Multimodality imaging and surgical management of a rare combination: type 2A bridging bronchus, pulmonary artery sling, and atrial septal defect, a case report

Abstract

We report the case of a 15-year-old female presenting with exertional syncope and a history of refractory respiratory symptoms. Comprehensive preoperative multimodality imaging—including echocardiography, multi-detector computed tomography (MDCT) with three-dimensional reconstruction, and bronchoscopy—revealed a rare complex of congenital anomalies: a type 2 A bridging bronchus (BB), a pulmonary artery sling (PAS), and an atrial septal defect (ASD). Crucially, imaging confirmed the absence of significant tracheal stenosis, thereby obviating the need for tracheoplasty. The patient successfully underwent surgical repair via median sternotomy on cardiopulmonary bypass, which included reimplantation of the left pulmonary artery and patch closure of the ASD. Postoperative MDCT confirmed patency of the reconstructed pulmonary artery and the patient’s symptoms resolved. This case underscores the indispensable role of advanced imaging in the diagnosis and surgical planning of complex congenital cardiopulmonary anomalies, particularly for guiding a tailored surgical approach in the setting of rare associations like BB and PAS.

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1186/s12887-026-07605-9.

Introduction

Bridging bronchus is a rare congenital airway anomaly first described by Gonzalez-Crussi et al. in 1976 [1].This condition is characterized by the right upper lobe being supplied by the right main bronchus, while the right middle and lower lobes are usually supplied by an anomalous bronchus originating from the left main bronchus. This branch courses across (bridges) the inferior mediastinum, giving rise to the name "Bridging Bronchus" (BB). Often complicated by diffuse or focal airway stenosis, this potentially fatal anomaly typically manifests with clinical signs of significant airway obstruction, which can include respiratory distress, apnea, wheezing, stridor, and recurrent respiratory infections. The diagnosis of BB is often challenging because its associated signs and symptoms mimic those of more common conditions, such as bacterial or viral bronchiolitis, bronchial asthma, cystic fibrosis, and foreign body aspiration. Moreover, BB is frequently accompanied by congenital cardiovascular anomalies, including left pulmonary artery sling, atrial and ventricular septal defects, tetralogy of Fallot, patent ductus arteriosus, and coarctation of the aorta [2].

Patients with a pulmonary artery sling, a rare congenital vascular anomaly, most commonly exhibit symptoms of wheezing, stridor, air trapping, and atelectasis due to associated airway compression and frequent tracheal stenosis. In this anomaly, the left pulmonary artery (LPA) arises aberrantly from the posterior right pulmonary artery (RPA) and traverses between the trachea and esophagus to the left hilum [3]. A controversy persists regarding the optimal surgical strategy, focusing on whether LPA reimplantation is always necessary and which tracheal reconstruction techniques are most effective [4]. Pulmonary artery sling is best repaired via median sternotomy, cardiopulmonary bypass, and reimplantation of the left pulmonary artery. This approach ensures excellent patency of the LPA in all surgical patients. Furthermore, preoperative imaging with computed tomography, echocardiography, and bronchoscopy is crucial for precise surgical planning. In cases associated with long-segment congenital tracheal stenosis, one of the preferred techniques for repair involves LPA reimplantation combined with slide tracheoplasty [5, 6].

