Embryogenesis of tracheo esophageal anomalies: a review

Laryngotracheoesophageal Cleft Type IV in a Preterm Neonate. A Case Report and Literature Review

We present a case of a preterm neonate with a type IV laryngo-tracheo-oesophageal cleft, an uncommon congenital malformation, resulting from the failure of separation of the trachea and the oesophagus during fetal development, often associated with other deformities as well. Data in the literature shows that the long-term morbidity from the entity has declined over the last decades, even though prognosis remains unfavourable for types III and IV. This report emphasizes the complex issues neonatologists are faced with, when treating neonates with this rare disorder in the first days of life, what will raise suspicion of this rare medical entity, and that direct laryngoscopy/bronchoscopy finally depicts the exact extension of the medical condition. At the same time extensive evaluation for coexisting congenital anomalies should be performed. For all the above reasons, these neonates should be treated in specialized tertiary pediatric centers for multidisciplinary prompt management, which may improve, the outcome.

Disruption of BMP4 signaling is associated with laryngeal birth defects in a mouse model

Laryngeal birth defects are considered rare, but they can be life-threatening conditions. The BMP4 gene plays an important role in organ development and tissue remodeling throughout life. Here we examined its role in laryngeal development complementing similar efforts for the lung, pharynx, and cranial base. Our goal was to determine how different imaging techniques contribute to a better understanding of the embryonic anatomy of the normal and diseased larynx in small specimens. Contrast-enhanced micro CT images of embryonic larynx tissue from a mouse model with Bmp4 deletion informed by histology and whole-mount immunofluorescence were used to reconstruct the laryngeal cartilaginous framework in three dimensions. Laryngeal defects included laryngeal cleft, laryngeal asymmetry, ankylosis and atresia. Results implicate BMP4 in laryngeal development and show that the 3D reconstruction of laryngeal elements provides a powerful approach to visualize laryngeal defects and thereby overcoming shortcomings of 2D histological sectioning and whole mount immunofluorescence.

Development of the foregut and the formation of the trachea and esophagus in rat embryos. A symphony of confusion

Introduction: During embryonic development, the trachea emerges from an area of the foregut, which is often referred to as "anterior" or "common" foregut tube or simply foregut. To explain this process of differentiation, four competing models exist to date. The outgrowth and watershed models propose a foregut that remains constant in length. In the outgrowth model, the trachea buds off and elongates from the foregut, while in the watershed model, a mesenchymal wedge splits the growing foregut into the trachea and esophagus. In contrast, the septation model proposes a cranial splitting and thus a shortening of the "common" foregut tube into the trachea and esophagus by an emerging septum. Finally, the splitting and extension model describes an interaction of cranial splitting of the foregut and simultaneous caudal tracheal and esophageal growth. Methods: Here we examine the development of the undifferentiated foregut by micro computed tomography, which allows precise measurements. Results: Our results show that this area of the foregut transforms into the larynx, a process, which is independent from tracheal and esophageal development. Discussion: These observations are only consistent with the outgrowth model.

Management of Symptomatic Grade I and II Laryngeal Cleft: Experience of a Tertiary Care Center and Review of Literature

Laryngeal cleft is a rare pathology and needs a high index of suspicion for diagnosis. Various classifications are used but the Inglis classification which describes 4 grades of cleft is most widely accepted. Grade 3 and 4 clefts are very rare and are usually associated with other congenital abnormalities. Grade 1 and 2 clefts are more common and can be easily corrected with good outcomes. We are presenting our experience with 9 cases of low grade (Grade 1 and 2) laryngeal cleft which were managed successfully in our department. Out of the 9 cases 4 failed conservative management and required a trans-oral repair. All patients improved with management, except one who intermittently developed another episode of pneumonia 2 months' post-surgery. However satisfactory cleft obliteration was confirmed on endoscopy and the patient has been under close follow up ever since. Majority of low grade laryngeal clefts can be managed with dietary modifications and feeding rehabilitation. Those who do not respond usually require surgical repair with near complete resolution of symptoms.

Congenital tracheal defects: embryonic development and animal models

Tracheal anomalies are potentially catastrophic congenital defects. As a newborn begins to breathe, the trachea needs to maintain an appropriate balance of elasticity and rigidity. If the tracheal cartilages are disorganized or structurally weak, the airways can collapse, obstructing breathing. Cartilage rings that are too small or too rigid can also obstruct breathing. These anomalies are frequently associated with craniofacial syndromes, and, despite the importance, are poorly understood. In this review, we summarize the spectrum of pathological phenotypes of the trachea and correlate them with the molecular events uncovered in mouse models.

Asymptomatic severe laryngotracheoesophageal cleft (LTEC) in a preterm newborn

Objectives

We are presenting a unique case of severe laryngo-tracheo-esophageal cleft in a preterm infant who remained asymptomatic for several days after birth. Laryngo-tracheo-esophageal cleft (LTEC) is a rare congenital anomaly, representing approximately 0.2–1.5% of congenital laryngeal malformations [Merei JM, Hutson JM. Embryogenesis of tracheo esophageal anomalies: a review. Pediatr Surg Int 2002;18:319–26]. There is an abnormal, posterior, sagittal communication between the larynx and the pharynx, which may extend downward between the trachea and the esophagus.

Case presentation

We report a case of LTEC in a preterm newborn whose mother had severe polyhydramnios. A preterm 34-week gestation female newborn was born in our institution whose mother had severe polyhydramnios during third trimester. She was postnatally diagnosed to have type 3 LTEC by the 19th day after birth. In the presence of a large common tracheo-esophageal cavity, the baby did not develop aspiration or respiratory distress despite feeding from birth.

Conclusions

This case report illustrates the many factors and the probable mechanisms involved in preventing aspiration.

Histological, immunohistochemical and transcriptomic characterization of human tracheoesophageal fistulas

Esophageal atresia (EA) and tracheoesophageal fistula (TEF) are relatively frequently occurring foregut malformations. EA/TEF is thought to have a strong genetic component. Not much is known regarding the biological processes disturbed or which cell type is affected in patients. This hampers the detection of the responsible culprits (genetic or environmental) for the origin of these congenital anatomical malformations. Therefore, we examined gene expression patterns in the TEF and compared them to the patterns in esophageal, tracheal and lung control samples. We studied tissue organization and key proteins using immunohistochemistry. There were clear differences between TEF and control samples. Based on the number of differentially expressed genes as well as histological characteristics, TEFs were most similar to normal esophagus. The BMP-signaling pathway, actin cytoskeleton and extracellular matrix pathways are downregulated in TEF. Genes involved in smooth muscle contraction are overexpressed in TEF compared to esophagus as well as trachea. These enriched pathways indicate myofibroblast activated fibrosis. TEF represents a specific tissue type with large contributions of intestinal smooth muscle cells and neurons. All major cell types present in esophagus are present-albeit often structurally disorganized-in TEF, indicating that its etiology should not be sought in cell fate specification.

