Rare cause of infantile respiratory distress: A case report of lobar overinflation in a Kenyan neonate

INTRODUCTION

Congenital lobar overinflation (CLO) is a rare non-vascular lung disease that presents as respiratory distress in the neonatal period with associated imaging findings of lobar overinflation.^[1] In Africa, few case studies have been reported.^[2,3] Clinical symptoms resulting from compression and atelectasis of adjacent lung and mediastinal structures are easily mistaken for pneumonia, a highly prevalent disease in our region.^[1-3]

It has an incidence of 1:20,000–1:30,000 live births and commonly affects the left upper and right middle lobes; it may be bilateral or multi-lobar.^[1-4] It is postulated that CLO may be caused by one of the following abnormalities: a defect in bronchial morphogenesis, endobronchial obstruction by mucus or unfolding tissues, or external compression of lung structures by mediastinal masses in the prenatal period.^[1,3,4]

Improved and more accessible fetal imaging has increased the diagnosed cases of CLO, but it may still be missed during the routine fetal ultrasound.^[1,3] It appears as a bright echogenic fluid-filled mass or cystic lesion with mediastinal shift and contralateral lung compression.^[5] In Kenya, mothers often do not have a fetal ultrasound done at the antenatal care clinic (the ultrasound prevalence rate is 22% and the clinic attendance is 66%).^[6,7]

Other imaging modalities such as chest radiographs, computerized tomography (CT) scan, and angiography may be helpful in diagnosing pneumothoraces, microcysts, vascular lesions, and differentiating other cystic lung malformations postnatally.^[1,4] In specialized centers, prenatal ultrafast magnetic resonance imaging (MRI) is preferable as it avoids radiation.^[5]

CASE REPORT

A 21-day-old full-term male neonate was admitted with an acute onset of fever and respiratory symptoms. His mother reported that she had an uneventful pregnancy, but no antenatal ultrasonography was performed. He had fast breathing since birth and was admitted to the newborn unit (NBU) for 9 days at his primary health facility. Our patient was on oxygen therapy by nasal prongs for most of that stay and received a 7-day course of crystalline penicillin and gentamicin for pneumonia, before his discharge home (off oxygen). He was exclusively breastfed but was reported to have poor weight gain by his mother, and this was confirmed at the post-discharge review clinic. No respiratory distress was reported when he was discharged home and during this follow-up period.

On admission to our facility, he was irritable, afebrile, pink, and not cyanosed. He had features of respiratory distress, reduced right-sided breath sounds, and bilateral basal crepitations. He also had tachycardia, a displaced cardiac apex beat (6^th intercostal space lateral to the mid-clavicular line), normal heart sounds, and a displaced liver (2 cm below the right costal margin). The other systems were essentially normal. No mention of lobar over-inflation in the previous chest radiograph was noted in his discharge medical report.

He was started on oxygen by nasal prongs, intravenous maintenance fluids, and tests were performed that included imaging to check for infection and possible cardiac pathology. No antibiotics were initiated as he was afebrile and the infection biomarkers, C-reactive protein and pro-calcitonin, were low. A chest radiograph confirmed right lobar over-inflation and an echocardiogram confirmed apical shift, but no other cardiac pathology was noted. Sputum multiplex polymerase chain reaction test detected adenovirus [Figure 1].

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Figure 1:

A 3 week old male neonate with right lobar over-inflation. Chest radiograph shows retro-sternal lobar herniation, mediastinal shift (arrow) and right lobar over-inflation (asterisk).

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His respiratory distress progressed, and continuous positive airway pressure (CPAP) non-invasive ventilation was commenced. He did well after 2 days and was eventually weaned off CPAP and oxygen therapy. A CT scan of the chest confirmed a right middle lobar over-inflation and bilateral pneumonic features. After an assessment by the cardiothoracic surgeon, he was discharged home to recover from the current pneumonia and was to be followed up in 2 weeks at the chest clinic, where a lobectomy would be planned. Unfortunately, he succumbed at their nearby primary health facility a few days before the planned surgery. His demise was thought to be from a new episode of pneumonia and sepsis [Figures 2a and b].

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Figure 2:

A 3 week old male neonate with right lobar over-inflation. (a) Axial computed tomography (CT) lung view shows right middle lobe over-inflation and retro-sternal herniation (asterisk), while the arrow indicates contra-lateral lung compression and pneumonic process. (b) Coronal CT lung view also shows right middle lobe over-inflation (asterisk). Note the contra-lateral lung compression and mediastinal shift to the left.

