Tracheobronchial stenting in an infant with an anomalous right main bronchus.

Abstract

Congenital anomalies of the right main bronchi have not been fully described. Bronchial anomalies are usually asymptomatic unless they coexist with other abnormalities. We describe a rare bronchial anomaly in a 2-month-old girl in which the right upper lobe, middle lobe, and lower lobe bronchi all originated at the same point as a result of a developmental teratogenic long right main bronchus and an absent bronchus intermedius. Furthermore, the left main bronchus contained a proximal segment of stenosis. This combination of anomalies, along with right upper lobe atelectasis and left-sided hyperinflation, resulted in a severe right mediastinal shift and respiratory distress. The mediastinum was returned to midline with endoscopic placement of an in-dwelling tracheobronchial stent into the left main bronchus. To the best of our knowledge, the specific developmental anomaly in our patient has not been previously described.

Introduction

The embryonic period encompasses the first 8 weeks of human development; the Carnegie system classifies this period into 23 stages or levels of development. (1) The fetal period represents the following 32 weeks of development. Throughout both stages, the exact age and size of the embryo/fetus are not known; instead, age and size are approximated.

* By stage 10 of the embryonic period (circa 22 days), the embryo is 2.0 to 3.5 mm long at its greatest dimension. The embryonic pharynx is a distinct entity, and a laryngotracheal sulcus and pulmonary primordium have formed.

* At stage 11 (ca. 24 days), the embryo is 2.5 to 4.5 mm long, and the respiratory primordium divides into the fight and left lobes.

* At stage 12 (ca. 26 days), the embryo is 3.0 to 5.0 mm long. During this stage, the "respiratory tap is turned on," (2) the tracheoesophageal separation point is definite, and the respiratory and digestive tracts develop separately.

* During stage 13 (ca. 28 days, 4 to 6 mm), the respiratory diverticulum, trachea, and the right and left lung buds are evident.

* During stage 14 (ca. 32 days, 8 mm) and stage 15 (ca. 33 days, 7 to 9 mm), the bronchial tree develops and the lung buds elongate.

* The lobar buds are present at stage 16 (ca. 37 days, 8 mm).

* The tracheal precartilaginous condensation is evident with segmental bronchial buds at stage 17 (ca. 44 days, 9 to 11 mm).

The scientific explanation of anomalies is related to the timing sequence of normal embryologic development. Based on these embryologic stages, the time frame when a teratogenic effect occurs may be identified, but the etiology may not be determined.

In this article, we describe a rare bronchial anomaly in an infant whose right upper lobe, middle lobe, and lower lobe bronchi all originated at the same point. The anomaly was estimated to have occurred during stages 13 to 16 (ca. 28 to 37 days). This and other anomalies contributed to a severe right mediastinal shift and respiratory distress that were successfully treated with endoscopic placement of an in-dwelling tracheobronchial stent into the left main bronchus.

Case report

A 2-month-old girl was admitted with inspiratory stridor and respiratory distress. The stridor had been first noted 2 days following her birth, and it progressively worsened prior to admission. The infant had a breathy cry, cough, and perioral cyanosis with feedings. She was one of two twins delivered via cesarean section at 37 weeks.

Barium swallow examination revealed tracheal aspiration, and gastroesophageal reflux was later confirmed with a milk scan. Awake flexible fiberoptic laryngoscopy revealed pharyngeal hypotonia and poor vocal fold mobility. The epiglottis was well supported without evidence of laryngomalacia. By direct laryngoscopy, the cricoarytenoid joint was passively manipulated without restriction, and the dimension of the subglottis was adequate for passage of a 4-mm Hopkins rod telescope. There was no evidence of a laryngeal cleft or other laryngeal anomaly. Magnetic resonance imaging (MRI) of the brain ruled out ArnoldChiari malformation and hydrocephalus as a cause of the vocal fold paresis.

The following day, tracheotomy, Nissen fundoplication, and gastric tube placement were performed, and the patient remained on the ventilator postoperatively. The option of a prolonged intubation for this infant was not entertained in view of the risk of subglottic stenosis, the severity of her symptoms, and the need for pulmonary toilet after aspiration of the barium.

On postoperative day 3, patchy atelectasis of the right lung was noted on chest roentgenography. By postoperative day 9, the left side had become hyperinflated, which resulted in a right mediastinal shift (figure 1). The possibility of a left-sided mucous plug was considered as the etiology, and aggressive suctioning was performed. This resulted in improvement of the patient's condition, and she was subsequently weaned off the ventilator and discharged home.

