The lungs in congenital bilateral renal agenesis and dysplasia

Elective Cesarean Section during Preterm Prevents Pulmonary Hypoplasia Development in Potter Sequence

Potter syndrome, first reported in 1946 by Edith Potter, refers to fatal cases of bilateral renal aplasia with pulmonary hypoplasia, peculiar facial features, and limb deformities. Presently, patients with oligohydramnios showing similar pathological manifestations due to oligohydramnios caused by conditions other than bilateral renal aplasia have been reported, and are known as the Potter sequence. There are limited studies and unclear guidelines on the safest delivery time and detailed postpartum management for patients with the Potter sequence. We experienced a case of Potter sequence, in which the patient was born by elective cesarean section at gestational age (GA) of 34 weeks. Fetal ultrasound at GA of 26 weeks 4 days showed oligohydramnios, multilocular cystic lesions in the left kidney, and an absent right kidney. Prenatal fetal MRI at GA of 33 weeks and 3 days showed pulmonary hypoplasia, and the ratio of fetal lung volume (FLV) to fetal body weight (FBW) was 0.0135 ml/g. We suspected that the fetal lung could not grow because of persistent oligohydramnios, which leads to a further decline in the ratio of FLV to FBW during pregnancy. We performed a cesarean section at GA of 34 weeks to prevent the exacerbation of the imbalance between lung volume and physique. We struggled to keep her condition stabilized with strict management of her respiratory condition, dialysis, and nutrition. She was discharged from the hospital at 169 days of age. Elective caesarean section in the term of premature birth prevented the progression of pulmonary hypoplasia and made it possible to save her life. Potter sequence is still relatively unknown, and it is necessary for more studies to be conducted in the future.

c-JUN-mediated transcriptional responses in lymphatic endothelial cells are required for lung fluid clearance at birth

Fluid clearance mediated by lymphatic vessels is known to be essential for lung inflation and gas-exchange function during the transition from prenatal to postnatal life, yet the molecular mechanisms that regulate lymphatic function remain unclear. Here, we profiled the molecular features of lymphatic endothelial cells (LECs) in embryonic and postnatal day (P) 0 lungs by single-cell RNA-sequencing analysis. We identified that the expression of c-JUN is transiently upregulated in P0 LECs. Conditional knockout of Jun in LECs impairs the opening of lung lymphatic vessels at birth, leading to fluid retention in the lungs and neonatal death. We further demonstrated that increased mechanical pressure induces the expression of c-JUN in LECs. c-JUN regulates the opening of lymphatic vessels by modulating the remodeling of the actin cytoskeleton in LECs. Our study established the essential regulatory function of c-JUN-mediated transcriptional responses in facilitating lung lymphatic fluid clearance at birth.

Fetal Therapy for Renal Anhydramnios

The most severe forms of congenital anomalies of the kidney and urinary tract present in fetal life with early pregnancy renal anhydramnios and are considered lethal due to pulmonary hypoplasia without fetal therapy. Due to the high rate of additional structural anomalies, genetic abnormalities, and associated syndromes, detailed anatomic survey and genetic testing are imperative when stratifying which pregnancies are appropriate for fetal intervention. Restoring amniotic fluid around the fetus is the principal goal of prenatal treatment. The ongoing multi-center Renal Anhydramnios Fetal Therapy (RAFT) trial is assessing the safety and efficacy of serial amnioinfusions to prevent pulmonary hypoplasia so that the underlying renal disease can be addressed.

Assessment of the fetal lungs in utero

Antenatal diagnosis of abnormal pulmonary development has improved significantly over recent years because of progress in imaging techniques. Two-dimensional ultrasound is the mainstay of investigation of pulmonary pathology during pregnancy, providing good prognostication in conditions such as congenital diaphragmatic hernia; however, it is less validated in other high-risk groups such as those with congenital pulmonary airway malformation or preterm premature rupture of membranes. Three-dimensional assessment of lung volume and size is now possible using ultrasound or magnetic resonance imaging; however, the use of these techniques is still limited because of unpredictable fetal motion, and such tools have also been inadequately validated in high-risk populations other than those with congenital diaphragmatic hernia. The advent of advanced, functional magnetic resonance imaging techniques such as diffusion and T2* imaging, and the development of postprocessing pipelines that facilitate motion correction, have enabled not only more accurate evaluation of pulmonary size, but also assessment of tissue microstructure and perfusion. In the future, fetal magnetic resonance imaging may have an increasing role in the prognostication of pulmonary abnormalities and in monitoring current and future antenatal therapies to enhance lung development. This review aims to examine the current imaging methods available for assessment of antenatal lung development and to outline possible future directions.

An atypical case of congenital lobar emphysema in an adult, non-smoker patient presenting with pneumothorax

Congenital lobar emphysema (CLE) is a developmental anomaly of the lower respiratory tract characterized by hyperinflation of one or more pulmonary lobes in the absence of extrinsic bronchial obstruction. We present a case of a 24-year-old male, nonsmoker who presented with shortness of breath and severe left sided chest pain. A chest x-ray was significant for a very large left-sided pneumothorax and chest CT showed lobar emphysematous changes. Video assisted thoracoscopic surgery (VATS) and lobectomy was subsequently performed after persistence of pneumothorax despite chest tube insertion and conservative management. Surgical pathology of resected specimen showed chronic emphysematous changes with patchy chronic organizing pneumonitis. Histology showed advanced emphysematous changes of pulmonary parenchyma consistent with congenital lobar emphysema. This finding combined with features seen on computed tomography of the chest led to the diagnosis of congenital lobar emphysema. This case demonstrated that CLE can be a cause of tension pneumothorax in adults in rare cases.

