We present the case of a baby boy, with antenatal finding of bilateral enlarged echogenic lungs, who developed severe postnatal respiratory failure. Two important differential diagnoses, which have an impact on antenatal and postnatal management, are discussed. Fetal ultrasound, MRI and postmortem MRI images are presented and findings correlated with the autopsy findings.
- neonatal intensive care
- congenital disorders
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Congenital pulmonary airway malformations (CPAMs) are rare with an incidence of 1 in 30 000 live births. These lesions are usually unilateral and unilobar. Our case describes an even rarer diagnosis of bilateral CPAM in an extremely preterm neonate who developed severe respiratory failure after birth. The antenatal presentation of the baby described was atypical of CPAM (which usually present as distinct lung lesions) and had overlapping features with congenital high airway obstruction syndrome (CHAOS). Differentiating these two conditions is important for potential fetal therapy and postnatal airway management. The subsequent discussion focuses on the distinguishing prenatal imaging features of CHAOS and bilateral extensive CPAM and correlates antenatal and postmortem imaging with autopsy findings. We also present the utility of postmortem MRI in places with limited access to autopsy.
A male infant, first child of non-consanguineous parents, was born at 26+1 weeks’ gestation via a vaginal delivery. The mother had no other significant medical issues apart from gestational diabetes requiring insulin. In the antenatal routine morphology scan at 20 weeks’ gestation, the fetus was found to have bilateral enlarged, echogenic lungs. The rest of the fetal anatomy appeared normal. After tertiary ultrasound review confirming bilateral, asymmetrically enlarged lungs (right larger than left) with flattening of the hemidiaphragms and cardiac compression, a differential diagnosis of CHAOS or bilateral CPAM was proposed as the most likely causes for these appearances (figure 1). A fetal MRI performed at 24 weeks’ gestation demonstrated interval development of polyhydramnios and bilaterally enlarged lungs with flattening but not eversion of the diaphragms (figure 2). Of note, the upper trachea was patent and of normal calibre but could not be seen lower in the chest; however, image quality was affected by motion degradation, maternal increased body mass index and polyhydramnios which may have impaired lower tracheal visualisation. Differential diagnoses proposed were, in order of likelihood, bilateral CPAM, distal tracheal agenesis with tracheo-oesophageal fistula and nutmeg lung due to primary pulmonary lymphangiectasia. After counselling with fetal medicine specialists, the parents declined amniocentesis. Cell-free DNA testing had been low risk for the common trisomies.
The mother presented with threatened preterm labour at 25+6 weeks’ gestation, likely related to progressive polyhydramnios (amniotic fluid volume was 27 cm at 24+1 weeks’ gestation, the last formal assessment), and a course of antenatal steroids was completed. The infant, weighing 830 g, was delivered vaginally, 2 days later, after labour ensued. He was apnoeic and bradycardic and was intubated shortly after birth. Intratracheal placement of endotracheal tube was confirmed with a CO2 detector and surfactant was administered in the delivery suite. An enteric tube passed easily. The first arterial blood gas showed a pH 6.92 pCO2 73.8 PaO2 52 BE- 17 lactate 9.5 in FiO2 100%. Figure 3 shows the first chest X-ray after birth.
Outcome and follow-up
Oxygenation continued to worsen with widening preductul and postductal SpO2 difference despite escalation to high-frequency oscillatory ventilation, inhaled nitric oxide and inotropes. Ventilation transiently improved with the lowest pCO2 of 47 mm Hg at 2.5 hours of life. Unfortunately, this was not sustained and the infant progressed into respiratory failure and intractable respiratory and metabolic acidosis. Care was redirected towards palliation in consultation with the family and the infant died 21 hours after birth.
A postmortem MRI (figure 4) was performed 10 hours after the baby’s death. Both lungs were grossly abnormal in signal and texture. Multiple cystic spaces were seen throughout the lungs and the right lung was grossly hyperinflated and had herniated across the midline producing mediastinal shift. The upper lobe of the left lung and right lower lobe appeared to be relatively less affected by these changes. The entire trachea was seen to be present, patent and normal in caliber. These findings were consistent with the diagnosis of bilateral CPAM.
Autopsy showed the larynx, trachea and main bronchi were patent and normal. The right lung (figure 5A–C) was massive with four lobes (60×55×40 mm; 67 g) and pushed the heart and mediastinum to the left. On slicing, the entire right lung was replaced by solid pale tan parenchymal mass with scattered slit-like or cystic structures, less than 2 mm in diameter. The left lung (40×30×22 mm; 14.1 g) had two lobes and was predominantly replaced by solid parenchymal mass showing features similar to the right lung. There was minimal residual normal lung parenchyma at the left upper lobe. Microscopic sections from both lungs showed irregular, stellate-shaped, bronchiole-like structures and ductules lined by uniform cuboidal to columnar epithelial cells giving an ‘adenomatoid’ appearance. No mucous cells, cartilage, rhabdomyomatous or blastemal cells were present (figure 5D). The solid areas were devoid of bronchi and there was paucity of vessels. Appearances were consistent with CPAM type III. Extensive involvement with little normal tissue explained the subsequent severe postnatal course.