Case presentation

This report describes a 15-year-old girl who experienced an episode of exertional syncope accompanied by dyspnea and chest tightness. Her history was notable for refractory respiratory symptoms, such as cough and recurrent infections, which had been previously managed as a respiratory disease with only transient improvement. Upon admission, pulse oximetry revealed desaturation with readings of 73% in the left upper limb, 66% in the right upper limb, 81% in the left lower limb, and 70% in the right lower limb. A cardiac systolic murmur was audible on precordial examination, raising suspicion for congenital heart disease. Physical examination revealed normal skin and mucous membrane coloration without peripheral or central cyanosis. No significant digital clubbing or cyanosis of the fingertips or toes was observed. Cardiac auscultation demonstrated a grade II–III/VI systolic ejection murmur at the left upper sternal border, with a fixed and widely split second heart sound (S2). The patient was classified as NYHA functional class II based on exertional dyspnea and a single episode of exertional syncope.No diastolic murmur or pericardial rub was appreciated.Subsequent echocardiography identified two defects in the mid-to-inferior portion of the interatrial septum, measuring approximately 10 mm and 11 mm, with one defect extending toward the inferior vena cava (Fig. 1). The echocardiogram also demonstrated an anomalous origin of the left pulmonary artery from the right pulmonary artery (Fig. 1), suggestive of a pulmonary artery sling. Preoperative transthoracic echocardiography revealed a severely dilated right heart (right ventricular basal diameter: 23 mm; right atrial dimensions: 40 mm × 43 mm) with preserved left ventricular systolic function (LVEF(Left Ventricular Ejection Fraction): 69%). Two moderate-sized, secundum-type atrial septal defects, measuring approximately 10 mm and 11 mm, were identified in the mid-to-inferior interatrial septum. One defect extended toward the inferior vena cava, with a rim of 4 mm from the mitral valve annulus. Color Doppler confirmed exclusive left-to-right shunting across the interatrial septum, with no evidence of right-to-left or bidirectional flow. The left pulmonary artery arose aberrantly from the right pulmonary artery and had an internal diameter of 7 mm, with accelerated flow (Vmax: 232 cm/s), corresponding to an estimated peak pressure gradient of 22 mmHg. Trace tricuspid regurgitation was noted. Right ventricular systolic function was preserved on visual assessment. The pulmonary artery was dilated (main pulmonary artery diameter: 22 mm).To confirm the diagnosis and evaluate the airway architecture, computed tomography angiography (CTA) of the thoracoabdominal aorta with three-dimensional reconstruction was performed (Figs. 2 and 3). This comprehensive imaging confirmed the presence of both a pulmonary artery sling and a bridging bronchus. In this rare airway anomaly, the right main bronchus supplies the right upper lobe, whereas the right middle and lower lobes are supplied by a bridging bronchus that originates from the left main bronchus and crosses the mediastinum. Notably, the anomalous left pulmonary artery was observed to course posterior to this bridging bronchus. According to the classification by Wells et al. [7], the patient was diagnosed with a type 2 A SLPA (sling left pulmonary artery) —a congenital anomaly in which the left pulmonary artery arises aberrantly from the right pulmonary artery and courses between the trachea and esophagus toward the left lung. This type is characterized by the presence of a bridging bronchus, and typically involves stenosis of the trachea and left main bronchus. It is also associated with a varying degree of absence of the pars membranacea and abnormal “napkin-ring” cartilage rings in the trachea and left main bronchus. To evaluate for airway stenosis, assess the pars membranacea, and visualize the tracheobronchial cartilage architecture, bronchoscopy was performed (Fig. 4). The examination revealed no significant airway narrowing; however, it did identify a bronchial anomaly, specifically the orifice of the right intermediate bronchus originating from the mid-portion of the left main bronchus.

Fig. 1.

Echocardiography : ASD(Atrial Septal Defect), RPA (Right Pulmonary Artery), SLPA( Sling Left Pulmonary Artery)

Fig. 2.

RPA (Right Pulmonary Artery), SLPA( Sling Left Pulmonary Artery), BB(Bridging Bronchus)

Fig. 3.

Three-dimensionally reconstructed images, RMB(right main bronchus), LMB༈left main bronchus༉, BB(Bridging Bronchus), RPA(Right Pulmonary Artery), MPA(Main Pulmonary Artery), SLPA(Sling Left Pulmonary Artery), RUL(Right Upper Lobe), RML(Right Middle Lobe), RLL(Right Lower Lobe), RMB(Right Main Bronchus), LMB(Left Main Bronchus)

Fig. 4.

Bronchoscopy revealed no evidence of tracheobronchial cartilage rings or significant airway stenosis

