Challenging embryological theories on congenital diaphragmatic hernia: future therapeutic implications for paediatric surgery

Fetal intervention for congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a condition that results from incomplete diaphragm formation during embryogenesis. The diaphragmatic defect allows for herniation of abdominal viscera into the chest, and the resulting pulmonary hypoplasia and pulmonary hypertension can lead to cardiorespiratory failure in the neonatal period. There is a wide spectrum of disease severity in CDH, and while advances in neonatal care and the introduction of extracorporeal membrane oxygenation have improved outcomes in many cases, the most severe defects are still associated with high morbidity and mortality. Improvements in prenatal diagnostic and prognostic capabilities have created an opportunity to select high risk patients for fetal intervention. Three decades of refinements in the fetal surgical therapy for CDH have led to the current technique of Fetoscopic Endoluminal Tracheal Occlusion (FETO). Herein, we review the current considerations for selecting patients for fetal intervention, and the contemporary fetal surgical operation for CDH, FETO, with a focus on early outcomes and ongoing studies.

Congenital asymptomatic diaphragmatic hernias in adults: a case series

INTRODUCTION

Congenital diaphragmatic hernia is a major malformation occasionally found in newborns and babies. Congenital diaphragmatic hernia is defined by the presence of an orifice in the diaphragm, more often to the left and posterolateral, that permits the herniation of abdominal contents into the thorax. The aim of this case series is to provide information on the presentation, diagnosis and outcome of three patients with late-presenting congenital diaphragmatic hernias. The diagnosis of congenital diaphragmatic hernia is based on clinical investigation and is confirmed by plain X-ray films and computed tomography scans.

CASE PRESENTATIONS

In the present report three cases of asymptomatic abdominal viscera herniation within the thorax are described. The first case concerns herniation of some loops of the large intestine into the left hemi-thorax in a 75-year-old Caucasian Italian woman. The second case concerns a rare type of herniation in the right side of the thorax of the right kidney with a part of the liver parenchyma in a 57-year-old Caucasian Italian woman. The third case concerns herniation of the stomach and bowel into the left side of the chest with compression of the left lung in a 32-year-old Caucasian Italian man. This type of hernia may appear later in life, because of concomitant respiratory or gastrointestinal disease, or it may be an incidental finding in asymptomatic adults, such as in the three cases featured here.

CONCLUSIONS

Patients who present with late diaphragmatic hernias complain of a wide variety of symptoms, and diagnosis may be difficult. Additional investigation and research appear necessary to better explain the development and progression of this type of disease.

Permissive hypercapnia in the management of congenital diaphragmatic hernia: our institutional experience

BACKGROUND

Congenital diaphragmatic hernia (CDH) is a potentially lethal anomaly associated with pulmonary hypoplasia and persistent pulmonary hypertension. Permissive hypercapnia is a strategy designed to reduce lung injury from mechanical ventilation in infants. It has been shown to be a potentially superior method of ventilator management for patients with CDH. In 2001, the Divisions of Neonatology and Pediatric Surgery at the University of Virginia Children's Hospital established permissive hypercapnia as the management strategy for treatment of CDH. We hypothesized that permissive hypercapnia would be associated with improved outcomes in this patient population.

STUDY DESIGN

This retrospective review compares outcomes of infants treated for CDH in the extracorporeal membrane oxygenation (ECMO) era before and after initiation of permissive hypercapnia at a single institution. Outcomes were compared using univariate statistical analysis.

RESULTS

Ninety-one patients were available for analysis and were divided into 2 groups: 42 (Group 1) treated before and 49 (Group 2) treated after implementation of permissive hypercapnia. Survival was higher in Group 2 (85.8% vs 54.8%; p = 0.001; relative risk [RR] 3.17). Morbidity was lower in Group 2 and approached statistical significance (65.3% vs 83.3%; p = 0.052). Patients in Group 2 were repaired later, had a lower rate of ECMO use, and were extubated earlier. There was no difference in hospital stay.

CONCLUSIONS

The use of permissive hypercapnia for infants with CDH was associated with decreased mortality, a longer period of ventilation before repair with a shorter period of ventilation after repair, a lower rate of ECMO use, and no lengthening of hospital stay. Permissive hypercapnia remains the standard of care for ventilation of infants with CDH at our institution.

