Intralobar pulmonary sequestration masquerading as congenital lobar emphysema.

Intrapulmonary sequestrations are quite uncommon in pediatric age group. The preoperative diagnosis of pulmonary sequestration is not possible in most of the cases. A 2-year-old boy presented with recurrent episodes of chest infections and respiratory distress. A preoperative diagnosis of congenital lobar emphysema was made on the basis of chest radiograph and computed tomography scan. At operation, an intralobar pulmonary sequestration was found. The sequestration cyst was excised with uneventful recovery.

INTRODUCTION

Pulmonary sequestration is a very rare anomaly in the pediatric age group, especially intralobar variety. It is comprised of nonfunctioning primitive lung tissue, having no communication with the tracheobronchial tree and contains a systemic arterial supply.[1] The preoperative diagnosis is usually not a pulmonary sequestration in most of the patients. Computed tomogram (CT) scan, magnetic resonance imaging (MRI), and angiography are important tools for its diagnosis; however, the index condition may simulate other lesions of the chest as well.[23] A case of intralobar pulmonary sequestration mimicking as congenital lobar emphysema is being reported. To the best of our knowledge, this type of presentation is not reported before.

CASE REPORT

A 2-year-old boy, already diagnosed as a case of congenital lobar emphysema on chest radiograph and CT scan, was referred to our department for the surgical excision of the emphysematous lobe. The medical history was consistent with multiple admissions to some other hospitals for repeated chest infections. The baby attained first episode of chest infection at the age of 6 months when he was diagnosed as having pneumonia. Since then, the baby had to complete a course of antibiotics every 3 months for repeated chest infections.

At the time of admission to our department, the baby was vitally stable except for mild tachypnea. The chest radiograph and CT scan of the patient delineated hyperinflated lobe in the right hemithorax with bronchovascular markings, consistent with the diagnosis of congenital lobar emphysema [Figures 1 and 2]. The laboratory parameters were within normal limits.

Figure 1

Chest radiograph showing hyperinflated lung with bronchovascular markings in the right hemithorax

Figure 2

CT scan of the same patient with fine delineation of the radiographic findings

The patient was prepared for right thoracotomy. At surgery, a hyperinflated emphysematous lung tissue was found within the visceral pleural investment. This lung tissue had no communication with the normal tracheobronchial tree; instead it was adherent with upper and middle lobes. The emphysematous lung tissue was dissected from the lobes. The arterial supply was coming from the lung tissue (bronchial artery) whereas venous supply was ending up into the hilum [Figures 3–5]. After excision of the emphysematous lung tissue some minor air leak was observed from the upper and middle lobes from where the emphysematous tissue had been excised. Our operative diagnosis was intralobar pulmonary sequestration.

Figure 3

The only attachment of emphysematous tissue with others was blood vessels

Figure 5

The excised emphysematous intralobar sequestration

All three lobes are present inside the chest cavity after excision of the emphysematous lung tissue

Histopathology of the excised specimen confirmed the primitive lung tissue with emphysematous changes. The minor air leak was managed with the chest tube that ceased to occur on the second postoperative day. The chest tube was removed on 5th postoperative day. The patient was asymptomatic at 6 months follow-up.

DISCUSSION

There are two types of pulmonary sequestrations, identified on the basis of its anatomical location, intralobar pulmonary sequestration, and extralobar pulmonary sequestration. Intralobar sequestrations are surrounded by normal lung parenchyma without a separate pleura as in the index case, whereas, extrapulmonary sequestration is enclosed completely in its own pleural sac.[12] Intralobar pulmonary sequestration is four times commoner than the extralobar variety. Both the varieties differ in location, venous drainage and age of presentation. The venous drainage of intralobar variety is pulmonic whereas that of extralobar variety is systemic. Intralobar pulmonary sequestration presents in adulthood, on the other hand, most of the cases of extralobar pulmonary sequestration present in the initial few years of life.[1-4]

The preoperative diagnosis is usually not possible in every case. In suspected cases, CT scan of the chest with contrast and angiography are important diagnostic modalities for the delineation of the sequestration as well as its blood supply.[5] The presenting symptoms usually are repeated chest infections, and vomiting in some cases. The diagnosis is usually made peroperatively in most of the cases.[56] In our case, the presentation of the patient was with recurrent chest infections for which he had been investigated in the pediatric medical department. Radiological investigations depicted the lesion as congenital lobar emphysema and similarly on the basis of history and investigations our preoperative diagnosis was also congenital lobar emphysema. At operation, the diagnosis of intralobar pulmonary sequestration was made on the basis of lack of communication of the emphysematous lung tissue with the normal tracheobronchial tree, aberrant blood supply, and the presence of all the three lobes in the right hemithorax after excision of the emphysematous lung tissue. Moreover, histopathology confirmed the presence of primitive lung tissue with emphysematous changes in the excised specimen. The other differential diagnosis should be congenital segmental emphysema but if it would be so, then there should be major air leaks in the involved lobes and it did not happen in our case.[7]

The emphysema in the sequestration in the absence of any overt communication with the tracheobronchial tree can be explained by the pores of Kohn. These are minute intraalveolar communications meant for collateral ventilation.[7] It could be assumed that air continued to enter into the sequestration cyst over a long time and when it gained a considerable volume sufficient to compress the normal lobes then it presents with respiratory distress. This event was further aggravated by the respiratory tract infection.

To conclude, intralobar pulmonary sequestration is very uncommon in the pediatric age group. Sometimes it may simulate some other lesions of the chest. Intralobar sequestration can be considered in differential diagnosis of congenital lobar emphysema, though a very rare event in the pediatric age group and not reported before.