Fetal interventions for congenital renal anomalies

Congenital abnormalities of the kidney and urinary tract (CAKUT) represent 20% of prenatally diagnosed congenital abnormalities. Although the majority of these abnormalities do not require intervention either pre or postnatally, there is a subset of patients whose disease is so severe that it may warrant intervention prior to delivery to prevent morbidity and mortality. These cases consist of patients with moderate lower urinary tract obstruction (LUTO) in which vesicocentesis, shunting or cystoscopy are options and patients with early pregnancy renal anhydramnios (EPRA) in whom amnioinfusion therapy may be an option. The main causes of EPRA are congenital bilateral renal agenesis (CoBRA), cystic kidney disease (CKD) and severe LUTO. Untreated, EPRA is universally fatal secondary to anhydramnios induced pulmonary hypoplasia. The evidence regarding therapy for LUTO is limited and the stopped early PLUTO (Percutaneous Shunting in Lower Urinary Tract Obstruction) trial was unable to provide definitive answers about patient selection. Evidence for EPRA therapy is also scant. Serial amnioinfusions have shown promise in cases of EPRA due to CoBRA or renal failure and this treatment modality forms the basis of the ongoing NIH funded RAFT (Renal Anhydramnios Fetal Therapy) trial. At present, there is consensus that treatment for EPRA should only occur in the setting of a clinical trial.

Etiology and management of early pregnancy renal anhydramnios: Is there a place for serial amnioinfusions?

Early pregnancy renal anhydramios (EPRA) comprises congenital renal disease that results in fetal anhydramnios by 22 weeks of gestation. It occurs in over 1 in 2000 pregnancies and affects 1500 families in the US annually. EPRA was historically considered universally fatal due to associated pulmonary hypoplasia and neonatal respiratory failure. There are several etiologies of fetal renal failure that result in EPRA including bilateral renal agenesis, cystic kidney disease, and lower urinary tract obstruction. Appropriate sonographic evaluation is required to arrive at the appropriate urogenital diagnosis and to identify additional anomalies that allude to a specific genetic diagnosis. Genetic evaluation variably includes karyotype, microarray, targeted gene testing, panels, or whole exome sequencing depending on presentation. Patients receiving a fetal diagnosis of EPRA should be offered management options of pregnancy termination or perinatal palliative care, with the option of serial amnioinfusion therapy offered on a research basis. Preliminary data from case reports demonstrate an association between serial amnioinfusion therapy and short-term postnatal survival of EPRA, with excellent respiratory function in the neonatal period. A multicenter trial, the renal anhydramnios fetal therapy (RAFT) trial, is underway. We sought to review the initial diagnosis ultrasound findings, genetic etiologies, and current management options for EPRA.

Congenital lobar emphysema: Thoracotomy versus minimally invasive surgery

BACKGROUND:

Congenital lobar emphysema (CLE) is a rare developmental malformation of the lung but can be associated with high morbidity and mortality. The objective of this study is to review our experience with 45 patients with CLE highlighting clinical features, aspects of diagnosis, and management.

METHODS:

The medical records of all patients diagnosed with CLE in our center were reviewed. Patients age at the time of diagnosis, sex, clinical presentation, associated anomalies, the lobes affected, treatment modality, and outcome were described. A comparison was made between those who had lobectomy via open thoracotomy and those treated thoracoscopically.

RESULTS:

From January 2000 to December 2018, a total of 45 infants with CLE were presented to our institution. There were 30 male and 15 female, and the mean age at presentation was 3.35 months. Twenty-five patients presented with respiratory distress. Nine patients presented immediately after birth, and two of them had surgery within the 1^st week of life. Twenty patients were presented with repeated chest infections. Left upper lobe was affected in 27 patients, right middle lobe in 13, and right upper lobe in 5 patients. Forty-four patients had a lobectomy, and one was managed conservatively. One patient had a postoperative bronchopleural fistula. Nine patients had a thoracoscopic lobectomy, and two of them were converted to open thoracotomy because of persistent air leak. The operative time and hospital stay were nonsignificantly longer in thoracoscopic lobectomy (P = 0.5 and 0.4, respectively). There was no operative mortality in both groups.

CONCLUSIONS:

CLE is a rare malformation with variable presentation. Infants presenting with respiratory distress or recurrent chest infection should be evaluated for the possibility of CLE. Lobectomy is the treatment of choice, and rarely, the patients may be managed conservatively. Thoracoscopic lobectomy is a safe procedure with the possibility of air leak and conversion to open lobectomy.

Two infants with bilateral renal agenesis who were bridged by chronic peritoneal dialysis to kidney transplantation

Bilateral renal agenesis is associated with severe oligohydramnios and was considered incompatible with postnatal life due to severe pulmonary hypoplasia. The use of renal replacement therapy was limited by significant morbidity and mortality associated with dialysis in very young infants with major pulmonary pathology. In the United States, there is a tremendous controversy about whether or not the use of prenatal amniotic fluid infusions provides a benefit to fetuses with bilateral renal agenesis. One of the critical issues identified is that there are, as yet, no children reported who had achieved long-term survival. Previous reports all indicated these children died shortly after birth or after unsuccessful peritoneal dialysis. We present two infants with a prenatal diagnosis of bilateral renal agenesis whose mothers elected to undergo prenatal amnioinfusions. One was born at 28 weeks with a birthweight of 1230 g and the other born at 34 weeks with a birthweight of 1940 g. We present the details of both cases, with initial management on chronic peritoneal dialysis, which started shortly after birth, as a bridge to living related kidney transplants.

Amnioinfusions to Treat Early Onset Anhydramnios Caused by Renal Anomalies: Background and Rationale for the Renal Anhydramnios Fetal Therapy Trial

Anhydramnios caused by early anuria is thought to be universally fatal due to pulmonary hypoplasia. Bilateral renal agenesis and early fetal renal failure leading to anhydramnios constitute early pregnancy renal anhydramnios (EPRA). There have been successful reports of amnioinfusions to promote lung growth in the setting of EPRA. Some of these successfully treated EPRA fetuses have survived the neonatal period, undergone successful dialysis, and subsequently received a kidney transplant. Conversely, there are no reports of untreated EPRA survivors. This early success of amnioinfusions to treat EPRA justifies a rigorous prospective trial. The objective of this study is to provide a review of what is known about fetal therapy for EPRA and describe the Renal Anhydramnios Fetal Therapy trial. We review the epidemiology, pathophysiology, and genetics of EPRA. Furthermore, we have performed systematic review of case reports of treated EPRA. We describe the ethical framework, logistical challenges, and rationale for the current single center (NCT03101891) and planned multicenter trial.