Surgical technique

A median sternotomy was performed to access the pericardium and heart. After systemic heparinization, cardiopulmonary bypass (CPB) was established via cannulation of the ascending aorta and superior and inferior venae cavae. A cardioplegia needle was placed at the aortic root. Following the initiation of CPB, systemic cooling was initiated, the ascending aorta was cross-clamped, and cardiac arrest was achieved by administering cardioplegia solution. Topical hypothermia was maintained with ice slush around the heart. Through a combined right atriotomy and pulmonary arteriotomy approach, the left pulmonary artery (LPA) was identified and dissected free at its origin posterior to the right pulmonary artery (RPA). The LPA was transected (Fig. 5), and the resulting defect in the RPA was closed continuously with 5 − 0 monofilament suture. The LPA was further mobilized to ensure adequate length without tension, then passed posterior to the right main bronchus toward the main pulmonary artery (MPA). An approximately 20-mm incision was made on the left aspect of the MPA near its bifurcation, and the LPA was reimplanted using a continuous 6 − 0 monofilament suture. Patency was confirmed by passing size 13 and 16 probes into the LPA and RPA, respectively. An atrial septal defect (ASD) was then repaired using a bovine pericardial patch sutured continuously with 5 − 0 Prolene (Fig. 5). After thorough de-airing, the ASD closure was secured. The heart was reperfused after rewarming and de-airing. The right atriotomy was closed with a continuous 5 − 0 monofilament suture. After weaning from CPB, heparin was reversed with protamine, and all cannulas were removed. The patient was transferred to the cardiac ICU in stable condition. Postoperative CTA with 3D reconstruction confirmed the patency of the reimplanted LPA (Fig. 5). The patient’s symptoms resolved, permitting successful extubation and subsequent discharge. Postoperative echocardiography demonstrated an intact atrial septal patch with no residual shunt. Bilateral pulmonary arteries were patent (RPA: 12 mm, Vmax 93 cm/s; LPA: 10 mm, Vmax 142 cm/s, PG(Pressure Gradient) 8 mmHg). Right heart chamber dimensions had normalized (right ventricular diameter: 18 mm). Left ventricular ejection fraction was 52% with preserved right ventricular function (TAPSE(Tricuspid Annular Plane Systolic Excursion): 16 mm). No pericardial effusion was noted. These findings confirmed successful surgical repair with good hemodynamic outcomes.

Fig. 5.

Surgical repair of the atrial septal defect and reimplantation of the left pulmonary artery

Discussion

Both Bridging Bronchus (BB) and Pulmonary Artery Sling (PAS) are rare congenital anomalies. Previous literature has indicated a strong association between BB and left PAS [8], which appears to be corroborated in the present case. The clinical manifestations of both conditions often overlap, predominantly featuring respiratory symptoms such as respiratory distress, wheezing, stridor, and recurrent respiratory infections. This symptomatic overlap frequently creates diagnostic challenges. In our patient, the concomitant presence of an atrial septal defect (ASD) with cardiovascular manifestations—including exertional palpitations, cyanosis, and a cardiac murmur—prompted further investigation with echocardiography. This examination subsequently revealed the PAS. Consequently, multi-detector computed tomography (MDCT) and bronchoscopy were performed, leading to the identification of the BB. Three-dimensional CT reconstruction provided clear visualization of the anomalous tracheobronchial tree and pulmonary vasculature, offering crucial support for definitive preoperative diagnosis.

The etiology and pathogenesis of Bridging Bronchus (BB) remain poorly understood. Tracheobronchial development begins in early fetal life. At 30–34 days of gestation, five growth points corresponding to the lobar buds are established: three on the right and two on the left. By 36–38 days, all segmental bronchi have appeared, indicating that BB malformation must occur during this period [9].

Gonzalez-Crussi et al. proposed that “exceptional embryological conditions” might lead to an abnormally prolonged anatomical continuity between the right and left lung primordia [1]. Alternatively, Reid et al. suggested that if an opportunity for association between ectopic mesenchyme and the trachea exists, supernumerary bronchi may form [10]. Similarly, Bremer et al. found that tracheal budding occurs in approximately 5% of human embryos. However, what causes the persistence of this phenomenon, and whether such buds ultimately give rise to BB, remains unknown [11].

Notably, the anomalous connection of the embryonic left pulmonary artery with the pulmonary plexus—resulting in a sling left pulmonary artery (SLPA)—also occurs around the fifth gestational week. This temporal coincidence with the critical period of tracheobronchial differentiation may explain the frequent close association between BB and SLPA. However, due to the rarity of this condition and the limitations of our current understanding of pulmonary embryology, no definitive evidence is available to fully elucidate the developmental mechanism of BB or its relationship with the pulmonary vasculature.