Diagnosis and management of complete tracheal rings with concurrent tracheoesophageal fistula

OBJECTIVE

Characterize patients with complete tracheal rings and tracheoesophageal fistula (TEF) and summarize management options.

METHODS

A systematic review of patients under 18 years of age with complete tracheal rings and TEF was conducted. Authors were contacted for additional patient information and new cases were added. Patients with iatrogenic TEF and tracheal stenosis due to other causes were excluded.

RESULTS

Sixteen patients with a median (IQR) follow-up of 10 months (3-12 months) were identified. All had a distal TEF with complete tracheal rings distal to the TEF. There were 10 (63%) type C esophageal atresia + TEF (EA/TEF), and 1 (6%) type D (5 missing data). Median (IQR) airway diameter was 2 mm (1.5-2.2 mm). Complete tracheal rings were diagnosed prior to TEF repair in 5 (31.3%) patients, after ≥1 failed extubation in 3 (12.5%) patients, and intra-operatively during respiratory distress in 1 patient. Ten patients (62.5%) were intubated with an endotracheal tube and one with a 6 Fr flexible aortic canula (5 missing data). Four patients with an endotracheal tube for TEF repair developed ventilatory problems. Complete tracheal rings were repaired in 9 (56%) patients (8 slide tracheoplasty, 1 pericardial patch) and followed conservatively in 3 (19%). One patient required tracheotomy. Four patients died.

CONCLUSIONS

Complete tracheal rings with concurrent TEF is a rare entity that pose challenges for ventilatory management during operative repair. Bronchoscopy prior to TEF repair is critical to allow for proper preoperative planning.

Type IV Laryngotracheoesophageal Cleft Associated with Type III Esophageal Atresia in 1p36 Deletions Containing the RERE Gene: Is There a Causal Role for the Genetic Alteration?

The causes of embryological developmental anomalies leading to laryngotracheoesophageal clefts (LTECs) are not known, but are proposed to be multifactorial, including genetic and environmental factors. Haploinsufficiency of the RERE gene might contribute to different phenotypes seen in individuals with 1p36 deletions. We describe a neonate of an obese mother, diagnosed with type IV LTEC and type III esophageal atresia (EA), in which a 1p36 deletion including the RERE gene was detected. On the second day of life, a right thoracotomy and extrapleural esophagus atresia repair were attempted. One week later, a right cervical approach was performed to separate the cervical esophagus from the trachea. Three months later, a thoracic termino-terminal anastomosis of the esophagus was performed. An anterior fundoplication was required at 8 months of age due to severe gastroesophageal reflux and failure to thrive. A causal role of 1p36 deletions including the RERE gene in the malformation is proposed. Moreover, additional parental factors must be considered. Future studies are mandatory to elucidate genomic and epigenomic susceptibility factors that underlie these congenital malformations. A multiteam approach is a crucial factor in the successful management of affected patients.

Tracheal agenesis in a new born: lessons learnt

Tracheal agenesis is a rare but fatal congenital tracheal malformation. Lack of prenatal symptom and a typical clinical presentation lead to failure to arrive at a correct diagnosis and confusion during resuscitation. We report a case of a newborn male child with type 2 tracheal agenesis. Despite a typical presentation, diagnosis was delayed after unsuccessful intubation, examination under anaesthesia and emergency tracheostomy. The embryology, diagnostic criteria and potential treatment options are discussed. This case report is valuable in increasing awareness of this rare condition and will help us in being better prepared in managing these children. Future studies should aim to find the optimal replacement for the tracheal.

Tracheal agenesis in a new born: lessons learnt

Tracheal agenesis is a rare but fatal congenital tracheal malformation. Lack of prenatal symptom and a typical clinical presentation lead to failure to arrive at a correct diagnosis and confusion during resuscitation. We report a case of a newborn male child with type 2 tracheal agenesis. Despite a typical presentation, diagnosis was delayed after unsuccessful intubation, examination under anaesthesia and emergency tracheostomy. The embryology, diagnostic criteria and potential treatment options are discussed. This case report is valuable in increasing awareness of this rare condition and will help us in being better prepared in managing these children. Future studies should aim to find the optimal replacement for the tracheal.

Laryngeal cleft type IV: One pathology, two different presentations

Laryngotracheoesophageal cleft is a rare congenital malformation where a communication exists between the aero-digestive tracts that is associated with high morbidity and mortality. In this case series, we describe our experience with two neonates evaluated in our institution with two diverse initial presentations and symptomatology of type IV laryngotracheoesophageal clefts. One patient presented with acute distress and respiratory failure due to bowel contents obstructing the trachea and the other presented with mild subcostal retractions and inspiratory stridor without overt respiratory failure. Most importantly, not every patient with type IV laryngotracheoesophageal clefts will present with fulminant respiratory difficulty. This prompted a literature review.

Low inter-arytenoid height: a subclassification of type 1 laryngeal cleft diagnosis and management

OBJECTIVE

To report our experience of patients with type 1 laryngeal cleft, (including low inter-arytenoid height) who failed conservative management over a five year period. We describe the diagnostic elements of the history, examination at laryngobronchoscopy and provide a management algorithm including the use of inter-arytenoid submucosal injection of gelfoam as a temporary therapeutic as well as diagnostic tool.

METHODS

A retrospective case note review over a five year period was undertaken to review all cases of type 1 laryngeal cleft who failed conservative management. Presenting symptoms, diagnostic procedures, surgical interventions and clinical outcomes were reviewed.

RESULTS

Seventeen patients were identified. Chronic cough was the most consistent feature in the history (100%). All patients underwent a microlaryngoscopy with binocular microlaryngeal assessment. Six patients (35%) underwent gelfoam injection; four of these went on to a formal repair. The remaining 11 all had a repair performed without injection. The success of surgical repair was 80% (12/15) however in the other three, all had improvement in symptoms.