[Congenital diaphragmatic hernia - mechanisms of pulmonary hypoplasia]

Congenital diaphragmatic hernia (CDH) is a common cause of severe neonatal respiratory distress. Mortality and morbidity are determined by the amount of pulmonary hypoplasia (PH) that occurs and by the development of therapy-resistant pulmonary hypertension. The pathogenesis and aetiology of CDH and its associated anomalies are still largely unknown despite all research efforts. The pathogenesis of CDH is based on an assumption linking herniation of abdominal viscera into the thorax with compression of the developing lung. PH, however, can also result from reduced distension of the developing lung secondary to impaired fetal breathing movements. Our understanding of CDH has also been aided by basic research with the use of dietary, teratogen-induced, and knockout models of CDH. These studies indicate that lung hypoplasia may involve disturbances of mitogenic signalling pathways fundamental to embryonic lung development. Recent data reveal the role of disruption of a retinoid-signalling pathway in the pathogenesis of CDH. Although multifactorial inheritance may best explain most cases of CDH in humans, much has been learned about the genetic factors that play a role in the development of CDH by studies of patients with CDH caused by specific genetic syndromes and chromosome anomalies. More research is warranted to improve our understanding of normal and abnormal lung development in relation to CDH. Such investigations will help in the design of new treatment strategies to improve the natural course or even to prevent this anomaly.

Heparan sulfate in lung morphogenesis: The elephant in the room

Heparan sulfate (HS) is a structurally complex polysaccharide located on the cell surface and in the extracellular matrix, where it participates in numerous biological processes through interactions with a vast number of regulatory proteins such as growth factors and morphogens. HS is crucial for lung development; disruption of HS synthesis in flies and mice results in a major aberration of airway branching, and in mice, it results in neonatal death as a consequence of malformed lungs and respiratory distress. Epithelial-mesenchymal interactions governing lung morphogenesis are directed by various diffusible proteins, many of which bind to, and are regulated by HS, including fibroblast growth factors, sonic hedgehog, and bone morphogenetic proteins. The majority of research into the molecular mechanisms underlying defective lung morphogenesis and pulmonary pathologies, such as bronchopulmonary dysplasia and pulmonary hypoplasia associated with congenital diaphragmatic hernia (CDH), has focused on abnormal protein expression. The potential contribution of HS to abnormalities of lung development has yet to be explored to any significant extent, which is somewhat surprising given the abnormal lung phenotype exhibited by mutant mice synthesizing abnormal HS. This review summarizes our current understanding of the role of HS and HS-binding proteins in lung morphogenesis and will present in vitro and in vivo evidence for the fundamental importance of HS in airway development. Finally, we will discuss the future possibility of HS-based therapeutics for ameliorating insufficient lung growth associated with lung diseases such as CDH.

Congenital diaphragmatic hernia: review of the literature in reflection of unresolved dilemmas

BACKGROUND

Congenital diaphragmatic hernia (CDH) is a rare but clinically and scientifically challenging condition. The introduction of ultrasound has enabled early prenatal detection and consequently, hope of early therapeutic intervention.

AIM

We undertook the task to review the recent developments in understanding the pathology of CDH as well as the history and current management strategies to aid perinatologists in consultations with parents of CDH-affected foetuses.

STUDY DESIGN

A Medline search was undertaken of all reports and reviews published between 1980 and 2008 using MeSH search terms 'diaphragmatic hernia', 'congenital' and 'newborn'.

RESULTS

The true incidence of CDH is still difficult to estimate because of the high incidence of hidden mortality of CDH. Complete case ascertainment also poses difficulties in assessment of the impact of new therapeutic modalities on overall survival. Recent improvements in prenatal detection are a milestone in affording time for re-assessments and parental counselling. The true benefit of antenatal therapy is circumscribed and should be offered only in selected cases of isolated severe CDH as defined by existing guidelines. Postnatal intensive respiratory supportive therapy and innovative surgical techniques within specialized tertiary centres has had a major impact on survival of babies with CDH.