According to the classification by Wells et al., the bronchial anomaly in our patient was consistent with a type 2 A SLPA. In this configuration, the right upper lobe (RUL) is supplied by the right main bronchus (RMB), while the right middle lobe (RML) and right lower lobe (RLL) are supplied by an anomalous bronchus originating from the left main bronchus (LMB). This “bridging bronchus” traverses the mediastinum from left to right. The trachea demonstrated a normal number of cartilage rings from the cricoid cartilage to the carina, with a normal bifurcation at the level of the fourth thoracic vertebra (T4). The origin of the bridging bronchus from the LMB was located at the T5-T6 vertebral level. The branching angle of the RMB was normal, but the branching angle at the pseudo-carina (formed by the LMB and the bridging bronchus) was reduced to approximately 131°, accounting for the characteristic inverted “T” appearance seen in these cases. Type 2 A SLPA is typically associated with tracheal and left main bronchial stenosis due to complete cartilage rings resulting from absence of the pars membranacea. This variant is often more challenging to manage and carries a poorer prognosis, as it is related to intrinsic tracheal stenosis rather than simple external compression by the SLPA [7]. In the present case, preoperative bronchoscopy and CT angiography demonstrated a normal pars membranacea, complete cartilage rings, and no significant luminal narrowing of the trachea or left main bronchus (The left main bronchus was unobstructed (approximate Inner diameter: 7 mm)). Consequently, we elected to proceed with isolated LPA reimplantation without tracheal intervention. This individualized approach is supported by recent evidence suggesting that in patients without significant tracheal stenosis, isolated vascular repair may achieve favorable outcomes.

The present case underscores that Type 2 A SLPA may represent a spectrum of disease rather than a single uniform entity. While the literature emphasizes the frequent coexistence of intrinsic tracheal stenosis in this subtype [7], our findings demonstrate that Type 2 A anatomy can occur without significant airway narrowing. The absence of tracheal stenosis in our patient—confirmed by both bronchoscopy and CT imaging—permitted a simplified surgical strategy consisting of isolated LPA reimplantation and ASD closure, without the added morbidity of tracheoplasty. Therefore, we advocate for routine bronchoscopic and CT evaluation to guide surgical planning, as the absence of intrinsic tracheal stenosis may allow for isolated vascular repair without tracheal intervention. This case provides evidence that anatomical subtypes can guide individualized surgical decision-making in patients with complex bronchovascular anomalies.

Conclusion

this case highlights that Bridging Bronchus (BB) and Pulmonary Artery Sling (PAS) should be considered in the differential diagnosis for children with recurrent respiratory symptoms. Multi-detector computed tomography (MDCT) with three-dimensional reconstruction serves as an ideal non-invasive tool for definitive diagnosis and preoperative planning, as it precisely delineates the complex tracheobronchial and vascular anatomy. Furthermore, follow-up MDCT is valuable for assessing postoperative outcomes (Fig. 6).

Fig. 6.

Postoperative pulmonary CTA with three-dimensional reconstruction, RPA(Right Pulmonary Artery), MPA(Main Pulmonary Artery), LPA - Left Pulmonary Artery

Authors’ contributions

Jianliang Liu conceptualized and designed the case report, and drafted the initial manuscript. Jie Song and Dongtao Li contributed to the case data curation, conducted literature review, and critically revised the manuscript for important intellectual content. Xiaojuan Pei and Yingjun Lu analyzed and interpreted the radiographic studies and critically reviewed the manuscript. Chunli Li and Jiajia Chen provided critical insights and assisted in the revision of the manuscript. As the corresponding author, Chengchang Liu supervised the entire project, performed a critical review and revision of the manuscript, and finalized the submission.All authors have read and approved the final version of the manuscript, and agree to be accountable for all aspects of the work.

Funding

This study received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Data availability

All data generated or analyzed during this study are included in this published article. The original imaging datasets are not publicly available to protect patient privacy but are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This study was conducted in accordance with the principles of the Declaration of Helsinki. The need for ethical approval was waived by the Ethics Committee of The First People's Hospital of Qinzhou for this retrospective case report. Written informed consent was obtained from the patient’s legal guardian(s) for both the surgical procedure and the participation in this study.

Consent for publication

Written informed consent for the publication of this case report and any accompanying images was obtained from the patient’s legal guardian(s). A copy of the written consent is available for review by the Editor-in-Chief of this journal.

Competing interests

The authors declare no competing interests.