Surg Radiol Anat DOI 10.1007/s00276-014-1383-6

ANATOMIC VARIATIONS

A case of bilateral tracheal bronchus: report of a rare association in multidetector computed tomography bronchoscopy Candace Wooten • Caius Doros • Gratian D. Miclaus Petru Matusz • Marios Loukas



Received: 13 March 2014 / Accepted: 7 October 2014 Ó Springer-Verlag France 2014

Abstract Bilateral tracheal bronchus is a rare variation of the tracheobronchial tree. We present a 1-year 7-month-old male patient who presented with sepsis following endotracheal intubation. Upon review of multidetector computed tomography images, the patient was diagnosed with displaced bilateral tracheal bronchus. Imaging showed a right-sided anomalous bronchus arising 0.9 cm proximal to the carina. The left-sided anomalous bronchus arose 0.7 cm proximal to the carina, mimicking a tracheal trifurcation. When viewed together, the close proximity of both the right and left tracheal bronchi to the carina created a distinct tracheal quadrifurcation. This rare anatomic variation was additionally associated with an anorectal malformation (anal atresia). Unrecognized tracheal bronchus in patients undergoing endotracheal intubation can lead to serious complications. While bilateral tracheal bronchus is described in the literature, we are unaware of any case similar to this patient presentation. We present C. Wooten Department of Family Medicine, University of Louisville, Louisville, KY, USA C. Wooten  C. Doros Department of ENT, ‘‘Victor Babes’’ University of Medicine and Pharmacy, Timisoara, Romania G. D. Miclaus  P. Matusz Department of Anatomy, ‘‘Victor Babes’’ University of Medicine and Pharmacy, Timisoara, Romania G. D. Miclaus Neuromed Diagnostic Imaging Centre, Timisoara, Romania M. Loukas (&) Department of Anatomical Sciences, St. George’s University, School of Medicine, Grenada, West Indies e-mail: [email protected]

and analyze this unusual case of bilateral tracheal bronchus. The anatomy and clinical significance of this variation is then discussed. Keywords Bilateral tracheal bronchus  Endotracheal intubation  Lower respiratory tract infection  Multidetector computed tomography (MDCT)  Threedimensional reconstruction  Virtual bronchoscopy

Introduction Tracheal bronchus was first described in 1785 by Sandifort as a variation of the tracheobronchial tree where the right upper lobe bronchus arises from the trachea, usually less than 2 cm above the carina [4, 5, 7]. The presence of a right tracheal bronchus is a normal finding in swine, cattle, camels, giraffes, goats, and sheep; however, it is a rare and usually incidental finding in humans [7]. Right tracheal bronchus has a prevalence of 0.1 % in the general population, while left tracheal bronchus has a prevalence of 0.3 % in bronchographic and bronchoscopic studies [1, 7]. Several studies have reported right-sided tracheal bronchus; however, very few cases of bilateral tracheal bronchus exist in the literature. In reports of bilateral tracheal bronchus, a consistent association with heterotaxy (asplenia) syndrome is also reported [5, 6, 8]. Right-sided tracheal bronchus has been associated with VACTERL syndrome (Vertebral defects, Anal atresia, Cardiac abnormalities, Tracheo-Esophageal fistula/atresia, Renal agenesis/dysplasia, Limb defects) in exactly two cases in the literature [2, 3]. We are unaware of any previous case of bilateral tracheal bronchus associated with isolated anal atresia. This case is even more unique due to the fact that the origin of the anomalous bronchi results in an

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anatomical presentation that mimicks a tracheal quadrifurcation. We present a unique case of bilateral tracheal bronchus associated with tracheal quadrifurcation and anal atresia. The anatomy and clinical significance of this variation of the tracheobronchial tree is then discussed.