A splice site variant in INPP5E causes diffuse cystic renal dysplasia and hepatic fibrosis in dogs

Ciliopathies presenting as inherited hepatorenal fibrocystic disorders are rare in humans and in dogs. We describe here a novel lethal ciliopathy in Norwich Terrier puppies that was diagnosed at necropsy and characterized as diffuse cystic renal disease and hepatic fibrosis. The histopathological findings were typical for cystic renal dysplasia in which the cysts were located in the straight portion of the proximal tubule, and thin descending and ascending limbs of Henle’s loop. The pedigree of the affected puppies was suggestive of an autosomal recessive inheritance and therefore, whole exome sequencing and homozygosity mapping were used for identification of the causative variant. The analyses revealed a case-specific homozygous splice donor site variant in a cilia related gene, INPP5E: c.1572+5G>A. Association of the variant with the defect was validated in a large cohort of Norwich Terriers with 3 cases and 480 controls, the carrier frequency being 6%. We observed that the identified variant introduces a novel splice site in INPP5E causing a frameshift and formation of a premature stop codon. In conclusion, our results suggest that the INPP5E: c.1572+5G>A variant is causal for the ciliopathy in Norwich Terriers. Therefore, genetic testing can be carried out in the future for the eradication of the disease from the breed.

Autosomal recessive polycystic kidney disease (ARPKD) in a Nigerian newborn: a case report

Autosomal recessive polycystic kidney disease (ARPKD) is a rare genetic disorder but even rarer in Africans and it is one of the causes of nephropathies in childhood. Although isolated cases of adult PKD have been reported in Nigerians; to the best of our knowledge, this case is the first to be reported in the paediatric age group in Nigeria. A case of autosomal recessive polycystic kidney disease presenting with severe perinatal asphyxia and severe respiratory distressis here by presented. Fetal ultrasonography during the pregnancy missed the diagnosis. The difficulty in making diagnosis and management is discussed. Autopsy helped to unravel the diagnosis in this case report.

Kidney-lung connections in acute and chronic diseases: current perspectives

Lung and kidney functions are intimately related in both health and disease. The regulation of acid-base equilibrium, modification of partial pressure of carbon dioxide and bicarbonate concentration, and the control of blood pressure and fluid homeostasis all closely depend on renal and pulmonary activities. These interactions begin in fetal age and are often responsible for the genesis and progression of diseases. In gestational age, urine is a fundamental component of the amniotic fluid, acting on pulmonary maturation and growth. Moreover, in the first trimester of pregnancy, kidney is the main source of proline, contributing to collagen synthesis and lung parenchyma maturation. Pathologically speaking, the kidneys could become damaged by mediators of inflammation or immuno-mediated factors related to a primary lung pathology or, on the contrary, it could be the renal disease that determines a consecutive pulmonary damage. Furthermore, non immunological mechanisms are frequently involved in renal and pulmonary diseases, as observed in chronic pathologies such as sleep apnea syndrome, pulmonary hypertension, progressive renal disease and hemodialysis. Kidney damage has also been related to mechanical ventilation. The aim of this review is to describe pulmonary-renal interactions and their related pathologies, underscoring the need for a close collaboration between intensivists, pneumologists and nephrologists.

Renal tubular dysgenesis with atypical histology andin-uteroexposure to naproxen sodium

Renal tubular dysgenesis (RTD), a rare, lethal, autosomal recessive disorder, is characterised by short and poorly differentiated proximal convoluted tubules associated with oligohydramnios, Potter sequence and neonatal death from respiratory failure. We report an unusual case of neonatal anuria owing to RTD with normally formed lungs, in-utero exposure to naproxen sodium and atypical histology in that the glomeruli were not as crowded as usually seen in RTD. When there is anuria in an infant following birth in the context of a normal renal ultrasound and an absence of objective evidence of perinatal hypoxia, RTD should be considered.

Type 2 congenital pulmonary airway malformation and congenital nephrotic syndrome: report of a new association

Type 2 congenital pulmonary airway malformation (CPAM) has been reported in association with many other congenital anomalies. To the best of our knowledge, however, an association of type 2 CPAM with congenital nephrotic syndrome has not been heretofore reported. We present the 1st report of such an association in a boy who had a prenatal diagnosis of cystic lung malformation and was found to have congenital nephrotic syndrome (diffuse mesangial sclerosis) at 1 month of age. A prenatal ultrasonogram had also shown oligohydramnios, and additionally the child had cleft lip and palate. There was no family history of childhood renal or pulmonary disease, and genetic testing for genes mutated in congenital nephrotic syndrome was negative.

Premature differentiation of vascular smooth muscle cells in human congenital diaphragmatic hernia

BACKGROUND

Congenital diaphragmatic hernia (CDH) is a rare congenital anomaly characterized by the herniation of abdominal organs into the chest cavity. The high mortality and morbidity of CDH patients are primarily caused by the associated pulmonary hypertension (PH), characterized by the thickening of the vascular media and adventitia. The media consist of heterogeneous populations of vascular smooth muscle cells (VSMC), ranging from synthetic to the characteristic contractile cells. VSMCs are influenced by developmental and environmental cues and may play a role in the development of the structural changes observed in CDH patients. Therefore, we hypothesized that the distribution of the VSMC populations may already be different at the origin of CDH development.

