gastrokinetic effects of erythromycin are variable and complex and include effects on the timing, duration, amplitude and distribution of MMCs. It has been speculated that the motilinomimetic effects of erythromycin on antral smooth muscle function, such as the MMC, may mediate the effect via work hypertrophy. Although intuitively plausible and consistent with hypertrophic obstructive changes similar to IHPS observed in hyperplastic rat ileum after artificially induced mechanical obstruction, there is no direct evidence of this phenomenon. Further complicating the association is the limitations of our knowledge about the pathophysiology of IHPS, including numerous genetic abnormalities, increased parietal cell mass, and gastric hyperacidity. The implications of the reported findings with erythromycin on the benefit-risk profiles of newer macrolides and azalides must be considered. The available data on the comparative gastrokinetic properties of macrolides are significant for the potent gastrokinetic properties and its acid degradation products, the marked variation in gastrokinetic properties associated with macrolide ring size, and the requirement for specific glycosidic linkages at the C-3 and C-5 carbons of the macrolide ring. The variation in gastrokinetic properties associated with variations in molecular structure suggests that if the association between erythromycin and IHPS is causal it may not be a class effect.

A quantitative study of the neural changes underlying pyloric stenosis in dogs

This study aimed to quantify the neural changes in congenital pyloric stenosis in dogs and to study the comparative anatomy between this condition in dogs and that in infantile hypertrophic pyloric stenosis. Eight specimens from the pylorus of dogs with pyloric stenosis and six control specimens were examined using conventional histology and immunohistochemistry for a range of neural antigens. The changes in the proportion of nerves immunoreactive for each antigen were quantified and analysed statistically. The morphology of the nerves in the diseased dogs was similar to that in controls. Only vasoactive intestinal peptide was reduced in expression in dogs (median proportion in control dogs 0.57, in diseased dogs 0.17; P = 0.065). This study demonstrates both morphological similarities and significant differences between closely related conditions in dogs, humans and other species.

Loss of interstitial cells of Cajal and development of electrical dysfunction in murine small bowel obstruction

1. Partial obstruction of the murine ileum led to changes in the gross morphology and ultrastructure of the tunica muscularis. Populations of interstitial cells of Cajal (ICC) decreased oral, but not aboral, to the site of obstruction. Since ICC generate and propagate electrical slow waves in gastrointestinal muscles, we investigated whether the loss of ICC leads to loss of function in partial bowel obstruction. 2. Changes in ICC networks and electrical activity were monitored in the obstructed murine intestine using immunohistochemistry, electron microscopy and intracellular electrophysiological techniques. 3. Two weeks following the onset of a partial obstruction, the bowel increased in diameter and hypertrophy of the tunica muscularis was observed oral to the obstruction site. ICC networks were disrupted oral to the obstruction, and this disruption was accompanied by the loss of electrical slow waves and responses to enteric nerve stimulation. These defects were not observed aboral to the obstruction. 4. Ultrastructural analysis revealed no evidence of cell death in regions where the lesion in ICC networks was developing. Cells with a morphology intermediate between smooth muscle cells and fibroblasts were found in locations that are typically populated by ICC. These cells may have been the redifferentiated remnants of ICC networks. 5. Removal of the obstruction led to the redevelopment of ICC networks and recovery of slow wave activity within 30 days. Neural responses were partially restored in 30 days. 6. These data describe the plasticity of ICC networks in response to partial obstruction. After obstruction the ICC phenotype was lost, but these cells regenerated when the obstruction was removed. This model may be an important tool for evaluating the cellular/molecular factors responsible for the regulation and maintenance of the ICC phenotype.

Loss of interstitial cells of Cajal and development of electrical dysfunction in murine small bowel obstruction

1. Partial obstruction of the murine ileum led to changes in the gross morphology and ultrastructure of the tunica muscularis. Populations of interstitial cells of Cajal (ICC) decreased oral, but not aboral, to the site of obstruction. Since ICC generate and propagate electrical slow waves in gastrointestinal muscles, we investigated whether the loss of ICC leads to loss of function in partial bowel obstruction. 2. Changes in ICC networks and electrical activity were monitored in the obstructed murine intestine using immunohistochemistry, electron microscopy and intracellular electrophysiological techniques. 3. Two weeks following the onset of a partial obstruction, the bowel increased in diameter and hypertrophy of the tunica muscularis was observed oral to the obstruction site. ICC networks were disrupted oral to the obstruction, and this disruption was accompanied by the loss of electrical slow waves and responses to enteric nerve stimulation. These defects were not observed aboral to the obstruction. 4. Ultrastructural analysis revealed no evidence of cell death in regions where the lesion in ICC networks was developing. Cells with a morphology intermediate between smooth muscle cells and fibroblasts were found in locations that are typically populated by ICC. These cells may have been the redifferentiated remnants of ICC networks. 5. Removal of the obstruction led to the redevelopment of ICC networks and recovery of slow wave activity within 30 days. Neural responses were partially restored in 30 days. 6. These data describe the plasticity of ICC networks in response to partial obstruction. After obstruction the ICC phenotype was lost, but these cells regenerated when the obstruction was removed. This model may be an important tool for evaluating the cellular/molecular factors responsible for the regulation and maintenance of the ICC phenotype.

