Unmasking of left upper lobe bronchial atresia in a case of H1N1 pneumonia

Abstract

We describe a case of H1N1 pneumonia with left upper lobe bronchial atresia. Although bronchial atresia as an isolated occurrence is an innocuous finding, but when it is superimposed by another major insult, it can amplify the disease effect and can have adverse implications leading to significant morbidity. This report highlights the fact that anatomical anomalies can be the cause of inordinately severe or prolonged course of acute respiratory infection in children.

Background

Congenital bronchial atresia (CBA) is a rare developmental anomaly resulting from focal interruption of a lobar, segmental or subsegmental bronchus associated with peripheral mucus impaction (bronchocele, mucocele) and hyperinflation of the obstructed lung segment. Bronchial atresia is often discovered incidentally and is seldom symptomatic. We describe the case of an 8-year-old girl admitted with H1N1 pneumonia with focal hyperlucency in left upper lobe. Further evaluation led to the discovery of left upper lobe bronchial atresia complicating her pneumonia.

Case presentation

An 8-year-old female child was brought to our hospital with complaints of fever, coryza, headache and irritability for the past 10 days. Parents reported gradual progressive course and worsening symptoms in the form of chest in drawing and diminishing sensorium. For these complaints, she was being managed at the local hospital but was referred to our centre in view of suboptimal response to ongoing treatment at the prior facility. On being reviewed, her parents denied any history of recurrent chest infections, wheezing, ear discharge, joint involvements or rash. She was a healthy term baby born by vaginal delivery with no adverse perinatal events. Her past history was unremarkable. She was developmentally normal and was immunised as per national immunisation schedule. Her family history was also non-contributory.

On examination, the child was found to be delirious with irrelevant speech. She was haemodynamically stable but had tachypnoea and moderate subcostal and intercostal retractions. Examination of her respiratory system revealed an asymmetrical finding of reduced air entry in left supra-mammary region and bilateral infra-scapular regions had fine crepitations. Rest of her systemic examination was unremarkable. In view of moderate respiratory distress, she was initiated on respiratory support in the form of non-invasive continuous positive airway pressure.

Investigations

Investigations on patients are detailed in Table 1. During the course of her evaluation, we observed a consistent pattern of focal hyperlucency limited to left upper zone in serial chest radiographs (figure 1A) and so CT chest of the patient was done. Non-contrast CT chest revealed hyperlucent left upper lobe with paucity of bronchovascular markings. Non-visualisation of origin of left upper lobe bronchus (figure 1B) with presence of cyst-like structure (figure 2B) along the course of left upper lobe segmental bronchus confirmed the finding of bronchial atresia. Diffuse patchy area of consolidation was seen in bilateral lungs (figure 2A, B), predominantly in right upper and left lower lobe consistent with active alveolitis. Flexible fibre-optic bronchoscopy was done, which confirmed left upper lobe bronchial atresia.

Table 1.

Haematological and biochemical investigations

6 September 2017		11 September 2017
Hb (115–140 g/L)	123	124
TLC (6000–14 000/cumm)	12 300	16 040
N (22%–48%)	66%	78
PLT (1.5–4.0 lakhs)	4.17	5.11
ALT (13–45 U/L) AST (9–80 U/L)	61 43	47 38
Urea (5–18 mg/dL) Creatinine (0.2–1 mg/dL)	21 0.28	24 0.25
Sodium (130– 145 mEq/L) Potassium (4.1–5.3 mEq/L)	139 4.3	134 5.11
Calcium (9–11 mg/dL) Phosphorus (4–6.5 mg/dL) ALP (150–420 U/L)	9.8 4.7 157
Hs CRP (<1 mg/L)	10.8	7.5
Blood culture	Sterile
pH (7.350–7.450)	7.38	7.41
PCO2 (35–45 mm Hg)	42.5	40.7
PO2 (80–100 mm Hg)	72.3	85.2
HCO3 (22–26 mmol/L)	24.6	23.8
Nasopharyngeal swab for H1N1	Positive

ALP, alkaline phosphatase; ALT, alanine transaminase; AST, aspartate transaminase; Hb, haemoglobin; HCO₃, bicarbonate; Hs CRP, high-sensitivity C reactive protein; N, neutrophils; PCO₂, partial pressure of carbon dioxide; PO₂, partial pressure of oxygen; PLT, platelet count; TLC, total  leucocyte count.

Figure 1.

Chest radiograph, anteroposterior view (A) showing hyperlucency (asterisk) in left upper and mid zone with lack of bronchial markings. Multifocal patchy area of consolidation (black arrow) seen in rest of the bilateral lung predominantly in right upper zone. Minimum intensity projection CT, lung window coronal image (B) showing non-visualisation of origin of left upper lobe bronchus (black double arrow) with hyperlucent left upper lobe (asterisk), consistent with bronchial atresia.