METHODOLOGY

We analyzed the protein expression of specific markers associated with synthetic and contractile VSMC phenotypes in human lungs at different developmental stages. Next, we compared lungs of premature and term CDH patients, as well as patients with lung hypoplasia due to renal agenesis or PROM, with age-matched controls.

RESULTS

Synthetic and contractile VSMCs are distributed in a temporal and spatial specific pattern along the proximodistal axis of the lung. CDH patients have more abundant contractile VSMCs which are also more distally distributed. This different distribution pattern is already observed from 19 weeks of gestation onwards.

CONCLUSION

Our data suggest that the more extensive distribution of contractile VSMCs is associated with an early maturation of the pulmonary vasculature, contrasting the concept that CDH might be the result of delayed maturation of the epithelium.

Pulmonary complications of renal disorders

To manage patients with diseases of the lungs and the kidneys, one must first understand the relationship between respiratory and renal function. In treating acute renal failure (ARF), the clinician often must contend with respiratory manifestations of volume overload and metabolic acidosis. Mechanical ventilation in patients with renal failure (RF) can be challenging, particularly with lung protective ventilation and weaning. Patients with chronic renal failure (CRF) experience several respiratory complications. Hypoxaemia during dialysis is now understood to be a predictable effect of the loss of CO(2) into the dialysate. Critical illness of any primary cause predisposes patients not only to acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) but also to the development of ARF. Meanwhile, the potential for ventilator-induced renal injury has increasingly become the subject of active investigation.

Vascular abnormalities in human newborns with pulmonary hypertension

Pulmonary vascular disease embodies all congenital or acquired pathologies that affect the pulmonary vasculature. One of them is pulmonary hypertension of the newborn (PHN), which is clinically characterized by a persistent high pulmonary vascular resistance postnatally and an abnormal vascular response. Morphologically, the vascular walls of the small pulmonary arteries become thickened, leading to increased resistance of these vessels and thus a worsening of gas exchange. PHN occurs as a primary disease or in association with abnormal lung development, for example as in congenital diaphragmatic hernia, and is a critical determinant of morbidity and mortality. Here we review the current knowledge about vascular abnormalities in PHN and discuss the vascular abnormalities in different conditions associated with pulmonary hypertension in human newborns in relation to recent findings from molecular biology.

Prenatal diagnosis of primary pulmonary hypoplasia in fraternal twins

Primary pulmonary hypoplasia is a rare, usually lethal, condition presenting only after birth without other congenital abnormalities. We describe the first case of fraternal twins diagnosed prenatally with primary pulmonary hypoplasia. Both had diffuse hypoplasia of the pulmonary arteries initially identified by fetal echocardiography and confirmed at autopsy following termination. These cases permit examination of the histopathology of this disease in the fetal stage of development.

Oligohydramnios and associated fetal complications

During intrauterine life the fetus is bathed in amniotic fluid which provides a low resistance space for free movement and a buffer against external trauma. This fluid is produced in early pregnancy largely as a maternal dialysate, then as a fetal transudate. Fetal urine is the most important source of amniotic fluid after 16 weeks gestation. The control of amniotic fluid is complex and poorly understood; it arises from secondary partitioning of water within the fetoplacental extracellular space and reflects fetal fluid balance.

Development of the fetal lung

The development of the fetal lung compared to that of other organs is unusual in the degree of its dependence on extrinsic stimuli. When the space available to the growing lung is limited by space-occupying lesions or when the diaphragm is paralysed, lung growth is markedly impaired. The relationship of lung volume to growth may depend on lung distension. Lung hypoplasia associated with experimental procedures causing inhibition or blunting of fetal breathing movements suggests that the distending forces may be generated by these movements. Maturation is less dependent on distension and more dependent on the hormonal environment. Distensibility and stability of the lung in fetal sheep develops rapidly within a few days of birth and correlates strongly with the plasma cortisol concentration. Hypophysectomy retards mutation which is restored by infusing adrenocorticotropin but not cortisol into the fetus. The hormones mainly responsible for controlling the various aspects of maturation probably include cortisol, iodothyronines and catecholamines but the interrelationships of these hormones and the extent of involvement of other hormones is uncertain.

Developmental regulation of lumenal lung fluid and electrolyte transport

In the fetus, there is a net secretion of liquid (LL) by the lung as a result of active transport of chloride ions. The rate of secretion and the resulting volume of LL are vital for normal lung growth but how volume is sensed and how secretion may be regulated are still unknown. Towards term under the influence of thyroid and adrenocorticoid hormones, the epithelial sodium channel (ENaC) is increasingly expressed in the pulmonary epithelium. Adrenaline released by the fetus during labour activates ENaC and produces rapid absorption of liquid in preparation for air breathing; absence of ENaC is incompatible with survival. There may be other mechanisms involved in aiding liquid clearance including changes in epithelial permeability, an effect of oxygen on both ENaC and Na/K ATPase and perhaps the influence of additional hormones on ENaC activity. Some time after birth there are further developmental changes with the appearance of other cation channels (CNG1 and perhaps NSCC) which contribute to the liquid absorptive side of the balance existing across the epithelium between secretion and absorption to produce essentially almost no net liquid movement in the postnatal lung. The evidence for these processes is discussed and areas of uncertainty indicated.

The Respiratory System

One of the most critical events of birth is the conversion of the fluid-filled lung, unimportant to fetal intrauterine existence, into a hollow organ distended with air and capable of gaseous exchange sufficient to support life. Indeed, it has been argued that the major determinant of perinatal survival is respiratory function (Wigglesworth and Desai 1982).

The failure to make this conversion adequately may lead, directly or indirectly, to infant death, and the pathologist often needs to assess the contribution made by respiratory inadequacy to the sequence of events leading to death. In the preterm infant, problems are mainly related to pulmonary immaturity and associated therapy. In the mature infant, birth asphyxia primarily results in cerebral damage but can engender significant respiratory complications when associated with aspiration of meconium. Even in stillbirths, where primary pulmonary pathology is rarely a cause of death, lung pathology may provide clues to antecedent events. Poor lung growth and maturation may point to the presence of pathology elsewhere. Consequently, adequate pathological investigation of the fetal or infant respiratory system is critical in any perinatal autopsy.