CONCLUSION

The high survival of 'selected cases' that are live births and benefit from optimal care will be difficult to improve by antenatal interventions. The multidisciplinary approach to basic research and randomized clinical trials will further define the best approach to the foetus and neonate with CDH.

Exploiting mechanical stimuli to rescue growth of the hypoplastic lung

Impaired lung development afflicts a range of newborns cared for by paediatric surgeons. As a result the speciality has led in the development of surgical models that illustrate the biomechanical regulation of lung growth. Using transgenic mutants, biologists have similarly discovered much about the biochemical regulation of prenatal lung growth. Airway smooth muscle (ASM) and its prenatal contractility airway peristalsis (AP) represent a novel link between these areas: ASM progenitors produce an essential biochemical factor for lung morphogenesis, whilst calcium-driven biomechanical ASM activity appears to regulate the same. In this invited paper, I take the opportunity both to review our recent findings on lung growth and prenatal ASM, and also to discuss mechanisms by which ASM contractility can regulate growth. Finally, I will introduce some novel ideas for exploration: ASM contractility could help to schedule parturition (pulmonary parturition clock) and could even be a generic model for smooth muscle regulation of morphogenesis in similar organs.

Neonatal-onset nemaline myopathy mimicking congenital diaphragmatic hernia

In a newborn with severe respiratory failure and abnormal elevation of the right diaphragm, congenital diaphragmatic hernia with sac was diagnosed during surgery. However, microscopic examination of the sac showed atrophic striated muscle cells, indicating eventration instead of hernia. After several extubation failures, the final diagnosis of nemaline myopathy was made by skeletal muscle biopsy. In diaphragmatic defects with sac, diaphragm microscopic analysis should be recommended in order to discriminate between hernia and eventration. Congenital myopathies may underlie such diaphragmatic defects and should be promptly recognized, given their prognostic implications.

Prevention of heart failure in the management of congenital diaphragmatic hernia by maintaining ductal patency. A case report

Congenital diaphragmatic hernia is a rare entity in childhood carrying a high mortality rate of 30% to 50%. Ipsilateral pulmonary hypoplasia, increased pulmonary vascular resistance, and potential cardiac failure complicate early postnatal life. Surgical correction can either be performed on the first day of life or be deferred to a time after stabilization of the infant. Our patient presented with a left-sided Bochdalek's hernia containing large and small bowel. She required intubation and resuscitation on day 1 of life, and surgical repair had to be postponed. Further respiratory deterioration required commencement of inhaled nitric oxide and high-frequency ventilation. Pulmonary artery pressure rose to suprasystemic level. Closure of the ductus arteriosus on day 8 resulted in imminent right-sided heart failure. Commencement of alprostadil (prostaglandin E1) reopened the ductus and stabilized the patient. Surgical repair was successful 3 days later. Alprostadil should be considered as an important component of therapy in severe cases of congenital diaphragmatic hernia, where deterioration of right-sided heart function occurs.

Fetal lung growth in congenital diaphragmatic hernia

BACKGROUND

In spite of significant therapeutic progress, the prognosis of congenital diaphragmatic hernia (CDH) remains pejorative in those forms in which the liver is herniated into the chest. The severity of this malformation relies on the pulmonary hypoplasia due to lung compression by the herniated viscera in the thoracic cavity, particularly the liver. This impaired growth concerns the whole pulmonary tissue, i.e. both the vessels and the alveoli. For the clinician, it is mandatory to know the evolution pattern of the lesions, to define the best time to treat them.

AIM AND METHOD

The aim of this work was to study the pulmonary lesions along the gestation in fetuses affected byCDH. This morphological study was carried out on 134 human fetuses aged from 22 to 40 weeks of gestation. Anatomical and histological analysis focused on lung weight, alveolar count and wall thickness of the distal vessels.

RESULTS

The results indicate that the pulmonary lesions worsen as the pregnancy continues, particularly beyond 30 weeks of gestation.

CONCLUSION

Such an anatomical study should bring to the clinicians useful data to enhance the management of the patients.

Recent advances in congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a common birth defect which continues to challenge paediatric surgeons and intensivists. Affecting approximately 1:2500 births, a baby with CDH is born every 24-36 hours in the UK.