[FIGURE 1 OMITTED]

Several hours after discharge, however, the infant was readmitted with recurrent respiratory distress. She was treated medically with nebulized albuterol, which initially alleviated her wheezing and respiratory effort, but her symptoms soon after worsened. Ipratroprium was then initiated, and she experienced mild improvement. A new chest roentgenogram again showed left-sided hyperinflation and a shifting of the mediastinum to the right. Opentube rigid bronchoscopy detected a pulsatile stenosis in the anterosuperior segment of the left main bronchus; the distal anatomy was normal. A tracheal bronchus was not identified. Dilation of the left malnbronchus was performed with a 4-mm Hopkins rod telescope.

MRI of the heart and mediastinum ruled out vascular compression of the left main bronchus. However, an aberrant right subclavian artery was identified coursing posterior to the esophagus. The aorta appeared to be compressing the left main bronchus in the anterosuperior quadrant. Computed tomography (CT) of the chest showed that the right main bronchus was elongated. A lung perfusion scan demonstrated poor perfusion to the left lobe (25.3% uptake of technetium-99) and increased perfusion of the right lung (74.7% uptake).

Within 48 hours, the patient deteriorated clinically, and significant mediastinal shifting recurred despite dilation. Continuous positive airway pressure was instituted in an attempt to maintain patency of the left main bronchus, but no clinical improvement ensued. Therefore, a tracheobronchial stent was endoscopically placed into the left main bronchus to assure its patency. This stent, which was first described by Davis et al, (3) was fashioned by using a 3.5 Shiley pediatric tracheostomy tube as a collar and placing a 3.0 endotracheal tube through it (figure 2). An additional ventilation port was placed in the endotracheal tube at the level of the carina tracheae to ventilate the right lung. The stent was placed endoscopically within the left main bronchus via the tracheotomy site with the aid of a 2.5-mm Storz telescope functioning as an optical stylet. Complete resolution of the mediastinal shift occurred.

[FIGURE 2 OMITTED]

Removal of the stent resulted in a gradual return of the mediastinal shift. Repeat awake fiberoptic laryngoscopy revealed less hypotonia and bettervocal fold mobility. Rigid bronchoscopy revealed an anomalous distal positioning of the right lung segmentations and a marked circumferential stenosis of the left main bronchus. The stenotic area was not pulsatile during this procedure, and it was easily bypassed with a 4-mm Hopkins rod telescope. The distal portion of the left lung was normal. The stent was replaced, and the mediastinum returned to the midline.

Bronchography demonstrated a long right main bronchus and the apparent absence of a bronchus intermedius (figure 3). The right upper lobe branch originated from the right main bronchus at approximately the same level as the right middle and lower lobe bronchi. Stenosis of the left main bronchus was circumferential, and normal distal branching was confirmed.

[FIGURE 3 OMITTED]

Cardiac catheterization in conjunction with airbronchography showed a normal heart, an aberrant right subclavian artery, and a high bifurcation of the trachea at the level of the transverse aortic arch. The right upper and middle lobes were small in comparison with the right lower lobe.

Stent removal was attempted several times when smallairway function was maximized and secretions were minimal. With every trial, the infant was able to maintain good oxygen saturation without a stent for longer periods. The stent was eventually removed after having been in place for a total of 101 days. Upon its removal, the left main bronchus remained patent.

At follow-up, the infant was maintained on only a tracheostomy tube because of her underlying chronic lung disease, and she was able to tolerate oral feedings without aspiration.

Discussion

Pulmonary dysgenesis in the presence of a partial or complete bronchial tree may be associated with the absence of alveoli. The condition is usually unilateral and compatible with life, although it was life threatening in the case described here. Agenesis and dysgenesis have been attributed to a lack of developmental balance between the right and left lung buds rather than to merely an arrest in their development. (4)

Bronchial variability is more common in the upper lobes and on the right side. Our patient had an anomaly that to the best of our knowledge has not been previously described. The mediastinal shifting may have been a result of the combined effect of atelectasis secondary to the anomalous branching of the right lung and the stenotic left main bronchus, which can be attributed to bronchomalacia. Jacobs et al reported that tracheobronchomalacia is a common airway abnormality found in 15% of diagnostic bronchoscopies. (5) Primary tracheobronchomalacia is a rare congenital weakness of the cartilage of the airway. Secondary tracheobronchomalacia occurs with degeneration of previously normal cartilaginous support. This can occur in infants with respiratory distress syndrome, recurrent infections, and peripheral-airway obstruction. As was the case with our patient, patients with large-airway obstruction will not respond to inhaled beta-agonists or steroids. Patients with both large- and small-airway obstructions may intermittently respond to beta-agonists when the small-airway obstruction predominates; on the other hand, they may experience a worsening of symptoms when large-Airway obstruction predominates. Tracheobronchomalacia is usually self-limited, and most cases resolve by the time the patient reaches 6 months of age. The placement of the tracheobronchial stent in our patient provided patency of the large airway while allowing the tracheobronchial tree time to mature and stiffen.