Molecular mechanisms of pulmonary vascular development

In this era of rapidly advancing vascular biology research, a vast array of growth factors and signaling molecules have been recognized as key players in the mechanisms that control lung vascular development. In the lung, vascular development is a complex, multistep process that includes specialization of primitive cells to vascular progenitors; formation of primitive vascular networks; remodeling with local regression and branching; specialization toward arteries, veins, and lymphatics; stabilization of vessels by matrix production and recruitment of supporting cells; and maintenance of the vascular structure. This complex, highly organized process requires exquisite orchestration of the regulatory activity of multiple molecules in a specific temporospatial order. Most of these molecules are members of 3 major growth factor families that have been recently identified. They are the vascular endothelial growth factor, angiopoietin, and ephrin families. Understanding the functional reach of several members of these growth factor families is integral to an appreciation of the etiology and pathogenesis of developmental lung vascular disorders affecting newborns. This review summarizes recent advances in the molecular bases of lung vascular development and some of the pulmonary diseases resulting from aberrant vascular growth, including bronchopulmonary dysplasia, alveolar capillary dysplasia, congenital cystic pulmonary disorders, congenital pulmonary hemangiomatosis, and lung hypoplasia.

Chronic effects of mechanical force on airways

Airways are embedded in the mechanically dynamic environment of the lung. In utero, this mechanical environment is defined largely by fluid secretion into the developing airway lumen. Clinical, whole lung, and cellular studies demonstrate pivotal roles for mechanical distention in airway morphogenesis and cellular behavior during lung development. In the adult lung, the mechanical environment is defined by a dynamic balance of surface, tissue, and muscle forces. Diseases of the airways modulate both the mechanical stresses to which the airways are exposed as well as the structure and mechanical behavior of the airways. For instance, in asthma, activation of airway smooth muscle abruptly changes the airway size and stress state within the airway wall; asthma also results in profound remodeling of the airway wall. Data now demonstrate that airway epithelial cells, smooth muscle cells, and fibroblasts respond to their mechanical environment. A prominent role has been identified for the epithelium in transducing mechanical stresses, and in both the fetal and mature airways, epithelial cells interact with mesenchymal cells to coordinate remodeling of tissue architecture in response to the mechanical environment.

Pulmonary hypoplasia in a 52-year-old woman

Pulmonary hypoplasia is a bronchopulmonary foregut anomaly characterized by a decreased number of alveoli and decreased alveolar air space. At autopsy, pulmonary hypoplasia is one of the important causes of death in newborns and infants. Pulmonary hypoplasia is rare in adults. In this paper, we present a case of pulmonary hypoplasia in a 52-year-old, asymptomatic woman. We discuss pulmonary hypoplasia and review the literature findings.

Sinusoidal heart rate pattern: Reappraisal of its definition and clinical significance

OBJECTIVES

To address the clinical significance of sinusoidal heart rate (SHR) pattern and review its occurrence, define its characteristics, and explain its physiopathology.

BACKGROUND

In 1972, Manseau et al. and Kubli et al. described an undulating wave form alternating with a flat or smooth baseline fetal heart rate (FHR) in severely affected, Rh-sensitized and dying fetuses. This FHR pattern was called 'sinusoidal' because of its sine waveform. Subsequently, Modanlou et al. described SHR pattern associated with fetal to maternal hemorrhage causing severe fetal anemia and hydrops fetalis. Both Manseau et al. and Kubli et al. stated that this particular FHR pattern, whatever its pathogenesis, was an extremely significant finding that implied severe fetal jeopardy and impending fetal death. UNDULATING FHR PATTERN: Undulating FHR pattern may be due to the following: (1) true SHR pattern; (2) drugs; (3) pre-mortem FHR pattern; (4) pseudo-SHR pattern; and (5) equivocal FHR patterns. FETAL CONDITIONS ASSOCIATED WITH SHR PATTERN: SHR pattern has been reported with the following fetal conditions: (1) severe fetal anemia of several etiologies; (2) effects of drugs, particularly narcotics; (3) fetal asphyxia/hypoxia; (4) fetal infection; (5) fetal cardiac anomalies; (6) fetal sleep cycles; and (7) sucking and rhythmic movements of fetal mouth. DEFINITION OF TRUE SHR PATTERN: Modanlou and Freeman proposed the following definition for the interpretation of true SHR pattern: (a) stable baseline FHR of 120-160 bpm; (b) amplitude of 5-15 bpm, rarely greater; (c) frequency of 2-5 cycles per minute; (d) fixed or flat short-term variability; (e) oscillation of the sinusoidal wave from above and below a baseline; and (f) no areas of normal FHR variability or reactivity.

PHYSIOPATHOLOGY

Since its early recognition, the physiopathology of SHR became a matter of debate. Murata et al. noted a rise of arginine vasopressin levels in the blood of posthemorrhagic/anemic fetal lamb. Further works by the same authors revealed that with chemical or surgical vagotomy, arginine vasopressin infusion produced SHR pattern, thus providing the role of autonomic nervous system dysfunction combined with the increase in arginine vasopressin as the etiology.

CONCLUSION

SHR is a rare occurrence. A true SHR is an ominous sign of fetal jeopardy needing immediate intervention. The correct diagnosis of true SHR pattern should also include fetal biophysical profile and the absence of drugs such as narcotics.