In vivo visualization of pyloric mucosal hypertrophy in infants with hypertrophic pyloric stenosis: is there an etiologic role?

OBJECTIVE

Infantile hypertrophic pyloric stenosis (IHPS) is a common condition which presents in infants at 2-12 weeks of postnatal life, and whose cause remains obscure. Multiple associated abnormalities have been recognized within the external hypertrophied pyloric muscle layer, but the internal component of the pyloric mucosa has received scant attention in the literature to date. Our purpose in this study was to show that pyloric mucosal redundancy is a constant finding in infants with IHPS, to discuss its possible cause, and to explore the hypothesis of a relationship between pyloric mucosal redundancy and the development of IHPS.

MATERIALS AND METHODS

We identified 102 consecutive infants with surgically confirmed IHPS and determined the thickness of the pyloric mucosa compared with the thickness of the surrounding hypertrophied muscle. Fifty-one infants who did not have pyloric stenosis served as controls.

RESULTS

Mean mucosal thickness in patients with IHPS approximated mean muscle thickness, with a ratio of 0.89. In infants with IHPS, the pyloric mucosa constitutes approximately one third of the cross-sectional diameter of the pyloric mass and fills and obstructs the pyloric canal.

CONCLUSION

Mucosal redundancy is a constant associated finding in IHPS. Although the origin of the redundancy and a cause-and-effect relationship are difficult to establish, our findings support the hypothesis that hypergastrinemia may be implicated in the pathogenesis of IHPS, and suggest that mucosal thickening could be implicated as one of the initiating factors in its development.

Selective neurotrophin deficiency in infantile hypertrophic pyloric stenosis

BACKGROUND/PURPOSE

Increasing evidence suggests that the enteric nervous system is under the control of neurotrophins. Nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4/5 (NT-4/5), promote differentiation, growth, and survival of various central and peripheral nervous system neurons. The biological effects of neurotrophins are mediated by the interactions with high-affinity tyrosine kinase receptors (TrkA, TrkB, TrkC). Recently, abnormalities of intramuscular innervation have been reported in infantile hypertrophic pyloric stenosis (IHPS). To further understand the reported abnormalities in pyloric innervation in IHPS, the authors analyzed the expression of Trk receptors and the neurotrophins content in IHPS.

METHODS

Full-thickness muscle biopsy specimens were obtained from 8 IHPS patients (age range, 23 to 41 days) at pyloromyotomy and from 8 age-matched controls without gastrointestinal disease at autopsy performed within 12 hours after death. Indirect immunohistochemistry was performed using ABC (Avidin Biotin peroxidase Complex) method with anti-Trk specific antibodies (A,B,C). Quantitative analysis was performed using sandwich-type ELISA for NGF, BDNF, NT-3, and NT-4/5.

RESULTS

The intensity of staining of the myenteric plexus for TrkA, TrkB, and TrkC was similar among IHPS and controls. There was a lack of TrkA-positive nerve fibers in IHPS compared with controls. The quantity of total NGF, NT-3, and BDNF in IHPS was significantly lower than in controls.

CONCLUSIONS

The reduced production of neurotrophins in IHPS may be responsible for the delay in the functional and structural maturation of pyloric innervation in IHPS. The lack of TrkA-positive nerve fibers in pyloric muscle may explain the abnormal intramuscular innervation in IHPS.

Absence of Epstein-Barr virus in smooth muscle cells of idiopathic hypertrophic pyloric stenosis

CONTEXT

The etiology of idiopathic hypertrophic pyloric stenosis (IHPS) is unknown. Epstein-Barr virus (EBV) infects smooth muscle cells and is associated with leiomyomas and leiomyosarcomas of immunocompromised persons, including persons with the acquired immunodeficiency syndrome.

OBJECTIVE

To determine whether EBV is causally associated with IHPS.

DESIGN

Biopsy samples of the pylorus were obtained from 10 infants with projectile vomiting and pyloric hypertrophy on ultrasound, with confirmation of hypertrophy at the time of pyloromyotomy. The presence of EBV infection was tested by in situ hybridization for EBV-encoded RNA 1 (EBER1) in smooth muscle cells of IHPS.

SETTING

Biopsy specimens were obtained from children treated for IHPS at a tertiary referral hospital and were tested in a clinical molecular diagnostics laboratory.