Fetal lung and diaphragm development in congenital diaphragmatic hernia

Congenital Diaphragmatic Hernia (CDH) is a congenital disorder with an incidence of 1 in 2500 live births. Respiratory distress of newborns with CDH is the result of pulmonary hypoplasia and pulmonary hypertension. Hypoplastic lungs are characterized by a decreased number of airways with smaller airspaces, whereas the combination of a decreased number of vascular branches and an increased adventitia and medial thickness of the pulmonary arterial walls result in pulmonary hypertension. The appearance of the CDH lungs suggests that its complete formation is stalled during development. Understanding the basic mechanisms of lung development is mandatory to unravel the origin of CDH. Although the histological abnormalities in CDH lungs have been well described, less is known about the underlying molecular mechanisms. In this review we will discuss the current molecular and genetic background of lung formation, as well as a reflection of this knowledge towards CDH.

Can maternal vitamin e supplementation prevent lung hypoplasia in the nitrofen-induced rat model of congenital diaphragmatic hernia?

Recent studies suggest a role for antioxidants in the prevention of pulmonary hypoplasia associated with congenital diaphragmatic hernia (CDH). We studied the effects of vitamin E in the nitrofen-rat model of CDH. After an initial fast, timed-pregnant Sprague-Dawley rats were gavage-fed nitrofen at gestational day 11 (term is 22 d). On the same day, one group was given a s.c. injection of vitamin E in alcohol; a second group was given an injection of alcohol alone. A third group received no treatment (control). Fetuses were delivered on day 21, and static pressure-volume curves were measured by immersion. Lungs were analyzed for total DNA and protein content by standard methods. A total of 203 fetuses were studied. Of 151 nitrofen-exposed fetuses, 77% had CDH; 92% of these were right-sided. CDH was present in 82% of vehicle-treated fetuses and 71% of vitamin E-treated fetuses (p=0.17). Nitrofen-exposed fetuses not only were smaller than control fetuses but also had disproportionately smaller lungs and poorer lung function, even when CDH was absent; however, lung function was worse when CDH was present. Vitamin E treatment did not improve either lung growth or function, although there was a trend toward less CDH. We have shown, for the first time, that the lung hypoplasia seen in nitrofen-exposed rat fetuses is associated with a dramatic reduction in static lung function, even when CDH is not present. Finally, our findings support the notion that lung hypoplasia in the nitrofen-rat model is independent of CDH formation.

The role of oxygen tension in the regulation of embryonic lung development

BACKGROUND/PURPOSE

Oxygen tension is an important physiologic mediator of embryonic and fetal development. In vitro studies have demonstrated that the proper embryonic development is dependent upon low oxygen tension and even short exposure to normoxic environments (21%) can be detrimental to embryonic development. We hypothesized that low oxygen tension promotes lung growth in embryonic organ culture and therefore designed this study to investigate embryonic lung growth in normoxic and hypoxic conditions using simple closed chamber.

METHODS

Fetal rat lungs were harvested on day 13.5 and placed in organ culture containing serum-free Dulbecco's modified Eagle's medium with antibiotics. The lung cultures were divided into normoxic group, with a 21% oxygen concentration (n = 15), and hypoxic group (n = 15). Hypoxic condition (6% oxygen) was achieved using Oxoid Campygen in a closed chamber. The lungs were placed in 5% carbon dioxide, 37 degrees C incubator for 48 hours. Media were not changed during the incubation period. The morphometric analysis was measured at 0 hour and at 48 hours by counting total terminal buds and entire epithelial contour using Image J software. The fold increase in branching was calculated as the ratio of buds present at 48 hours minus the buds present at 0 hour divided by the number of buds at 0 hour. The increase in entire epithelial contour over 48 hours was calculated in exactly the same way as described above.

RESULTS

There was no significant difference in the increase in total terminal buds count in the hypoxic group (2.06 +/- 0.19) compared with the normoxic group (2.59 +/- 0.21), and no significant difference in the increase in entire epithelial contour in the hypoxic group (1.45 +/- 0.11) compared with the normoxic group (1.63 +/- 0.11).

CONCLUSIONS

Although hypoxia has been reported to be an important regulator of murine vascular development, our data show that the embryonic lung growth in whole lung organ culture under hypoxic condition is not significantly different from that in normoxic condition.