Developmental Regulation of Lung Liquid Transport

The developing distal lung epithelium displays an evolving liquid transport phenotype, reflecting a changing and dynamic balance between Cl- ion secretion and Na+ ion absorption, which in turn reflects changing functional requirements. Thus in the fetus, Cl--driven liquid secretion predominates throughout gestation and generates a distending pressure to stretch the lung and stimulate growth. Increasing Na+ absorptive capacity develops toward term, anticipating the switch to an absorptive phenotype at birth and beyond. There is some empirical evidence of ligand-gated regulation of Cl- transport and of regulation via changes in the driving force for Cl- secretion. Epinephrine, O2, glucocorticoid, and thyroid hormones interact to stimulate Na+ absorption by increasing Na+ pump activity and apical Na+ conductance (GNa+) to bring about the switch from net secretion to net absorption as lung liquid is cleared from the lung at birth. Postnatally, the lung lumen contains a small Cl--based liquid secretion that generates a surface liquid layer, but the lung retains a large absorptive capacity to prevent alveolar flooding and clear edema fluid. This review explores the mechanisms underlying the functional development of the lung epithelium and draws upon evidence from classic integrative physiological studies combined with molecular physiology approaches.

Renal tubular dysgenesis and neonatal hemochromatosis without pulmonary hypoplasia

Renal tubular dysgenesis is a rare disorder of differentiation of the fetal kidney. The condition has previously been reported as a postmortem diagnosis in infants who have had oligohydramnios commencing after 20 weeks gestation and have died of renal or respiratory failure shortly after birth with a clinical description of Potter sequence. The absence of clinically significant pulmonary hypoplasia in our case serves to emphasize that renal tubular dysgenesis, fetal anuria and long-standing oligohydramnios can occur without pulmonary insufficiency. The coexistence of renal tubular dysgenesis with neonatal hemochromatosis has been previously described in four published cases. The link between these two rare conditions is clinically important if dialysis or liver transplantation is considered in infants with hepatic and renal failure. Antemortem diagnosis by renal biopsy in our case enabled parental counseling and avoided the inappropriate use of peritoneal dialysis.

Pulmonary hypoplasia with an unusual prenatal history

We describe a monochorionic, diamniotic twin with renal agenesis who received amniotic fluid from his normal co-twin by spontaneous rupture of the amniotic septum between them. By 16 weeks of gestation the presence of severe oligohydramnios in one twin had resulted in renal agenesis, but not in the other twin, who did not have oligohydramnios. By 20 weeks of gestation, the two amniotic fluid volumes had become the same in both twins. At 33 weeks, the twins were delivered by cesarean section. Despite intensive respiratory care, the twin with renal agenesis died from severe pneumomediastinum on day 3. At autopsy, pulmonary hypoplasia was demonstrated in that twin. This experiment of nature demonstrates that oligohydramnios during the early canalicular stage of pulmonary development (gestational age, 16-20 weeks) may be pathogenically important in pulmonary hypoplasia.

Prenatal prediction of pulmonary hypoplasia: clinical, biometric, and Doppler velocity correlates

OBJECTIVES

To determine the value of pulmonary artery Doppler velocimetry relative to fetal biometric indices and clinical correlates in the prenatal prediction of lethal lung hypoplasia (LH) in prolonged (>1 week) oligohydramnios.

METHODS

Forty-two singleton pregnancies with oligohydramnios associated with premature rupture of membranes ([PROM]; n = 31) or bilateral renal pathology (n = 11) were examined using color-coded Doppler ultrasound in a cross-sectional study design. Mean gestational age was 28.0 +/- 4.3 weeks (range: 20-36 weeks). Thoracic, cardiac, and abdominal circumference and the largest vertical amniotic fluid pocket were measured. Pulsed Doppler measurements of the arterial pulmonary branches were made at the level of the cardiac 4-chamber view. Diagnosis of LH was based on clinical, radiologic, and pathologic criteria. Clinicians were blinded to the prenatal measurements.

RESULTS

The prevalence of lethal LH was 43%. In the PROM subset, combination of onset of PROM at <or =20 weeks, duration of oligohydramnios at > or =8 weeks, and degree of oligohydramnios at < or =1 cm presented the highest clinical prediction rate for lethal LH. For both the total group and the PROM subset, the highest prediction rate for lethal LH was presented by thoracic circumference/abdominal circumference ratio, peak systolic velocity in the proximal branch, and time-averaged and end-diastolic velocity in the middle branch of the pulmonary artery. In the PROM subset, the combination of all 3 clinical, biometric, and Doppler parameters revealed the most favorable combination to predict lethal LH (positive predictive value: 100%; accuracy: 93%; and sensitivity: 71%).

CONCLUSION

Doppler velocimetry may detect changes in pulmonary artery waveforms in the presence of LH but fails to be the ultimate test for the prenatal prediction of lethal LH. The best prediction can be achieved by combining clinical, biometric, and Doppler parameters.

The fetal lung. 2: Pulmonary hypoplasia

This review describes the pathogenesis of pulmonary hypoplasia and highlights its clinical, radiological and pathologic features, with emphasis on oligohydramnios-related pulmonary hypoplasia. Since pulmonary hypoplasia may lead to severe respiratory distress immediately after birth and even to neonatal death, an accurate and patient-friendly prenatal test for early detection and distinction between lethal and non-lethal pulmonary hypoplasia is still highly desirable. An extended overview of the proposed methods for the prenatal prediction of pulmonary hypoplasia is presented.

Pulmonary hypoplasia induced by liquid paraffin injection into fetal thoracic cavity with special reference to renal development in rats

The present study was designed to clarify lung-kidney interrelation in fetal rats. On fetal day 20, liquid paraffin (LP) was injected into fetal thoracic cavity to produce pulmonary hypoplasia. No significant difference in body and renal weights were noted between the LP injected and control fetuses. The weight of lung, however, was significantly lower in the LP injected fetuses than in the control ones. Histological examinations on the lung and kidney of the LP injected fetuses revealed that the lung was hypoplastic characterized by rich interstitium and reduced air spaces. In the kidney, mature types of glomeruli and profiles of proximal tubules near them were increased in number. Furthermore, strong expression of EGF immunoreactivity was noted in the apical cytoplasm of epithelium of the proximal tubules in the LP injected fetuses. These findings indicate that lung-kidney interrelation exists in fetal rats during late gestational days, and suggest that interruption of the lung development induces accelerated growth of the kidney in fetal rats.