Figure 2.

Axial (A) and coronal (B) non-contrast CT images showing hyperlucent left upper lobe (white asterisk) with paucity of bronchovascular markings. Presence of cyst-like structure (white arrow) seen along the course of left upper lobe segmental bronchus. Diffuse patchy area of consolidation (black asterisk) seen in bilateral lungs predominantly in right upper and left lower lobe consistent with alveolitis.

Differential diagnosis

Differentials of bronchial atresia include other causes of unilateral hyperlucency such as bronchial tumour, Swyer James syndrome, allergic bronchopulmonary aspergillosis, cystic fibrosis or inhalation of a foreign body. These were ruled out by detailed history, CT chest and bronchoscopy in our patient.

Treatment

Our index case went on to require 10 days of respiratory support in the form of non-invasive ventilation along with other supportive measures in the form of oseltamivir for H1N1 pneumonia and antibiotics. Gradually respiratory support was weaned off and she was discharged home after resolution of her illness after 18 days of hospital stay.

Outcome and follow-up

We believe bronchial atresia rendered this patient more vulnerable to the effects of viral pneumonia due to diminished physiological capacity for compensation. The child was followed up every monthly for the first year after discharge and she has remained asymptomatic. Case was discussed with paediatric surgeons and conservative management was planned.

Discussion

CBA is a rare anomaly of lung development. Exact aetiology is unknown but it is postulated that it arises as a result of an ischaemic event in later half of pregnancy. During embryogenesis, airway develops systematically, with the lobar bronchi, subsegmental bronchi and distal bronchioles appearing in the 5th, 6th and 16th weeks of fetal development, respectively. It primarily results from a focal interruption of a lobar, segmental or subsegmental bronchus.¹ Paradoxically instead of reduction in lung volume, there is rather focal emphysematous change due to hyperinflation distal to atretic bronchial segment which in turn due to collateral ventilation through pores of Kohn and channels of Lambert and interbronchiolar pores of Martin.^{2 3}

Jederlinic et al reported 4 cases of CBA and reviewed the clinical, radiographical and pathological features in 82 previously reported cases with CBA.⁴ They documented that most patients were young male adults (64%), and most of them were asymptomatic (58%). It tends to affect apico-posterior segmental bronchus of the left upper lobe in majority, followed by segmental bronchi of the right upper, middle and lower lobes. It is usually an incidental finding. Literature on bronchial atresia in children is scarce given the rarity of symptoms in this age group. In contrast, some groups believe that manifestations in paediatric age group are distinctly different from those in adults. Some of the highlighted findings were that most of these cases in infancy and young children tend to be symptomatic and the most common presentation is recurrent pneumonia. There was a striking female preponderance contrary to the previous reports in adult population. Chest X-ray findings demonstrate a spectrum of features ranging from a large cystic lesion to infiltrative pneumonia or emphysema unlike in adults where there is a uniform finding of perihilar solid or cystic mass with hyperinflation.⁵ Similar features were observed in our index case and we concur with the authors regarding the unique features of this entity in paediatric population.

CBA is largely a radiological diagnosis and bronchoscopy has supplementary role. On chest radiograph, CBA may be mistaken for many common causes of mucoid impaction. CT is the most sensitive imaging modality, and the pathognomic features are the presence of mucocoele with hyperaeration of surrounding lung parenchyma.⁶ CBA can be diagnosed even during perinatal period by using ultrasound bronchofibroscopy.⁷

Artificial positive airway pressure could overinflate the lesion, but non-invasive ventilation was needed as child had moderate respiratory distress due to pneumonia. We were monitoring the hyperinflation of the lesion as well as of bilateral lungs on serial chest radiographs and positive end expiratory pressure was kept optimum to avoid overinflation.

Management strategies are a matter of debate with conflicting opinions. Some people advocate surgery for all patients since a definitive diagnosis is possible whereas majority of people advocate conservative approach.⁸ Indications of surgery include recurrent and severe infection symptoms (such as recurrent pneumonia, dyspnoea, cough or haemoptysis) if medical treatment is ineffective and if malignant lesions cannot be excluded. Among surgical options, lobectomy is preferred to segmentectomy as it is technically challenging because of proximity to bronchial and pulmonary vessels in hilar region. Conservative approach seems reasonable since majority are asymptomatic. Some authors believe that if malformation is discovered during childhood, a surgical excision of concerned lobe may allow normal development of remainder of the lung but the evidence to support this strategy is lacking.⁹

Learning points.

• Anatomical aberrations even though rare can result in exacerbation of superimposed respiratory infections.

• Congenital bronchial atresia (CBA) presents differently in children than in young adults.

• Modern day imaging can rule out most of the conditions mimicking this entity.

• Hallmark radiological abnormalities clinch the diagnosis of CBA unless symptomatic general consensus is on a conservative approach.