RESULTS

All of the 10 smooth muscle biopsies were negative for EBER1. Cellular U6 RNA was detected in all smooth muscle samples, confirming that the RNA in the specimens was intact and capable of detection by in situ hybridization.

CONCLUSIONS

The absence of EBER1 in 10 cases of clinically diagnosed and histopathologically confirmed cases of IHPS effectively excludes EBV infection of smooth muscle cells as a causal factor in the pathogenesis of IHPS.

Gastroduodenal disorders in children

Studies within the past year examining the mechanisms underlying infantile hypertrophic stenosis at the cellular and molecular level are reviewed. A number of new modalities, including electrogastrography, and the 13C octanoid acid breath test have been used in the study of normal and abnormal gastrointestinal motility, as well as for the characterization of patterns of development of gastric motility in early infancy. Several studies pertaining to the natural outcome, the mode of transmission, and the associated symptomatology of Helicobacter pylori were published, attesting that, despite the tremendous progress achieved in our understanding of H. pylori, important gaps remain in our knowledge of this microorganism. Newly described clinical presentations of eosinophilic gastroenteritis and food allergy will also be of interest to the reader.

Glial-derived growth factor signaling pathway in infantile hypertrophic pyloric stenosis

BACKGROUND/PURPOSE

Glial-derived growth factor (GDNF), which is the ligand of RET is reported to be essential for the development of enteric nervous system. A GDNF knockout mouse model has shown that the gastric region is a critical passing site between GDNF-RET-independent neuroblasts (colonizing the esophagus) and GDNF-RET-dependent neuroblasts (colonizing the small and large bowel). The earliest GDNF site of production is the mesenchyme and the outer smooth muscle cell (SMC) layer of the developing bowel. In the mature gastrointestinal tract the presence of GDNF is restricted to enteric glial cells. The aim of this study was to investigate the expression of GDNF and RET in infantile hypertrophic pyloric stenosis (IHPS).

METHODS

Full-thickness muscle biopsy specimens were obtained from 8 IHPS patients at pyloromyotomy and from 8 age-matched controls without gastrointestinal disease. Indirect immunohistochemistry was performed using avidin-biotin-peroxidase complex method with anti-GDNF and anti-RET antibodies. Quantitative analysis was performed using sandwich-type enzyme-linked immunosorbent assay (ELISA) for GDNF.

RESULTS

GDNF- and RET-positive nerve fibers were absent or markedly reduced in IHPS compared with controls. GDNF was expressed strongly by smooth muscle cells of both muscular layers in IHPS, whereas no GDNF expression was detected in pyloric muscle of controls. The quantity of total GDNF in IHPS was significantly higher than in controls (P < .01).

CONCLUSIONS

The lack or markedly decreased number of GDNF-positive nerve fibers in IHPS supports the hypothesis of a selective immaturity of the enteric glia in the muscular layers in IHPS. The strong expression of GDNF in smooth muscle cells in IHPS and the increased levels of GDNF in IHPS suggest a compensatory mechanism by which the smooth muscle cells continue to produce GDNF until maturation of the enteric glial cells occurs.

Increased local synthesis of epidermal growth factors in infantile hypertrophic pyloric stenosis

Infantile hypertrophic pyloric stenosis (IHPS) is characterized by hypertrophy of the pyloric muscle. The growth of smooth muscle cells is regulated by several growth factors. Epidermal growth factor (EGF) and heparin-binding EGF-like growth factor are potent mitogens for smooth muscle cells. In the present study, we investigated immunohistochemical localization of EGF and EGF-related peptides and EGF mRNA expression in pyloric smooth muscle cells to determine whether the EGF family is involved in the process of pyloric muscle hypertrophy in IHPS. Pyloric muscle biopsy specimens were obtained at the time of pyloromyotomy from 10 patients with IHPS. Control material included 10 pyloric muscle specimens taken at autopsy from age-matched cases without evidence of gastrointestinal disease. Indirect immunohistochemistry was performed using the avidin-biotin-peroxidase complex method with anti-EGF, anti-EGF receptor, and anti-heparin-binding EGF-like growth factor antibody. In situ hybridization was performed using digoxigenin-labeled EGF-specific oligonucleotide probe. The pattern of immunoreactivity in pyloric muscle with EGF, EGF receptor, and heparin-binding EGF-like growth factor was similar in all specimens. There was a marked increase in EGF, EGF receptor, and heparin-binding EGF-like growth factor immunoreactivity and EGF mRNA expression in smooth muscle cells in pyloric circular and longitudinal muscle from patients with IHPS compared with control specimens. These data suggest that the upregulated local synthesis of EGF and EGF-related peptides in pyloric muscle may play a critical role in the development of pyloric muscle hypertrophy in IHPS.