Stenting in children is clearly more challenging because of the small dimensions of their tracheobronchial tree. Moreover, data involving long-term follow-up are lacking. Filler et al reported favorable results with the use of balloon-expandable metallic Palmaz stents; the most common complications were stent migration and the development of obstructive granulation tissue. (6) On the other hand, Furman et al used the same stent in their series and reported 2 deaths. (7)

The Gianturco metallic Z stent was used by Bugmann et al with good results initially, but complete mucosalization occurred within 15 days, which made stent removal difficult. (8) Campbell et al (9) and Brooks et al (10) described selective bronchialintubation in infants with pulmonary emphysema; the period of intubation ranged from 1 to 10 days. The main advantages of the stenting technique we used include the ease and accuracy with which it can be placed, repositioned, and removed. The only problems that we encountered were a small amount of granulation tissue, which is to be expected with an in-dwelling stent, (11) and stent migration. However, the granulation tissue was nonobstructing, and the stent was easily adjusted via endoscopic guidance without posing a risk that it would become embedded in the walls of the bronchus. Davis et al have documented the use of this stent for external compression secondary to congenital vascular anomalies. (3) We further advocate this stent for use in infants with segmental bronchomalacia when long-term endobronchial stenting is required or when corrective surgery is not advisable.

References

(1.) O'Rahilly R, Boyden EA. The timing and sequence of events in the development of the human respiratory system during the embryonic period proper. Z Anat Entwicklungsgesch 1973;141:237-50.

(2.) O'Rahilly R, Muller E Chevalier Jackson lecture. Respiratory and alimentary relations in staged human embryos. New embryological data and congenital anomalies. Ann Otol Rhinol Laryngol 1984;93:421-9.

(3.) Davis DA, Tucker JA, Russo P. Management of airway obstruction in patients with congenital heart defects. Ann Otol Rhinol Laryngol 1993;102:163-6.

(4.) O'Rahilly R, Muller F. Human Embryology & Teratology. New York: Wiley-Liss; 1992.

(5.) Jacobs IN, Wetmore RF, Tom LW, et al. Tracheobronchomalacia in children. Arch Otolaryngol Head Neck Surg 1994;120:154-8.

(6.) Filler RM, Forte V, Chait P. Tracheobronchial stenting for the treatment of airway obstruction. J Pediatr Surg 1998;33:304-11.

(7.) Furman RH, Backer CL, Dunham ME, et al. The use of balloon-expandable metallic stents in the treatment of pediatric tracheomalacia and bronchomalacia. Arch Otolaryngol Head Neck Surg 1999;125:203-7.

(8.) Bugmann P, Rouge JC, Berner M, et al. Use of Gianturco Z stents in the treatment of vascular compression of the tracheobronchial tree in childhood. A feasible solution when surgery fails. Chest 1994;106:1580-2.

(9.) Campbell AN, Zarfin Y, Perlman M. Selective bronchial intubation for pulmonary emphysema. Arch Dis Child 1984;59:890-2.

(10.) Brooks JG, Bustamante SA, Koops BL, et al. Selective bronchial intubation for the treatment of severe localized pulmonary interstitial emphysema in newborn infants. J Pediatr 1977;91:648-52.

(11.) Albert DM, Hartley BE, Roebuck D. Contemporary concepts in the evaluation and management of tracheobronehomalacia in children. Current Opinion in Otolaryngology and Head Neck and Surgery 2001 ;9:346-51.

Kalpana S. DePasquale, DO; John A. Tucker, MD; Barbara Wolfson, MD; Laurie Varlotta, MD

From the Department of Otolaryngology, Flagler Hospital, St. Augustine, Fla. (Dr. DePasquale); the Department of Otorhinolaryngology-Head and Neck Surgery, University of Pennsylvania School of Medicine, Philadelphia (Dr. Tucker); and the Department of Radiology (Dr. Wolfson) and the Pediatric Pulmonary Center (Dr. Varlotta), St. Christopher's Hospital for Children, Philadelphia.

Reprint requests: Kalpana S. DePasquale, DO, Attending Physician, Department of Otolaryngology, Flagler Hospital, 1301 Plantation Island Dr., Suite 401, St. Augustine, FL 32080. Phone: [phone]; fax: [phone]; e-mail: [e-mail]