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DISCUSSION

Our case presented with early symptoms that were likely caused by airway and lung compression associated with recurrent respiratory tract infections. He eventually succumbed before surgery could be performed. He had an initial chest radiograph, but the diagnosis of CLO was missed, as the focus was on managing a respiratory infection at the primary facility. A lack of awareness of CLO likely contributed to the chest radiograph features of CLO being missed.

Surgery is indicated for symptomatic lesions; this relieves compression, thus preventing further episodes of infection or bleeding, and it also confirms the diagnosis by providing a specimen for a histologic examination.^[1,5,6] However, if surgery is performed while an infective process is ongoing, like in our patient, the operative mortality and morbidity are greater.^[1,4,8] In such a situation, the clinical team finds itself in a dilemma: a higher chance of death due to operating while there is an ongoing infection versus an increased chance of death from recurrent pneumonia. We weighed the risk and preferred to wait and operate after resolution of the pneumonia.

Other cystic thoracic malformations that should be considered in neonates include: bronchopulmonary sequestration, congenital pulmonary airway malformation (CPAM), and bronchogenic cysts. Sequestrations are vascular lesions within the lobe with no airway communication and are usually situated in the left lower lobe. A unilateral and unilobar lesion that is multi-cystic on a CT scan may be a CPAM. CPAMs are caused by a disruption of the fetal airway morphogenesis and may resemble CLO on imaging but differ histologically. CPAMs consist of proliferations of the terminal respiratory structures: these form cysts with polypoid projections of the mucosa, an increase in smooth muscle and elastic tissue within the cyst walls, an absence of cartilage, and the presence of mucus-secreting cells with no evidence of inflammation.^[4,8]

Bronchogenic cysts are foregut mesenchyme derivatives often found in the middle mediastinum as a solitary, homogeneous, large fluid-filled, well-defined ovoid or round cyst near the carina. They contain cartilage, mucinous glands, and smooth muscle lined with respiratory epithelium. Large cysts may present similarly to CLO with lobar overinflation and compression of adjacent structures.^[4,8]

The histology of CLO is generally normal, with mild alveolar dilation, without malformation or destruction of alveolar septa. In some cases, an increase in the number of alveoli occurs, causing a polyalveolar hyperplastic lobe.^[1,4,8]

Cystic lung lesions may regress during the antenatal period, with normal lung imaging noted during the postnatal follow-up. They may remain asymptomatic until the lesion enlarges due to inflammation or as the infant grows.^[1,5,8]

Surgical options include video-assisted thoracoscopic surgery (VATS) or open posterolateral thoracotomy and resection of the affected lobe. VATS is preferable in asymptomatic patients but is associated with conversion to open surgery in symptomatic cases.^[4,9]

Conservative management has been reported in asymptomatic cases, but the risk of missing a malignancy and not confirming the diagnosis by histology, especially for post-natal diagnosed lesions, remains. Diagnosis after 6 months of age, size of the lesion, number of affected lobes, non-regression of the mass, and risk of complications such as compression symptoms, hemoptysis, pneumothorax, recurrent pneumonia, and poor lung development, will influence the decision on resection of the lesion at the time of diagnosis.^[1,4,9,10]

Congenital cystic lung lesions have been associated with pleuropulmonary blastoma (PPB) with an incidence of 4%, which can occur even after surgery. Multifocal or bilateral cysts which complicated by a pneumothorax are likely PPB.^[4,8,10]

CONCLUSION

To improve the outcome of cases with cystic lung malformations in our region, we need to improve screening for these lesions in both the antenatal and postnatal periods. Improved awareness of the ultrasound and chest radiograph features by clinicians will aid in detection. Neonates with respiratory distress from birth should have a chest radiograph done to detect infections and thoracic malformations. Further imaging, such as a CT scan or MRI, and angiography, differentiates CLO from other cystic lung malformations and is used to plan for surgical management. Cases detected in the antenatal period should be followed up postnatally for remission, development of complications, normal lung development, and risk of malignancy. Surgery should be performed for symptomatic neonates to relieve symptoms and confirm a histologic diagnosis of the lesion. Asymptomatic cases can be managed conservatively, but the risk of complications remains.