Introduction

Congenital tracheal stenosis (CTS) is a rare and challenging pediatric condition frequently associated with other airway or cardiovascular anomalies [1,2,3]. Complete tracheal rings cause a wide spectrum of airway-obstructing lesions and varying degrees of respiratory distress [1, 2, 4, 5]. Surgical and endoscopical techniques developed in recent decades have dramatically improved the outcome of patients with CTS [2, 3]. However, while patients with severe stenosis may need urgent treatment because of life-threatening airway obstruction, not every patient with CTS requires operative treatment considering operative mortality [2, 4, 5]. The decision toward operative repair is based on the severity of symptoms and the patient’s comorbid conditions [4]. Sometimes formulation of an appropriate management strategy may be difficult due to associated anomalies.

Methods

After Institutional Review Board approval (A18-012), we examined pediatric patients with CTS diagnosed in our institution between June 2007 and December 2017. A retrospective study was conducted to identify pitfalls in the management of CTS with associated other anomalies.

Results

Sixteen patients with CTS were diagnosed via rigid bronchoscopy and contrast-enhanced computed tomography (CT) during the observation period. The demographics, including types of CTS, and treatment and outcomes of patient with CTS are summarized in Table 1. Complete tracheal rings were observed in all patients and caused various degree of respiratory symptoms. There were eight male and eight female patients. The median age at diagnosis was 2.5 months (range 4–10 years). The median weight at diagnosis was 3.8 kg (range 1.6–35.4 kg). Of the 16 patients, 12 (75.0%) had cardiovascular anomalies including seven left pulmonary artery sling diagnosed via echocardiography and CT; three patients had unilateral pulmonary agenesis or hypoplasia; two patients had trisomy 21; one patient had anorectal malformation and biliary atresia.

Table 1 Patient with CTS: demographics, types of CTS, treatment and outcomes
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Among the 12 patients with cardiovascular anomalies, three patients with severe dyspnoea underwent tracheal reconstruction simultaneously with cardiac surgery through a median sternotomy with the use of cardiopulmonary bypass (Pt. 1–3); two patients underwent balloon tracheoplasty for the purpose of intubation before cardiac surgery (Pt. 4, 5); one patient underwent left pulmonary artery reimplantation without tracheoplasty (Pt. 6); two patients who had severe respiratory problems recovered by other than tracheoplasty (Pt. 7, 8); and four patients without respiratory distress were followed up without undergoing any surgical procedure (Pt. 9–12). Among the four patients without cardiovascular anomalies, CTS repair was performed in all four patients. Two patients with dyspnoea underwent tracheal reconstruction (Pt. 13, 14). One patient suffered from repeated aspiration pneumonia with West syndrome underwent tracheostomy simultaneously with tracheal reconstruction (Pt. 15). Two neonatal patients with severe dyspnoea underwent balloon tracheoplasty (Pt. 14, 16).

Except for one neonatal patient who died of tracheal bleeding on fifth day after tracheoplasty (Pt. 3), all surgical patients were weaned off the ventilator or extubated. One patient died suddenly with unknown cause 2 years after balloon tracheoplasty (Pt. 16). Non-surgical patients were alive and in good respiratory condition.

Four patients with especially complex pathophysiology (Pt. 5–8) were the focus of this study. Although the examinations with rigid bronchoscopy and CT indicated mild CTS, they experienced repeated episodes of severe respiratory failure. We discussed the etiology of their complications at multidisciplinary team meetings and recommended the best treatment strategies. The clinical courses of these four patients are described in detail below.

Patient 5

A 1-month-old boy weighing 3.5 kg was referred to our hospital because of CTS associated with double-outlet right ventricle/pulmonary atresia/patent ductus arteriosus. He initially had no respiratory distress. Distal trachea was slightly narrowed with a short segment of circular rings. He received a modified Blalock–Taussig shunt after balloon tracheoplasty and forced intubation (Fig. 1a, b). Owing to postoperative tracheomalacia, he could not be extubated and received a tracheostomy at 4 months of age. However, his recurrent cyanotic episodes continued due to crying-induced right ventricular outflow tract obstruction and consequent anoxia. Since bronchoscopy at 2 years and 1 months of age revealed improvement of both CTS and tracheomalacia, he underwent open-heart surgery without concomitant CTS repair. After intracardiac repair, his respiratory condition improved and stabilized.

