Congenital bronchopulmonary foregut malformation: systematic review of the literature

Communicating bronchopulmonary foregut malformation (CBPFM) is a rare congenital anomaly defined by a patent congenital communication between the esophagus or stomach and an isolated portion of the respiratory tract. Lesions including a lobar bronchus arising from the esophagus are described as an esophageal bronchus. If the main bronchus originates from the esophagus, it is termed esophageal lung [1]. In 1992, based upon the occurrence of related defects and the level of the communication, Srikanth et al. reviewed 57 cases and proposed a system to classify CBPFM into four groups [2]. Group I is associated with esophageal atresia and tracheoesophageal fistula and contains 2 subdivisions, that is, group IA, total sequestered lung communicating with the foregut, and group IB, Sequestered anatomic lobe or segment communicating with the foregut. Group II is characterized by the absence of a mainstem bronchus arising from the trachea and the total sequestered lung (usually the right) communicating with the lower esophagus. Group III occurs when an isolated part of the lung is communicating with the esophagus and group IV occurs when there is communication between a normal bronchial system and the esophagus.

Early diagnosis of CBPFM is difficult for the rarity of this entity and the nonspecific symptoms. We presented an infant with CBPFM and strictly reviewed the available literatures since Srikanth’s classification proposed to describe the demography, clinical presentation, pathology, imaging features, treatment and prognosis of CBPFM.

One hundred and seventy-two papers were identified by searching the databases, one additional article was identified by manual searching. No reports were repetitive. Eighty-three reports were eligible for full-text screening. Of them, 38 papers matched our criteria and were included [2, 4‐40]. The selection study process is showed in the PRISMA flowchart in Fig. 2. They included 60 cases of CBPFM. The 134 papers excluded were review articles, animal cases, published in a language other than English or malformation not meeting the diagnostic criteria depicted by Srikanth et al. Therefore, 61 cases were reviewed including our case (Table 1). The table in the Additional file 1: Table S1 shows the details of the included cases.

The term congenital bronchopulmonary foregut malformation was proposed by Gerle et al. in 1968 to describe either an intralobar or an extralobar sequestration communicating with the gastrointestinal tract [41]. Srikanth et al. proposed the classification based on reviewing 57 cases of CBPFM [2].

The embryogenesis of CBPFMs is not clear though it was treated as a sub-type of bronchopulmonary foregut malformation including foregut vascular abnormalities, lung parenchymal abnormalities and airway anomalies [42]. This malformation was proposed to occur when there was a congenital communication between the lung and foregut because of a focal mesodermal defect. The aberrant lung tissue was separated with the rest of the lung and trachea during the rapid elongation of the esophagus, which accounted for the missing portion of the corresponding bronchial tree [27]. CBPFM also occurred in an adriamycin-induced rat model of esophageal atresia. The observations were consistent with the hypothesis that CBPFM and EA were variations of the same spectrum of abnormalities and may have a similar etiology [43].

Our series were in agreement with that reported by Srikanth et al. in the female and right-side preponderance. The distribution of numbers among groups was similar. But the mortality in Srikanth’s series was 24.6% compared with 17.4% after 1992. The increased survival rate may be attributed to improvements in critical care management of affected newborns. Nevertheless, delay of diagnosis was still common for the rarity of the entity. Especially for group I, the existence of CBPFM is obscured by the presentation of EA/TEF. Though the abnormal pulmonary tissue could be aerated through the communication of the esophagus before the inflammation commenced, collapse of the ipsilateral lung was the typical presentation. Hence the persistent or worsening unilateral lung collapse with or without EA/TEF should raise the suspicion and warrant further examinations to exclude CBPFM. UGI was the first choice to delineate the bronchial tree connected to the esophagus, but the value was limited in group I due to atresia of the proximal esophagus. In this circumstance, bronchoscopy should be considered. Computed tomography (CT) is helpful in evaluating the pulmonary damage and vascularization.

Prenatal diagnosis was possible in some high-volume institutions by experienced radiologist [20]. In fetal MRI, a tubular T2 hyperintense structure (bronchocele) directed from the lung lesion to the gastroesophageal junction can be seen. The congenital lung lesions are now more commonly recognized on screening anatomic ultrasound, and CBPFM should be considered as a differential diagnosis.

No predisposing factors have been identified in the etiology of CBPFM, although the observed concordance of this lesion in a pair of twins argues in favor of a possible underlying genetic predisposition. Because the frequency of the associated malformations is high, preoperative screening examinations was important. Echocardiography is mandatory preoperatively as cardiovascular malformations were found in 18.0% of the cohort of patients. VACTERL association was not uncommon and a comprehensive examination should be performed. Accompanying airway stenosis was the most difficult problem which always resulted in long-term morbidity. The management requires extensive experience.

Surgery was the only method to effectively manage this malformation. Conventional treatment is resection of the hypoplastic lung which has been destroyed by recurrent infection. Pneumonectomy was performed in most patients with group IA or group II. Unilateral lung resection in neonates and infants was well tolerated. However, the prevalence of long-term consequences, such as chest wall deformation, scoliosis and postpneumonectomy syndrome were unclear. One patient developed postpneumonectomy syndrome in our review. A tissue expander was inserted, and the symptoms subsided with growth. The other choice was reconstruction of the esophageal bronchus. This was the theoretically preferential procedure to preserve the affected lung and prevent the complications of pneumonectomy. The first successful reconstruction effort was reported by Michael et al. in 1997 [16]. Seven reconstruction procedures were included in our study with one simultaneously undergoing pulmonary artery reimplantation. The results were dismal due to the airway stenosis or accompanying malformations. Four out of the 5 surviving cases presented with varying degrees of airway stenosis which required surgical corrections or dilatations. The results of reported reconstruction surgery were unsatisfactory. Therefore, attempts to reconstruct the bronchus should be confined to stable patients with non-infectious lung after exclusion of significant associated malformations.

There are some limitations in our study. Firstly, selection bias cannot be ignored due to the possibility that more successful interventions were published. Nevertheless, our study samples may be representative because the distribution of sex, classifications and affected side were similar to previously reported studies. Secondly, the outcomes of 15 cases included were not reported, and these cases were excluded from calculated mortality. The lack of adequate cases and information may result in inaccurate mortality rate.

CBFPM is rare and the outcome depends on the associated malformations and early recognition. Persistent opaque hemithorax with ipsilateral mediastinal shift on chest radiograph should raise the suspicion of CBFPM in infants. UGI is the preferred method to delineate the abnormal bronchus communicating with the esophagus. CT and bronchoscopy are also valuable in diagnosis or screening for accompanying malformations. Echocardiography is mandatory due to the high frequency of associated congenital heart disease. Resection of abnormal pulmonary tissue, lobe and even unilateral lung is the reasonable treatment in most cases. The decision of parenchymal sparing surgery, such as reimplantation of bronchus, should be taken cautiously due to the high possibility of long-term complications.