CONCLUSIONS

Type 1 laryngeal cleft anomalies may extend beyond that described by Benjamin and Inglis. An appropriate history as well as binocular inspection at the time of laryngoscopy is essential. Injection augmentation offers a safe tool in the assessment and management, and endoscopic surgical repair remains the standard for definitive therapy in those that fail conservative management.

TACRD and VACTERL associations in a fetus: case report and review of the literature

Tracheal agenesis is a rare and potentially lethal congenital anomaly. The incidence is less than 1/50,000, with a male:female ratio of 2:1. We report the case of a male fetus with complete agenesis of the trachea and a tracheoesophageal fistula arising from the esophagus that connected through the carina, as well as several abnormalities (congenital cardiac abnormalities, duodenal atresia, vertebral defects, anal atresia, renal defects, limb defects, and diaphragmatic hernia). To our knowledge, few cases of infants with VACTERL or TACRD association have been reported to date. Here, we report a new case of a fetus that showed the full range of VACTERL and TACRD associations.

Adriamycin-Induced Models of VACTERL Association

Animal models are of great importance for medical research. They have enabled analysis of the aetiology and pathogenesis of complex congenital malformations and have also led to major advances in the surgical and therapeutic management of these conditions. Animal models allow us to comprehend the morphological and molecular basis of disease and consequently to discover novel approaches for both surgical and medical therapy. The anthracycline antibiotic adriamycin was incidentally found to have teratogenic effects on rats, producing a range of defects remarkably similar to the VACTERL association of congenital anomalies in humans, providing a reproducible animal model of this condition. VACTERL association is a spectrum of birth defects which includes vertebral, anal, cardiovascular, tracheo-oesophageal, renal and limb anomalies. In recent years, adriamycin rodent models of VACTERL have provided valuable insights into the pathogenesis of this complex association, particularly in relation to tracheo-oesophageal malformations. The adriamycin rat model and adriamycin mouse model are now well established in the investigation of the morphology of faulty organogenesis and the regulation of gene expression in tracheo-oesophageal anomalies.

Tracheal agenesis: approach towards this severe diagnosis. Case report and review of the literature

Tracheal agenesis (TA) is a severe congenital disorder with often an unexpected emergency presentation. There is complete or partial absence of the trachea below the larynx, with presence or absence of a tracheoesophageal fistula (TOF). A neonate with TA is described, and another 48 cases found in literature are reviewed. Due to absence of a TOF, five cases were diagnosed prenatally because of congenital high airway obstruction syndrome (CHAOS). When a TOF is present, polyhydramnion and several other congenital malformations seen on the ultrasound examination should alert clinicians of potential tracheal problems. Prenatal magnetic resonance imaging (MRI) may provide a definitive diagnosis. Postnatal diagnosis is based on recognition of specific clinical signs in the newborn with TA: respiratory distress with breathing movement without appropriate air entry, no audible cry, and failed endotracheal intubation. Despite progress in surgical interventions, mortality remains high. Prenatal diagnosis of TA is possible, but only if a TOF is absent resulting in CHAOS. Prenatal diagnosis of polyhydramnion and other congenital malformation should alert clinicians of potential tracheal problems. Prenatal MRI may provide a definitive diagnosis.

Laryngo-tracheo-oesophageal clefts

A laryngo-tracheo-esophageal cleft (LC) is a congenital malformation characterized by an abnormal, posterior, sagittal communication between the larynx and the pharynx, possibly extending downward between the trachea and the esophagus. The estimated annual incidence of LC is 1/10,000 to 1/20,000 live births, accounting for 0.2% to 1.5% of congenital malformations of the larynx. These incidence rates may however be underestimated due to difficulty in diagnosing minor forms and a high mortality rate in severe forms. A slightly higher incidence has been reported in boys than in girls. No specific geographic distribution has been found. Depending on the severity of the malformation, patients may present with stridor, hoarse cry, swallowing difficulties, aspirations, cough, dyspnea and cyanosis through to early respiratory distress. Five types of laryngo-tracheo-esophageal cleft have been described based on the downward extension of the cleft, which typically correlates with the severity of symptoms: Type 0 laryngo-tracheo-esophageal cleft to Type 4 laryngo-tracheo-esophageal cleft. LC is often associated with other congenital abnormalities/anomalies (16% to 68%), mainly involving the gastro-intestinal tract, which include laryngomalacia, tracheo-bronchial dyskinesia, tracheo-bronchomalacia (mostly in types 3 and 4), and gastro-esophageal reflux disease (GERD). The syndromes most frequently associated with an LC are Opitz/BBB syndrome, Pallister Hall syndrome, VACTERL/VATER association, and CHARGE syndrome. Laryngeal clefts result from failure of fusion of the posterior cricoid lamina and abnormal development of the tracheo-esophageal septum. The causes of the embryological developmental anomalies leading to LC are not known but are thought to be multifactorial. LC appears to be mostly sporadic although some familial cases with suspected autosomal dominant transmission have been reported. The age of diagnosis depends mainly on the severity of the clinical symptoms and therefore on the extent of the LC. Diagnosis is made either based on clinical manifestations or on investigations, such as endoscopy, X-ray, CT scan, performed for other conditions. Differential diagnoses include tracheo-bronchial fistula, gastro-esophageal reflux disease and neurological swallowing disorders, as well as laryngomalacia and laryngeal palsy. Prenatal diagnosis of LC has never been reported, although associated anomalies may be detected on fetal ultrasonography. Once the cleft is diagnosed, it is essential to determine its length to orient the management and treatment approach. Management involves maintenance of satisfactory ventilation, prevention of secondary pulmonary complications as a result of repeated aspirations, and adequate feeding. Endotracheal intubation may be required for respiratory distress in severe cases. Treatment requires endoscopic or external surgery to close the cleft. Surgery should be performed as early as possible to avoid complications related to aspiration and gastric reflux, except in type 0 and type 1 cases in which conservative measures must first be attempted. The prognosis is variable depending on the severity of the LC and associated malformations. Early diagnosis and appropriate treatment and management help to reduce mortality and morbidity.