Fig. 1
figure 1

Balloon tracheoplasty and forced intubation preceded initial cardiac surgery in patient 5. Fluoroscopic balloon dilatation for tracheal stenosis (a) and contrast bronchography after balloon tracheoplasty (b)

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Patient 6

A 6-month-old girl weighing 5.6 kg without respiratory distress visited us as an outpatient. She had been diagnosed with CTS associated with pulmonary artery sling during hospitalization for acute pneumonia at another hospital. Rigid bronchoscopy and CT at 7 months of age demonstrated mild and focal tracheal stenosis with complete cartilage rings, compression of the left bronchus by the left pulmonary artery, and hypoplasia of the right lung. A recurrent respiratory infection worsened her condition, and episodes of a “dying spell” made extubation difficult. Left bronchial malacia due to pulmonary artery sling rather than CTS presumably accounted for her respiratory failure. Left pulmonary artery reimplantation was performed when she was 11 months old. We decided to forego tracheal reconstruction and aortopexy because intraoperative bronchoscopy confirmed the patency of the trachea and the left bronchus after pulmonary artery sling repair (Fig. 2a, b). 3-D MDCT also visualized that compression of the left main bronchus was released after left pulmonary artery reimplantation (Fig. 3a–c). The patient was extubated after plication of the left hemi-diaphragm, which was elevated due to left phrenic nerve palsy. She is now 3 years and 11 months old and in good condition.

Fig. 2
figure 2

Intraoperative bronchoscopy confirmed the patency of the left bronchus in patient 6. a The left main bronchus (black arrow) was compressed. b The lumen of the left main bronchus (black arrow) was dilated after left pulmonary reimplantation

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Fig. 3
figure 3

3-D MDCT examined pre- (a, b) and (c) post-left pulmonary artery reimplantation visualized respiratory tract and vascular anomalies in patient 6. a, b CTS (white arrowhead) was mild and the left pulmonary artery (asterisk) compressed the left main bronchus (black arrow). c The compression of the left main bronchus (white arrow) was released after left pulmonary artery (asterisk) reimplantation. Tracheal reconstruction was not performed (white arrowhead)

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Patient 7

A 1-month-old girl weighing 2.9 kg was referred to our hospital because of respiratory problems, difficulty of extubation, and poor weight gain. She was diagnosed with CTS, a ventricular septal defect (VSD), and an atrial septal defect (ASD) at another hospital. Rigid bronchoscopy and CT revealed mild and focal stenosis of distal trachea with complete cartilage rings, a right tracheal bronchus, and right lung hypoplasia. The main cause of her respiratory failure appeared to be severe heart failure with increased pulmonary blood flow. Continuation of conservative management for chronic heart failure was difficult, and pulmonary artery banding was performed when she was 7 months old and weighed 2.6 kg. After the operation, the patient slowly gained weight. Open-heart surgery was performed to close the VSD and ASD when she was 1 year and 10 months old and weighed 7.8 kg. She is now 2 years and 1 month old and has no respiratory distress on home oxygen therapy (flow rate 0.25 L/min) prescribed for heart failure.

Patient 8

A 1-month-old girl weighing 2.5 kg was referred to our hospital because of complete atrioventricular septal defect and heart failure with increased pulmonary blood flow. Even after pulmonary artery banding, extubation was difficult with associated focal-type CTS involving the carina and right main bronchus, and thoracic insufficiency syndrome with left pulmonary hypoplasia (Fig. 4). She needed to wait for her body weight to increase before intracardiac repair with/without tracheal reconstruction. Since her respiratory condition was substantially stable during intubation proximal to the narrow segment, we considered that failed extubations were due to gastroesophageal reflux and subsequent pulmonary aspiration. She was extubated successfully after Nissen fundoplication at 1 year of age. Since bronchoscopy revealed improvement of CTS, she underwent open-heart surgery without concomitant CTS repair at 2 years of age and weighed 10.4 kg.