Human pulmonary acinar aplasia: reduction of transforming growth factor-beta ligands and receptors

Pulmonary hypoplasia has been found in the human neonatal autopsy population and has been attributed to an alteration in epithelial-mesenchymal interactions during development of the lung. Pulmonary acinar aplasia is a very rare and severe form of pulmonary hypoplasia. The transforming growth factor-betas (TGF-beta) are multifunctional regulatory peptides that are secreted by a variety of normal and malignant cells and are expressed in developing organs including the lung; their tissue distribution patterns have possible significance for signaling roles in many epithelial-mesenchymal interactions. Here, we report our examination of TGF-beta in the lungs of a term female infant diagnosed with pulmonary acinar aplasia whose autopsy revealed extremely hypoplastic lungs with complete absence of alveolar ducts and alveoli. Immunohistochemical and in situ hybridization analyses were used to localize and measure the proteins and mRNA, respectively, for TGF-beta1, TGF-beta2, TGF-beta3, and TGF-beta type I and type II receptors (TGF-beta RI and RII) in formalin-fixed and paraffin-embedded sections of these hypoplastic lungs and normal lungs. Immunostaining for TGF-beta1, TGF-beta2, and TGF-beta RI and RII was significantly lower in the bronchial epithelium and muscle of the hypoplastic lungs than in normal lungs, whereas no difference was detected in staining for other proteins including Clara cell 10-kD protein, adrenomedullin, hepatocyte growth factor/scatter factor, and hepatocyte growth factor receptor/Met in the hypoplastic and normal lungs or in the liver and kidneys of this infant compared with normal liver and kidney. In addition, in situ hybridization showed that TGF-beta1 and TGF-beta RI transcripts were considerably reduced in the bronchial epithelium of the hypoplastic lung compared with normal lung. These results show that there is a selective reduction of TGF-beta in pulmonary acinar aplasia and suggest that the signaling action of TGF-beta in epithelial-mesenchymal interactions in the lungs of this developmental condition may be compromised.

Pulmonary arterial Doppler velocimetry in fetuses with lung hypoplasia

OBJECTIVE

The aim of the study was to examine Doppler flow velocity waveforms in the main stems of the pulmonary arteries in fetuses with autopsy-proven lung hypoplasia and to find out whether in these conditions typical patterns can be found.

STUDY DESIGN

Doppler spectra were derived from the main stem of the right or left pulmonary artery in fetuses at high-risk for lung-hypoplasia. The following Doppler parameters were analyzed and compared to reference ranges: peak systolic velocity, acceleration time, time velocity integral, end-systolic reverse flow, pulsatility index (PI). Pulmonary hypoplasia was found in nine cases at autopsy after termination of pregnancy (19-23 weeks). According to etiology, three groups were considered: (A) bilateral renal malformations (n=4), (B) congenital diaphragmatic hernia (n=2), and (C) miscellaneous malformations including heart defects (n=3).

RESULTS

The following Doppler parameters were found: normal values in end-systolic reversal flow in all cases, decreased peak systolic velocity and acceleration time in 3/9, decreased time velocity integral in 4/9 and increased pulsatility index in 6/9. Considering the etiology of pulmonary hypoplasia the pulsatility index was found to be the most sensitive, since all fetuses in groups A and B had an abnormal PI.

CONCLUSIONS

Human fetuses with renal malformations and diaphragmatic hernia associated with lung hypoplasia show as early as 19-23 weeks of gestation an abnormal Doppler spectrum in the main stems of the pulmonary arteries. Increased PI is the best parameter to detect flow abnormality in this condition. Since the Doppler spectrum depends on cardiac anatomy and function, PI in lung hypoplasia seems to be reliable only when cardiac defects are absent.

Embryonic middle ear mesenchyme disappears by redistribution

OBJECTIVE

The fate of embryonic middle ear mesenchyme from a postgestational infant ear has been speculative. Recently a volume analysis of human neonatal temporal bones demonstrated that embryonic mesenchyme disappeared by redistribution and thinning to surface a growing middle ear space. If this model is accurate, interaction with amniotic fluid and the gestational environment should not influence mesenchymal behavior. Therefore an opossum marsupial model was compared with human data.

METHODS

The temporal bones of opossum pups (20 to 36 days of age) were sectioned for histologic analysis. Computations were made for the volume of the middle ear air cavity (VAC), volume of the bone cavity (VBC), volume of mesenchyme (VM), and percentage of the middle ear occupied by mesenchyme (%M), which were plotted against height using regression statistics. These data were compared with human neonatal (0 to 30 days of age) temporal bones.

RESULTS

In both the opossum and the human the VAC and the VBC increased in parallel with growth of the body. In the opossum the VAC and VBC both grew at 0.148 mm3/mm of body length. In humans, both the VAC and VBC grew 6.1 mm3/cm of body length. The VM in the opossum remained constant at 0.98 mm3, regardless of body length. In humans the VM remained constant at 71.7 mm3, regardless of body length. Therefore the %M proportionately decreased inversely with increasing ear size in both the opossum and the human neonate.

CONCLUSION

This study supports a simple and credible explanation for the illusion of mesenchymal disappearance in the neonatal middle ear. The mesenchymal connective tissue redistributes to cover a larger surface area in a persistently enlarging cavity. These findings occur in different species, whether gestation is completed in an intrauterine or an extrauterine environment.

Follow-up of children after fetal treatment for obstructive uropathy

BACKGROUND

Improvement in the ability to evaluate fetuses with obstructive uropathy, combined with technologic advances, has allowed successful fetal treatment of these conditions in Japan. We analyzed the prenatal and postnatal clinical courses of patients who underwent shunt placement in utero.