Abnormal notochord branching is associated with foregut malformations in the adriamycin treated mouse model

Oesophageal atresia (OA) and tracheooesophageal fistula (TOF) are relatively common human congenital malformations of the foregut where the oesophagus does not connect with the stomach and there is an abnormal connection between the stomach and the respiratory tract. They require immediate corrective surgery and have an impact on the future health of the individual. These abnormalities are mimicked by exposure of rat and mouse embryos in utero to the drug adriamycin. The causes of OA/TOF during human development are not known, however a number of mouse mutants where different signalling pathways are directly affected, show similar abnormalities, implicating multiple and complex signalling mechanisms. The similarities in developmental outcome seen in human infants and in the adriamycin treated mouse model underline the potential of this model to unravel the early embryological events and further our understanding of the processes disturbed, leading to such abnormalities. Here we report a systematic study of the foregut and adjacent tissues in embryos treated with adriamycin at E7 and E8 and analysed between E9 and E12, comparing morphology in 3D in 149 specimens. We describe a spectrum of 8 defects, the most common of which is ventral displacement and branching of the notochord (in 94% of embryos at E10) and a close spatial correspondence between the site of notochord branching and defects of the foregut. In addition gene expression analysis shows altered dorso-ventral foregut patterning in the vicinity of notochord branches. This study shows a number of features of the adriamycin mouse model not previously reported, implicates the notochord as a primary site of disturbance in such abnormalities and underlines the importance of the model to further address the mechanistic basis of foregut congenital abnormalities.

Embryology of anorectal malformations

Today, the normal and abnormal development of the hindgut is still a matter of speculation. However, as the result of recent studies in appropriate animal models, most embryologic events that finally lead to abnormal hindgut development are better known than in the past: (1) the process of maldevelopment starts in early embryonic stages; (2) the cloacal membrane is always too short in its dorsal part, thus, the dorsal cloaca is missing; and (3) as a result, the hindgut remains attached to the sinus urogenitalis, forming the recto-urethral fistula. In the past, an impaired process of septation was believed to be the main cause of abnormal hindgut development. In contrast to this, our results indicate that the development of the septum is more passive than active. Furthermore, the results of our studies in normal and abnormal development indicate that (1) the embryonic cloaca never passes through a stage that is similar to any form of anorectal malformation in neonates, including the so-called "cloacas" in female embryos, and (2) to explain abnormal development, studies in abnormal embryos are mandatory.

Mesenchymal expression of Tbx4 gene is not altered in Adriamycin mouse model

PURPOSE

The Adriamycin mouse model (AMM) is a reproducible teratogenic model of esophageal atresia/tracheo-esophageal fistula (EA/TEF). Tbx4 is a member of the T-box family of transcription factor genes, which is reported to play a key role in separation of the respiratory tract and the esophagus. Up-regulation of Tbx4 is reported to cause TEF in the chick. Optical projection tomography (OPT) is a technique that allows three-dimensional (3D) imaging of gene expression in small tissue specimens in an anatomical context. The aim of this study was to investigate the temporo-spatial expression of Tbx4 during the critical period of separation of the trachea and esophagus in normal and Adriamycin treated embryos using OPT.

MATERIALS AND METHODS

Time-mated CBA/Ca mice received intraperitoneal injections of Adriamycin (6 mg/kg) or saline on days 7 and 8 of gestation. Embryos were harvested on days 9-12, stained following whole mount in situ hybridization with labeled RNA probes to detect Tbx4 transcripts (n = 5 for each treatment/day of gestation). Immunolocalization with the endoderm marker Hnf3beta was used to visualize morphology. Embryos were scanned by OPT to obtain 3D representations of gene expression domains. Animal licence no. B100/4106.

RESULTS

OPT elegantly revealed Tbx4 gene expression in both controls and in the disorganized pulmonary mesenchyme in the treated embryos. Although characteristic morphological abnormalities were observed in Adriamycin treated embryos, there was no significant difference in Tbx4 transcript distribution around lung primordia in comparison with control embryos.

CONCLUSION

Although previously reported morphological abnormalities of notochord and esophagus were observed in AMM, Tbx4 gene expression was unaltered, suggesting that esophageal anomalies can occur in the presence of normal Tbx4 gene expression in this model.

Tracheal agenesis as a rare cause of difficult intubation in a newborn with respiratory distress: a case report

Introduction

Tracheal agenesis is a very rare congenital airway anomaly. It may pose a great challenge to the first attending physician both in diagnosis and in establishing the airway during the first day of life.

Case presentation

We report a newborn Malay baby boy with trachea agenesis (type III by Floyd's classification) who presented with severe respiratory distress immediately after birth. Clinical diagnosis in this case was not straightforward, as it started with difficulty in intubation followed by an unsuccessful emergency tracheostomy in the neonatal intensive care unit. Urgent surgical neck exploration with endoscopic examination in the general operating theatre revealed the final diagnosis. The authors present a short description of the embryopathology and diagnostic criteria of the abnormality.

Conclusion

We hope this case presentation will be valuable in increasing the awareness of physicians about this rare cause of tracheal obstruction or difficult intubation.

Tracheal agenesis as a rare cause of difficult intubation in a newborn with respiratory distress: a case report

INTRODUCTION

Tracheal agenesis is a very rare congenital airway anomaly. It may pose a great challenge to the first attending physician both in diagnosis and in establishing the airway during the first day of life.

CASE PRESENTATION

We report a newborn Malay baby boy with trachea agenesis (type III by Floyd's classification) who presented with severe respiratory distress immediately after birth. Clinical diagnosis in this case was not straightforward, as it started with difficulty in intubation followed by an unsuccessful emergency tracheostomy in the neonatal intensive care unit. Urgent surgical neck exploration with endoscopic examination in the general operating theatre revealed the final diagnosis. The authors present a short description of the embryopathology and diagnostic criteria of the abnormality.

CONCLUSION

We hope this case presentation will be valuable in increasing the awareness of physicians about this rare cause of tracheal obstruction or difficult intubation.

Sonic hedgehog gene expression in nitrofen induced hypoplastic lungs in mice

BACKGROUND

The pathogenesis of congenital diaphragmatic hernia (CDH) is unknown. The sonic hedgehog (Shh) cascade is crucial for the patterning of the early respiratory system in mice. Optical Projection Tomography (OPT) is a new tool for 3D imaging small biological specimens that enables us to visualise both the anatomy of developing organs and gene expression localised in the context of normal or abnormal anatomy. We visualised Shh gene expression patterns in the nitrofen treated and control mouse lung buds at early stages of lung development.