Fig. 4
figure 4

CT revealed CTS involving the carina (white arrowhead) and right main bronchus (black arrow), and thoracic insufficiency syndrome with left pulmonary hypoplasia in Patient 8

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Discussion

We described 16 patients with CTS diagnosed in our institution. Indications for surgical treatment were respiratory distress and difficult intubation before surgery for associated conditions. Six patients with dyspnoea caused by CTS and three patients with difficult intubations due to CTS underwent tracheoplasty. Four patients underwent only cardiovascular surgery without tracheoplasty. Three asymptomatic patients were followed up without undergoing any surgical procedure. Balloon tracheoplasty was mainly performed as initial airway management for neonates and small infants, and tracheal reconstruction as radical therapy for infants. One patient with severe respiratory distress underwent balloon tracheoplasty during the neonatal period, and followed by subsequent tracheal reconstruction during the infantile period (Pt. 14). On the other hand, one patient did not require further operation after balloon tracheoplasty during the neonatal period, because the diameter of stenotic region well increased over the years (Pt. 4). Overall outcome was mostly good in our experience. Many patients with cardiovascular anomalies were found incidentally on imaging studies and managed conservatively without surgical procedure, whose CTS was mild defined as asymptomatic or occasional respiratory symptoms and more than 50% diameter of a normal segment or more than a diameter of 4 mm in small infants.

CTS is associated with complete tracheal rings, which obstruct airways to varying degrees and produce symptoms of varying severity [2]. In 1964, Cantrell and Guild [1] described three forms of CTS: generalized, funnel-shaped, and focal. In 2003, Anton-Pacheco et al. [2] proposed a CTS classification system based on clinical aspects, endoscopic findings, and associated anomalies. From a clinical standpoint, the respiratory symptoms of CTS can be envisioned as a spectrum of malformations, including complete tracheal rings, pulmonary artery sling, and cardiovascular anomalies. Bronchoscopy is an essential tool for diagnosing CTS [2], and multidetector CT (MDCT) with 2-D or 3-D reconstruction facilitates CTS diagnosis in pediatric patients by accurately measuring tracheal narrowing. MDCT also provides information about other congenital anomalies [6].

Surgery is indicated in symptomatic cases of CTS. Standard surgical methods that produce good results include tracheal resection with end-to-end anastomosis for short-segment stenosis (less than 50% total tracheal stenosis) and slide tracheoplasty for long-segment stenosis (more than 50% total tracheal stenosis) [2, 3]. We previously described the use of balloon tracheoplasty as an initial treatment for neonates with CTS [7]. Surgery may not be required in asymptomatic cases of mild stenosis [4, 5, 8]. Cheng et al. [9] found that stenotic regions of the trachea increased in diameter more rapidly than normal regions in conservatively managed patients, especially after infancy. They suggested that the management of CTS should be individualized and that conservative management in a carefully selected subgroup of CTS is feasible and safe.

Four patients we focused on in this study had complicated pathophysiology. We repeatedly discussed their management at multidisciplinary meetings. The acute respiratory distress of these patients was mainly caused by associated other anomalies rather than CTS per se. Right ventricular outflow tract obstruction, tracheobronchial malacia, increased pulmonary blood flow, and pulmonary aspiration due to gastroesophageal reflux presumably accounted for their repeated respiratory distress. There were discrepancies between the degree of CTS and the patients’ symptoms, and formulation of an appropriate management strategy was difficult, especially with regard to the timing of cardiovascular surgeries and tracheoplasty. We performed balloon dilatations in one patient, but none of the patients required tracheal reconstruction.

The management of CTS complicated by cardiovascular anomalies is challenging. Although there are some reports of successful concomitant surgical repair of CTS and cardiac anomalies in infants [8, 10,11,12], the management strategy for CTS with cardiovascular anomalies remains controversial. When CTS appears mild, the need for and timing of surgical procedures for CTS is especially unclear. In our cases, severe respiratory symptoms due to cardiovascular anomalies caused confusion about the prognosis of CTS, and we were forced to make a difficult decision of whether we should perform tracheal reconstruction during the cardiovascular surgery or not. CT and bronchoscopy provided objective accurate information about CTS and the accompanying anomalies. It was important to remove factors affecting respiratory symptoms one by one. Conservative management or stepwise surgery is reasonable in selected cases with mild CTS.

The limitations of this study are the small sample size and a short follow-up period. We should continue to observe our patients carefully. Loukanov et al. [13] reported that progressive, funnel-type CTS eventually required surgery and strongly recommend tracheal reconstruction. In our opinion, balloon dilatation may be a rescue treatment for mild CTS, even if surgical tracheal repair is required after cardiovascular operation via thoracotomy.

Conclusion

We usually manage patients with CTS based on their clinical symptoms, which provide good results. However, we occasionally observe discrepancies between the respiratory symptoms and the degree of CTS in cases accompanied with cardiovascular anomalies. Surgical treatment should be planned for each patient according to objective evaluation (e.g., via CT and intraoperative bronchoscopy) and using a multidisciplinary approach. Careful conservative management of CTS is also a feasible option in selected cases.