METHODS

We treated 6 patients who underwent fetal intervention and were transferred to us for urologic management. Gestational age at detection of abnormalities ranged from 11 weeks to 31 weeks, and fetal intervention was done between 16 weeks and 32 weeks. Excluding 1 infant who was delivered 6 days after the intervention, the mean period between shunt placement and delivery was 17 weeks.

RESULTS

Urologic pathology included prune belly syndrome with urethral hypoplasia in 3 patients, cloacal anomaly in 1, posterior urethral valves in 1, and pelviureteric junction stenosis of a solitary kidney in 1. Four patients required ventilation support in the neonatal period, and 2 of them suffered frequent infections during follow-up. Five patients who underwent vesico-amniotic shunt placement continue to require clean intermittent catheterizations via vesicostomy because of hypoactive detrusors and hypoplastic urethras. After urologic treatment, serum creatinine in 5 patients reached a minimum of less than 0.4 mg/dL at some time during the first year of life. Another patient with a minimum creatinine level of 1.0 mg/dL has moderate renal insufficiency.

CONCLUSION

From our series, it appears that early (before 20 weeks of gestation) shunt placement in severe lower urinary tract obstruction may benefit renal and pulmonary function. However, its efficacy in regard to bladder function remains questionable: shunt placement does not permit regular storage and evacuation, which may be essential for functional bladder development.

Cloacal dysgenesis sequence: observations in four patients including three fetuses of second trimester gestation

Cloacal dysgenesis is a rare malformation sequence. We studied cloacal dysgenesis in four fetuses, including three at 18-22 weeks of gestation. All four fetuses showed a smooth perineum with absence of anal, urethral, and/or vaginal openings. The urinary bladder was dilated in 3 cases. The labia majora and minora were absent in the two female fetuses; the scrotum and penis were absent in one male fetus and hypoplastic in the second. The kidneys were either absent (1 case), dysplastic (1 case), or hydronephrotic (1 case). Normal kidneys were seen in a fetus of 20-22 weeks gestation in whom the urinary obstruction was alleviated by a vesicocolonic fistula. This fetus did not have pulmonary hypoplasia. Severe renal anomaly and pulmonary hypoplasia are the limiting factors for the survival of infants born with cloacal dysgenesis. The unique observation of normal kidneys and lungs in one of our fetuses, despite anhydramnios, suggests that the effect of oligohydramnios on lung development may be limited early in gestation, at least up to 20-22 weeks. It may also indirectly support the theory that there are factors other than oligohydramnios that interfere with early lung development, such as reduced production of a pulmonary growth factor by the kidney or reduced proline production by malformed kidneys, that may cause decreased collagen formation and result in hypoplastic lung mesenchyme.

Normal pulmonary function in a monoamniotic twin discordant for bilateral renal agenesis: report and review

Renal agenesis and obstructive urinary tract anomalies causing oligohydramnios usually result in pulmonary hypoplasia. We report on the first female monoamniotic twin born with a combination of bilateral renal agenesis, agenesis of the urinary collecting system, absent external genitalia, anal atresia and single umbilical artery, compatible with VATER association but with normal pulmonary function. The infant had none of the manifestations of Potter sequence, in particular the facial changes and pulmonary hypoplasia typically associated with bilateral renal a/dysgenesis. The monoamniotic cotwin had normal renal function, such that sufficient amniotic fluid volume was maintained. This patient emphasizes the importance of adequate amniotic fluid volume for normal pulmonary development. The possible underestimation of genital malformations in the VATER association should be considered. Also noteworthy is the rare absence of external genitalia.

Influence of maternal nicotine exposure on neonatal rat lung structure: protective effect of ascorbic acid

The aims of this study were (1) to determine and quantify the adverse effects of maternal nicotine exposure during pregnancy and lactation on neonatal rat lung development, and (2) to establish whether ascorbic acid will protect the neonatal rat lung against the adverse effects of maternal nicotine exposure. Pregnant rats received nicotine (1 mg/kg body mass/day) subcutaneously during gestation and lactation. A second group received nicotine and ascorbic acid (1 mg/kg body mass/day). The control animals received saline subcutaneously. The results illustrate that maternal nicotine exposure results in (a) a decreased (P < 0.001) radial alveolar count (RAC), (b) an increase (P < 0.001) in destructive index (DI), (c) an increased (P < 0.001) linear intercept (Lm), (d) an increased (P < 0.001) abnormal alveolar attachment index (AAA) (e) and an increase in septal cellularity. Ascorbic acid does not protect fetal lung development against the adverse effects of maternal nicotine exposure. However, after birth ascorbic acid prevents further deterioration of the DI, AAA and Lm, whereas the RAC and thus the number of alveoli was even higher than in control neonatal rat lung. No further increase in cellularity occurred. The reason for this response to ascorbic acid supplementation is under investigation.

Neonatal mesenchyme temporal bone study: typical receding pattern versus increase in Potter's sequence

The fate of mesenchyme, which lines the fetal and newborn bony middle ear, is not well understood. The authors wished to test previous observations that a greater amount of mesenchyme was found in Potter's sequence (renal anomalies, pulmonary hypoplasia, and oligohydramnios). Using celloidin-embedded neonatal temporal bones (68 cases, 123 ears), with clinical and autopsy information, middle ear volumes were compared among diagnostic groups using analysis of variance. In 16 ears of Potter's sequence cases the volume of mesenchyme increased in proportion to the size of the middle ear. Conversely, in all other cases the volume of mesenchyme remained constant compared to increasing middle ear size. Both the volume of the bony middle ear and the volume of the air cavity increased at 15 mm3/500 g of body weight (gbw). Mesenchyme percentage decreased by 2%/500 gbw. Middle ear mesenchyme appears to recede rather than reabsorb. However, in Potter's sequence cases the volume of mesenchyme increases, raising issues of a missing renal signal that inhibits mesenchymal growth under normal circumstances.