Bilateral CPAMs are rare and have a varied presentation. Walker et al1 reported 2% of prenatally diagnosed congenital lung anomalies were bilateral CPAMs. The neonatal presentation of bilateral CPAMs is varied and mostly benign. They are detected antenatally as discrete lesions. Childhood and adult presentations have also been described.2 3
In a series described by Maas et al,4 one of the cases describes a fetus with bilateral lung masses at 20 weeks’ gestation. The baby was eventually born at 27 weeks’ gestation and died soon after birth with severe respiratory distress. There were some similar antenatal features to the case we describe including the presence of mediastinal shift and flattening of the diaphragms, however it differed from our case in that the masses in both lungs were discrete and hydrops of the fetus was an early feature.
The case described here presented a diagnostic dilemma, with prenatal US findings atypical for both CPAM and CHAOS. The classic fetal ultrasound and MRI findings of CHAOS include: (1) bilateral enlarged echogenic lungs, (2) flattening or inversion of the diaphragms, (3) centrally positioned and compressed heart, (4) dilated tracheobronchial tree (classically below the vocal cords where obstruction is typically located) and (5) ascites and placentomegaly. While the first two features were present in this case, the latter three were not. In addition, fetal MRI showed the upper trachea was patent and not dilated although the main bronchi could not be visualised due to image quality. We reasoned that the lower airways may not be dilated and the diaphragms not inverted if CHAOS were accompanied by a tracheo-oesophageal fistula.
Other features in the antenatal imaging favoured bilateral CPAMs. Of note, the fetal lungs were asymmetrically enlarged (see figures 2 and 3 postmortem MRI); the right more affected than the left, with mediastinal shift to the left. In CHAOS, the lungs are symmetrically enlarged with the heart compressed in the centre of the chest. Postnatal findings (easy intubation, normal pCO2 at 2.5 hours) excluded significant laryngeal or tracheobronchial obstruction.
Differentiating the pathology in a fetus with bilateral echogenic lungs is of critical importance as the antenatal and postnatal counselling and management are different. While prognosis for CHAOS is generally poor, the mortality for bilateral CPAMs can be variable and depends on the amount of residual normal lung tissue. Therefore, establishing the diagnosis and prognosis with antenatal imaging changes parental counselling. In newborns with suspected CHAOS, prebirth planning should include consideration of an ex-utero intrapartum treatment procedure and presence of ear, nose and throat surgeons at delivery to assist with establishing an airway. In addition, fetal bronchoscopy has been described as a possible treatment modality for fetuses with airway obstruction (especially those with unilateral involvement), although this has not been performed in our centre to date.5 6 In our case, the prenatal MRI allowed the managing clinical team and parents to be prepared for successful intubation but likely immediate or increasing problems with maintaining oxygenation due to the extent of parenchymal lung abnormality. Identification of polyhydramnios was relevant both as a marker of the severity of the lung disease and a predictor of preterm labour and delivery.
One of the unique features in our case is the availability of both the postmortem MRI and autopsy. While microscopic diagnosis is the gold standard, it may not be widely available, and international data7–9 indicate parents more often refuse than accept conventional autopsy even when the latter is available and offered. In our case the postmortem MRI correlated well with the autopsy findings. This highlights the utility of postmortem MRI where an autopsy is unavailable or refused. Minimally invasive and non-invasive autopsy (including postmortem MRI) has much better acceptability than conventional autopsy among parents.10
Parent’s perspective: Before birth, we thought the uncertainty of diagnosis, prognosis and pregnancy length was the biggest cause of stress. Our inability to have certainty in these areas was overwhelming, as we were left to process all possible outcomes and their associated emotions.
After birth of our baby, we were hopeful that somehow he would be able to pull through and that we could keep him alive, so long as he was not in any pain, long enough to make some headway with his lungs. We were not sure what was happening with his lungs or if there was any chance of full recovery.
After his death, we wanted to help others learn from our experience and have the details of his findings used to assist in other cases with similar variables—with the hope of providing some certainty to mothers and fathers who face a similar diagnosis.
Then and now, we are thankful to all doctors and nurses for their enormous efforts and the diligent care provided during pregnancy and after the birth of our little one.
Differential diagnoses of antenatally detected bilateral enlargement of the lungs must include congenital high airway obstruction syndrome (CHAOS) and bilateral congenital pulmonary airway malformation (CPAM).
Prenatal MRI is an important tool in differentiating bilateral CPAM from CHAOS by facilitating tracheal evaluation.
Postmortem MRI can be a useful alternative to conventional autopsy when this is either not available or refused.
Contributors All authors have contributed to this report, were involved in the patient’s care and approved the final version of manuscript. PC: compilation of case data and first draft of the manuscript. SG: fetal MRI and postmortem MRI. AR: fetal ultrasound. AMo: anatomical pathology. AMa: neonatology, parental consent and reflection.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.