MATERIALS AND METHODS

Time-mated CD1 female mice (n = 5) received oral administration of 100 mg of the herbicide 2,4-dichlorophenyl-p-nitrophenylether (nitrofen) (WAKO Chemical, Osaka, Japan) in 1 ml of olive oil or olive oil alone at 7 days of gestation. Embryos were harvested on gestation days 9-12, and stained following whole mount in situ hybridisation with labelled RNA probes to detect Shh transcripts at each stage. Embryos were scanned by OPT to obtain 3D representations of gene expression domains in the context of the changing morphology of the embryo.

RESULTS

OPT analysis of Shh transcript distribution clearly revealed gene expression in both groups. In treated embryos, there were no significant changes in Shh transcript distribution in lung buds in comparison with control embryos.

CONCLUSION

Although altered Shh expression in the hypoplastic lung has been reported in late gestation, the present study did not reveal any significant alterations in pulmonary Shh spatial transcript distribution or gene expression level during the early gestation in nitrofen CDH model. It would be of great interest in future studies to use OPT approach to investigate pulmonary expression of Shh and other regulatory genes both during early and late stages of lung development in order to provide new insights into the pathogenesis of pulmonary hypoplasia.

Noncommunicating tubular duplication of the upper pouch in esophageal atresia without fistula

We report a unique combination of an esophageal atresia without fistula associated with a tubular noncommunicating esophageal duplication. The diagnosis was made at delayed repair and led to a successful outcome.

Congenital abnormalities of intrathoracic airways

Multidetector CT has broadened the potential of imaging to demonstrate anomalies of the lung and the tracheobronchial tree with increasing frequency. Two-and three-dimensional reformatting improve the understanding of complex tracheobronchial anomalies. Most congenital tracheobronchial anomalies are rare and almost always nonsymptomatic; however, some may be confused with or even responsible for respiratory disease. Tracheal and accessory cardiac bronchi are among the most frequent anomalies, but other ectopic or supernumerary lung buds, developmental tracheobronchial interruption, obstruction, or compression, communicating bronchopulmonary foregut malformations, and bronchial malformations associated with anomalies of situs can be detected, even late after birth.

Successful reconstruction of communicating bronchopulmonary foregut malformation associated with laryngotracheoesophageal cleft

A full-term newborn male infant presented with dyspnea and cleft lip and palate. He was thought to have esophageal atresia with tracheoesophageal fistula. He underwent bronchoscopy before operation that showed a laryngotracheoesophageal cleft (LTEC) type III. The left main bronchus originated from the lower esophagus. His diagnosis was communicating bronchopulmonary foregut malformation (CBPFM) type IA associated with LTEC type III. Enhanced chest computed tomographic scan showed the left pulmonary artery originated from the descending aorta. Staged operations were indicated. At first, reconstruction of the left pulmonary artery was done at 3 months of age. Then at 6 months of age, operations for LTEC (tracheoplasty and esophagostomy) and CBPFM left bronchoplasty were performed. Reconstruction of esophagus was performed at age of 1 year. He is now 3 years old and doing well with a mild degree of bronchomalacia. This is the first report of total reconstruction of CBPFM type IA associated with LTEC.

The lung primordium an outpouching from the foregut! Evidence-based dogma or myth?

BACKGROUND/PURPOSE

This study examines and challenges the "evidence-based legitimacy" of the theory, "the lung primordium is an outpouching from the foregut."

METHOD

A literature review was undertaken using computer database, journals, and relevant anatomical and embryological texts.

RESULTS

The independent path of development taken by the tracheobronchial system and the oesophagus once identified as separate entities; the lack of morphologic, molecular, biological, and genetic supportive evidence for the "common-origin" theory; the distinct longitudinal line of demarcation between the nonsegmented muscles of the esophagus and the highly segmented cartilaginous structure of the tracheobronchial tree; the absence of a tracheoesophageal septum in the process of separation; the differences in epithelial lining; and the diametrically opposed mucociliary cascade of the upper airway vs the mucociliary escalator of the tracheobronchial tree all seriously challenge the authenticity of a common origin to these 2 entities.

CONCLUSION

To the extent that the foregut is seen as consisting of 2 separate semitubular splanchnopleuric entities ventrodorsally juxtaposed, it is true that the lung primordium as an outpouching of, and not from, the foregut. This must never be confused with the notion that the esophagus and tracheobronchial tree have a common origin. In fact, they develop from 2 completely separate segments of the trilaminar germ disk, but because of head fold development are brought together to create a common tracheoesophageal chamber that is later separated, facilitated by the prochordal membrane diverticulum.

Intrinsic esophageal innervation in esophageal atresia without fistula

Esophageal atresia and tracheo-esophageal fistula (EA + TEF) are often associated with malformations of neural crest origin. Esophageal innervation is also derived from the neural crest and it is abnormal in EA + TEF in which there is motor dysfunction. Our aim was to examine the intrinsic esophageal innervation in children with isolated EA in which different embryogenic mechanisms might be involved. Specimens from the proximal and distal esophageal segments of 6/35 patients who had esophageal replacement for isolated EA between 1965 and 2006 were suitable for the study. They were sectioned and immunostained with anti-neurofilament (NF) and anti-S-100 antibodies. The muscle and neural surfaces on each section were measured with the assistance of image processing software. The surface of the ganglia and the number of neurons per ganglion were determined at high power microscopy. The findings were compared with those of six autopsy specimens from newborns dead of other diseases by means of standard statistical tests and a significance threshold of P < 0.05. Unmatched age/size of babies in isolated EA and control groups precluded comparison of the relative surfaces occupied by neural elements. Patients with pure EA had denser fibrilar network and larger ganglia than controls. The number of neurons/ganglion were similar in both groups although the cells from EA patients were larger. The findings were similar at both esophageal levels studied. In spite of methodologic biases, it seems that intrinsic esophageal fibrilar network is denser and the intramural ganglia larger with larger cells in patients with pure EA than in controls on both esophageal ends of the organ. These neural anomalies are only in part reminiscent of those described in regular EA/TEF but may as well explain esophageal dysfunction in patients with repaired isolated EA.

Visualizing expression patterns of Shh and Foxf1 genes in the foregut and lung buds by optical projection tomography

Congenital malformations of the foregut are common in humans. The respiratory and digestive tubes are both derived by division of the foregut primordium. Sonic hedgehog (Shh) and Fork head box F1 (Foxf1) genes encode regulatory molecules that play a pivotal role in gut and lung morphogenesis and are therefore important candidate genes to be examined in models of foregut developmental disruption. Optical projection tomography (OPT) is a new, rapid and non-invasive technique for three-dimensional (3D) imaging of small biological tissue specimens that allows visualization of the tissue distribution of RNA in developing organs while also recording morphology. To explore the application of OPT in this context, we visualized Shh and Foxf1 gene expression patterns in the mouse foregut and lung buds at several stages of development. Time-mated CBA/Ca mice were harvested on embryonic days 9-12. The embryos were stained following whole mount in situ hybridization with labelled RNA probes to detect Shh and Foxf1 transcripts at each stage. The embryos were scanned by OPT to obtain 3D representations of gene expression domains in the context of the changing morphology of the embryo. OPT analysis of Shh and Foxf1 expression in the foregut and lung buds revealed extra details of the patterns not previously reported, particularly in the case of Foxf1 where gene expression was revealed in a changing pattern in the mesenchyme around the developing lung. Shh expression was also revealed in the epithelium of the lung bud itself. Both genes were detected in complementary patterns in the developing bronchi as late as E12, showing successful penetration of molecular probes and imaging at later stages. OPT is a valuable tool for revealing gene expression in an anatomical context even in internal tissues like the foregut and lung buds across stages of development, at least until E12. This provides the possibility of visualizing altered gene expression in an in vivo context in genetic or teratogenic models of congenital malformations.

Adriamycin produces a reproducible teratogenic model of vertebral, anal, cardiovascular, tracheal, esophageal, renal, and limb anomalies in the mouse

BACKGROUND/PURPOSE

The Adriamycin rat model is an established model for vertebral, anal, cardiac, tracheal, esophageal, renal, and limb (VACTERL) anomalies and gastrointestinal atresias. Mice are the foremost mammal studied by developmental biologists, providing greater availability of molecular probes, antibodies, and transferable knowledge with transgenic studies. Only tracheoesophageal malformations have been previously described in the Adriamycin mouse model. The aim of this study was to carry out a dose-response analysis of the teratogenicity of Adriamycin in the mouse to determine the effect of the dose and timing of exposure in producing tracheoesophageal malformations and show if it causes other VACTERL anomalies.

METHODS

CBA/Ca mice were accurately time mated (n = 30). Four different doses (0 [saline], 4, 5, and 6 mg/kg) of Adriamycin (EBEWE Pharma Ges.m.b.H. Nfg.KG, A-4866 Unterach, Austria) at 3 different timings of injections were compared. Dams received 2 intraperitoneal injections, 24 hours apart, commencing on day 7, 7.5, or 8. Fetuses were harvested on day 18. Anomalies were examined using a dissecting microscope and serial transverse sections.

RESULTS

Administering Adriamycin at 6 mg/kg on days 7 and 8 had the most teratogenic effect, with 80% of fetuses having 3 or more VACTERL anomalies: anorectal malformation, 100%; tracheoesophageal malformation, 50%; right-sided aortic arch, 58.3%; bladder agenesis/bilateral hydronephrosis, 100%.

CONCLUSION

This study establishes a mouse model that should provide insights into the cellular and molecular mechanisms underlying VACTERL anomalies.

Esophageal obstruction-prenatal detection rate and outcome

OBJECTIVE

Prenatal diagnosis of esophageal obstruction is believed to improve the outcome for the affected newborn. However, the prenatal detection rate is only 10-40%, the diagnosis is usually not made before the third trimester and the false-positive rate has been high. This study investigated the prenatal detection rate and time of prenatal diagnosis at our center and its influence on outcome. In addition, incidence, detection rate and accuracy of the diagnosis in a large non-selected population were determined.

METHODS

All cases diagnosed pre- or postnatally with esophageal obstruction and examined prenatally by ultrasound at the National Center for Fetal Medicine in Norway during 1987-2004 were evaluated.

RESULTS

Of 48 cases with esophageal obstruction, 21 (44%) were diagnosed prenatally (median, 32 + 0 weeks). All 21 had a small or empty stomach, 20/21 (95%) had polyhydramnios and 9/21 (43%) had a visible esophageal pouch. Associated anomalies were present in 38/48 cases (79%). The karyotype was abnormal in 11/48 cases (23%). Ten (21%) pregnancies with lethal fetal conditions were terminated. Two fetuses died in utero. Ten infants with associated anomalies died within 3 months after birth. The 26/48 (54%) survivors included 16/21 cases with a prenatal diagnosis of esophageal obstruction and 9/10 cases with isolated esophageal obstruction.

CONCLUSIONS

The clinical signs of polyhydramnios were the most important factors for prenatal detection of esophageal obstruction. Consequently, the time of diagnosis was late and the detection rate was low (44%). An increased awareness of the possibility of esophageal obstruction, leading to targeted examinations whenever the suspicion is raised during pregnancy, might improve the prenatal detection rate and thereby provide a possibility to improve the outcome. Of the cases with isolated esophageal obstruction, 90% survived, irrespective of prenatal diagnosis.

Adriamycin mouse model: a variable but reproducible model of tracheo-oesophageal malformations

A spectrum of tracheo-oesophageal malformations is seen in humans: oesophageal atresia, tracheal agenesis and laryngotracheo-oesophageal clefts. They are thought to share a common but unknown aetiology. These birth defects are frequently associated with other VACTERL anomalies. The adriamycin rat model (ARM) has proved to be a valuable model of the VACTERL anomalies, illustrating the dysmorphogenesis of oesophageal atresia and tracheal agenesis. As organogenesis relies on temporaspatially co-ordinated signalling systems, the next step would be to study the molecular pathogenesis of tracheo-oesophageal malformations. However, the mouse is the foremost mammal studied by developmental biologists, offering an expanding wealth of knowledge and scientific research techniques with which to investigate these anomalies. A limited dose response analysis of the teratogenicity of adriamycin in the mouse has identified a dose and timing of injections that produced tracheo-oesophageal malformations and other VACTERL anomalies. A clear account of the types and variability of the tracheo-oesophageal malformations produced by this dose is essential in order to be able to plan and interpret any future investigations of early gestation fetuses. CBA/Ca mice were accurately time-mated (n = 10). Nine dams received intraperitoneal injections of adriamycin (6 mg/kg) and one control dam received saline injections, on days 7 and 8. Fetuses were harvested on day 18, near term. Tracheo-oesophageal malformations were examined by dissecting microscope and serial transverse sections. Results are reported in the standard teratological manner as mean percentage per litter (+/-SEM). The resorption rate of the adriamycin treated fetuses was 50.4%. There were 29 adriamycin treated fetuses for inspection. Tracheo-oesophageal malformations were found in 29.2% (+/-10.3), affecting five out of nine litters. Oesophageal atresia occurred in 15.6% (+/-8.1), laryngotracheo-oesophageal cleft in 10.4% (+/-7) and tracheal agenesis in 3.1% (+/-3.1). All of these malformations occurred with a tracheo-oesophageal fistula. Unlike the ARM, the AMM can produce fetuses with complete laryngotracheo-oesophageal cleft as well as oesophageal atresia or tracheal agenesis. Their occurrence was found to be reproducible but variable. These are important considerations when planning and interpreting experiments using this model.

Anesthesia management of a patient with a laryngotracheo-esophageal cleft

Laryngotracheo-esophageal cleft is a rare congenital anomaly that results from complete or partial failure of the development of the tracheoesophageal septum. The presenting symptoms include stridor, respiratory distress, and coughing or cyanotic episodes with feeding. There are four classifications for laryngeal clefts; the severity depends on the type present. We discuss the anesthesia management of a neonate with a Type IV cleft who presented for an emergency gastric division to prevent pulmonary aspiration and later returned for final repair of the defect.

Abnormal separation of the respiratory primordium in the adriamycin mouse model of tracheoesophageal malformations

BACKGROUND/PURPOSE

Organogenesis relies on temperospatially coordinated signaling systems. The adriamycin rat model provided insights into the dysmorphogenesis of tracheoesophageal malformations. An adriamycin mouse model (AMM) would facilitate the investigation of their molecular pathogenesis. To transfer the knowledge gained from the rat, we describe a histological account of the critical period of organogenesis of these malformations in the AMM.

METHOD

CBA/Ca mice were accurately time-mated (n = 18). Dams received intraperitoneal injections of adriamycin (6 mg/kg) (n = 12) or saline control (n = 6) on days 7 and 8. Fetuses were harvested on days 9, 9.5, 10, 11, 12, and 13, resin embedded, and 1-mum sections of the developing foregut were examined.

RESULTS

Day 11 control fetuses showed normal separation of the respiratory primordium, with apoptotic bodies at the point of separation. A more caudal point of separation of the distal foregut without apoptotic bodies was found in 4 of 10 AMM fetuses. Day 13 AMM fetuses had dorsal or ventral outpouchings of the foregut, indicating which malformation they would develop. Abnormal branching of the notochord was seen from day 9.5 in AMM fetuses. This was not always associated with abnormal tracheoesophageal development.

CONCLUSION

This study confirms that the abnormal observations made in the rat model apply to the mouse.

Morphogenesis of the trachea and esophagus: current players and new roles for noggin and Bmps

The development of the anterior foregut of the mammalian embryo involves changes in the behavior of both the epithelial endoderm and the adjacent mesoderm. Morphogenetic processes that occur include the extrusion of midline notochord cells from the epithelial definitive endoderm, the folding of the endoderm into a foregut tube, and the subsequent separation of the foregut tube into trachea and esophagus. Defects in foregut morphogenesis underlie the constellation of human birth defects known as esophageal atresia (EA) and tracheoesophageal fistula (TEF). Here, we review what is known about the cellular events in foregut morphogenesis and the gene mutations associated with EA and TEF in mice and humans. We present new evidence that about 70% of mouse embryos homozygous null for Nog, the gene encoding noggin, a bone morphogenetic protein (Bmp) antagonist, have EA/TEF as well as defects in lung branching. This phenotype appears to correlate with abnormal morphogenesis of the notochord and defects in its separation from the definitive endoderm. The abnormalities in foregut and lung morphogenesis of Nog null mutant can be rescued by reducing the gene dose of Bmp4 by 50%. This suggests that normal foregut morphogenesis requires that the level of Bmp4 activity is carefully controlled by means of antagonists such as noggin. Several mechanisms are suggested for how Bmps normally function, including by regulating the intercellular adhesion and behavior of notochord and foregut endoderm cells. Future research must determine how Noggin/Bmp antagonism fits into the network of other factors known to regulate tracheal and esophagus development, both in mouse or humans.

CT of tracheal agenesis

BACKGROUND

Tracheal agenesis is a rare and usually lethal anomaly. In the past, opaque contrast medium was injected via the esophagus to demonstrate the anatomy.

OBJECTIVE

To demonstrate the utility of helical and multidetector CT in delineating the aberrant anatomy in newborns with tracheal agenesis.

MATERIALS AND METHODS

Four newborns with tracheal agenesis were identified from three institutions. Imaging studies and medical records were reviewed. Each child was imaged with chest radiography. One child was imaged on a single-detector helical CT scanner and the other three on multidetector scanners.

RESULTS

Helical and multidetector CT with 2D and 3D reconstructions clearly delineated the aberrant tracheobronchial and esophageal anatomy in each infant. Minimum intensity projection reformatted CT images were particularly helpful. One infant each had type I and type II tracheal agenesis. Two infants had type III tracheal agenesis. All four infants died.

CONCLUSION

CT is a useful tool for delineating the aberrant anatomy of newborns with tracheal agenesis and thus helps in making rational clinical decisions.

Tracheal atresia as part of an exceptional combination of malformations

A case of a premature infant with tracheal atresia together with an exceptional combination of congenital abnormalities that partially corresponds to the TACRD and VACTERL associations is presented. Tracheal atresia was not detectable in the prenatal ultrasound due to lacking of the typical diaphragmatic and pulmonary findings because of the esophago-tracheal fistula, and therefore the resuscitation team was not prepared for this severe airway complication. After prolonged resuscitation efforts were terminated and the newborn expired after birth. Even without typical warning signs physicians have to be aware of tracheal atresia and airway obstruction if VACTERL or TACRD associations are diagnosed.

Agenesis of the trachea: phenotypic expression of a rare cause of fatal neonatal respiratory insufficiency in six patients

Tracheal agenesis is a rare congenital malformation, which is usually fatal in the newborn period. Its incidence is approximately 1 in 50,000 births. Presentation is with respiratory insufficiency and no audible cry. Other anomalies are found in most cases. Six cases of tracheal agenesis were seen in our hospital since 1988. Their medical records were reviewed. Three of our cases classify as Floyd's type III, two as Floyd's type II and one as Floyd's type I. Associated anomalies were found in five cases. The classification of tracheal agenesis, associated anomalies and potential therapeutic options are discussed.

Decrease of parafollicular thyroid C-cells in experimental esophageal atresia: further evidence of a neural crest pathogenic pathway

Adriamycin-induced experimental esophageal atresia (EA) is often associated with malformations of neural crest (NC) origin, such as abnormal pharyngeal pouch derivatives like the thymus and the parathyroids. The aim of the present study was to examine whether NC-derived thyroid C-cells were abnormal in a rat model. Pregnant rats received intraperitoneally either 2 mg/kg Adriamycin (EA) or vehicle (controls) on days 8 and 9 of gestation. Fetuses were recovered on day 21, and blocks including the trachea and thyroid were fixed in formalin, coronally sectioned at 3-mum widths, and stained with standard hematoxylin and eosin until the largest area of thyroid was reached. From this point on, the 1st, 10th, and 20th slices were immunohistochemically stained with anti-calcitonin antibody. Positively-stained cells in each section of the gland were counted using a computer-assisted image analysis method, and the results were averaged. The distribution of the cells within the gland was assessed as well. Comparisons between EA and control rats were made by nonparametric tests with a significance threshold of p<0.05. The number of C-cells was dramatically reduced in EA animals compared with controls (32.4+/-36 vs. 92.3+/-60.5, p<0.001). Histology of the thyroid was similar in both groups, but the distribution of positive C-cells within the gland followed an abnormal pattern in EA rats. Adriamycin causes a pattern of NC-derived malformations, including a severe decrease in thyroid C-cells accompanied by abnormal distribution or migration patterns. These results represent further evidence of the involvement of NC organogenic control dysregulation in the pathogenesis of EA and its associated malformations. The similarities between the rat model and the clinical picture strongly support investigating other subclinical NC-derived anomalies in patients with EA.

Management and long-term follow-up of patients with types III and IV laryngotracheoesophageal clefts

BACKGROUND

Laryngotracheoesophageal cleft (LTEC) is a rare congenital anomaly that occurs when the trachea and esophagus fail to separate during fetal development. The 2 most severe forms of LTEC are type III, with extension of the cleft from the larynx to the carina, and type IV, with extension of the cleft into one or both mainstem bronchi.

METHODS

Over the past 25 years, we have accumulated an experience caring for 9 patients with severe LTEC, including 4 with type III and 5 with type IV.

RESULTS

Morbidity and mortality from severe LTEC often result from aspiration and chronic lung disease. Patients with types III (1/4) and IV (5/5) LTEC have an extremely high incidence of microgastria with a shortened esophagus for which fundoplication is ineffective. Because gastric feeding often does not initially increase stomach volume and may cause severe aspiration, we suggest early gastric division with later reconstruction of intestinal continuity in patients with microgastria. Postoperative tracheoesophageal fistulas have occurred in 6 of 9 patients.

CONCLUSIONS

Generous interposition of vascularized tissue with a multiple-layer closure has helped to prevent further recurrences. Postoperative tracheomalacia may be managed with continuous positive airway pressure and may require customized endotracheal tubes. Evaluation of respiratory and digestive function, school performance, and quality of life for the surviving patients is described.

Tracheal agenesis in newborns

OBJECTIVES/HYPOTHESIS

A series of three newborns with tracheal agenesis is described. The preferred methods of diagnosis, description of the clinical course, and a review of the pertinent embryology, associated anomalies, and clinical management are presented.

STUDY DESIGN

A retrospective study of a clinical series of referred patients from 2002 to 2003 who were seen at a single institution.

METHODS

Chart review for clinical course and pathological specimens was performed in all cases. Three patients were identified with tracheal agenesis.

RESULTS

All three newborns died within 48 hours of birth. All of the children underwent emergency laryngoscopy and neck exploration. Gross and microscopic pathological examination was accomplished on all patients.

CONCLUSION

Although tracheal agenesis is rare, it may be more common than previously thought. The diagnosis is not straightforward, and the prognosis is grim. The embryology of the trachea and other foregut derivatives is closely related, and associated birth defects are common.

Genetics and developmental biology of oesophageal atresia and tracheo-oesophageal fistula: lessons from mice relevant for paediatric surgeons

Oesophageal atresia and tracheo-oesophageal fistula are relatively frequently occurring foregut malformations of which the aetiology and pathogenesis are poorly understood. Recent results of molecular genetic studies, in particular the use of single and compound mutant mice, have yielded a tremendous increase in the understanding of the molecular mechanisms involved in normal and abnormal foregut morphogenesis. In the introduction of this paper, we review the very early stages of normal and abnormal embryology of the foregut derivatives and the separation of the foregut into a ventral respiratory part and a dorsal digestive part. After that, we describe the genes that have been demonstrated to play an important role in these processes.

Single umbilical artery and the VATER-animal model

BACKGROUND/PURPOSE

Vascular disruption is recognized as a cause of congenital malformations. The authors analyzed the significance of single umbilical artery (SUA) in the Adriamycin-animal model to find out if it was associated with organ malformations.

METHODS

Pregnant SD rats were injected with Adriamycin intraperitoneally at a dose of 2 mg/kg on days 6 through 9 of gestation. Serial transverse sections of full-term fetuses were analyzed by light microscopy. Embryos also were removed on different gestational days during organogenesis, and serial transverse histologic sections were examined and compared with suitable controls.

RESULTS

In experimental embryos (n = 47), presence of a SUA resulted from either persistence of the primitive umbilical arteries that joined each other ventral to the hind gut to give rise to one umbilical artery or from secondary atrophy of one of the definitive umbilical arteries. Malformations such as intestinal atresia were associated with anomalous fusion between the dorsal aorta and the persistent primitive umbilical arteries.

CONCLUSIONS

SUA is a prominent feature of the Adriamycin-animal model. No obvious association was found between malformations and SUA that resulted from atrophy of one of the definitive umbilical arteries; however, it was associated with anomalies such as intestinal atresia when it resulted from persistence of the primitive umbilical arteries.