Case report We report a 1-year 7-month-old male on mechanical ventilation who presented with sepsis, cough, and inspiratory stridor. This patient’s past medical history included multiple diagnoses of pneumonia resolved with antibiotic therapy, and his present hospital course involved multiple corrective surgical procedures for an anorectal malformation (anal atresia). His hospital course was complicated by the development of a lower respiratory tract infection and the eventual need for long-term ventilator support. After the insertion of the endotracheal tube, the patient began showing signs of sepsis. Radiographic examination revealed an obstructed right tracheal bronchus with concurrent right upper lobe consolidation. The cause of the obstruction was determined to be the placement of the endotracheal tube. The tube extended past the origin of the right tracheal bronchus thereby blocking its opening into the trachea. Given his history of respiratory complications, the patient was sent for multidetector computed tomography (MDCT) to assess the morphology of the respiratory tract. The examination was performed at the Neuromed Diagnostic Imaging Centre (Timisoara, Romania). Scanning was performed on a 64-slice multidetector CT scanner (SOMATOM Sensation, Siemens Medical Solutions, Forchheim, Germany). This was followed by three-dimensional reconstruction and virtual bronchoscopy. Imaging revealed a right-sided tracheal bronchus (displaced), with its lower edge 0.9 cm distant to the carina. The right tracheal bronchus measured 1.4 cm in length with a diameter of 0.4 cm at its origin, making an obtuse angle of 122° to the long axis of the trachea. A distance of 0.2 cm was measured between the adjacent edges of the right main stem and right tracheal bronchus, making an acute angle of 14°. The right anomalous bronchus gave rise to three segmental bronchi: apical segmental bronchus [BI], posterior segmental bronchus [BII], and an anterior segmental bronchus [BIII]. Imaging also revealed a left-sided tracheal bronchus (displaced), with its lower edge arising 0.7 cm distant to the carina. The left tracheal bronchus measured 1.3 cm in length with a diameter of 0.3 cm at its origin, making an acute angle of 59° with the long axis of the trachea. The left tracheal bronchus gave rise to a single segmental bronchus: a superior segmental bronchus of the lower lobe [BVI]. (Figs. 1, 2).

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Fig. 1 Three-dimensional MDCT reconstruction showing right tracheal bronchus (RTB) and left tracheal bronchus (LTB) arising in close proximity to the carina, depicting a tracheal quadrifurcation. Trachea (T), carina (C), right main bronchus (RMB), left main bronchus (LMB)

Fig. 2 Virtual bronchoscopic image showing origins of right tracheal bronchus (RTB), left tracheal bronchus (LTB), right main bronchus (RMB), left main bronchus (LMB), and carina (C)

Discussion The term tracheal bronchus encompasses several variants originating from the trachea or mainstem bronchus. A displaced tracheal bronchus, the most common

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presentation, refers to a bronchus being displaced from the usual trifurcation of the right upper lobe bronchus to the right lateral wall of the trachea. In these cases, the right upper lobe bronchus will have only two terminal branches, and the displaced bronchus will usually aerate that segment of the upper lobe which had to be supplied by the missing branch of the right upper lobe bronchus. Site of origin in the trachea is used to further classify these variants. A bronchus arising proximal to the origin of the upper lobe bronchus is called pre-eparterial on the right side and eparterial on the left side [10]. While the exact embryologic origin of this variant is undetermined, there exist three competing theories describing the development of tracheal bronchi. The reduction theory attributes these variants to a failure of bronchial bud regression in utero, the migration theory postulates a literal migration from the initial location to new points of origin on the bronchi or trachea, and the selection theory describes a resulting disturbance of normal embryogenesis [10]. This last theory is supported by the increase in incidence of other congenital anomalies in these patients, including heterotaxy (asplenia) syndrome and VACTERL syndrome [2, 3, 5, 6, 8]. Anal atresia, as seen in our patient, is a component of VACTERL syndrome. Multidetector computed tomography (MDCT) shows high sensitivity in the diagnosis of tracheobronchial variants. In a study by Ming and Ling [5], they reported a diagnostic sensitivity of 100 % with the use of MDCT to detect tracheal bronchus. Three-dimensional reconstruction is a useful tool for mapping the tracheobronchial system, especially when planning anesthetic and surgical procedures. Our patient was diagnosed to have bilateral displaced tracheal bronchus resulting in a tracheal quadrifurcation. The variant was further classified as a displaced pre-eparterial right tracheal bronchus plus a corresponding displaced eparterial left tracheal bronchus. Our data are consistent with previous reports with respect to the rightsided anomalous bronchus [5, 6, 8]. The unique nature of our case lies in the origin of the left tracheal bronchus. Its close proximity to the carina, combined with the location of the right tracheal bronchus, creates the appearance of a carinal quadrifurcation. While previous bilateral tracheal bronchi are usually located approximately, 2 cm distant to the carina, our patient’s tracheal bronchi are located between 7 and 9 mm distant to the carina. While Wong and Kumar [9] described a carinal trifurcation involving a right-sided tracheal bronchus, a case of bilateral tracheal bronchus resulting in carinal quadrifurcation is not described in the literature so far. Our patient also presented with an associated anal atresia, a component of VACTERL syndrome. Other VACTERL syndrome patients presenting a bronchial variant were diagnosed with

isolated right-sided tracheal bronchus [2, 3]. Our patient is the first to present isolated anal atresia with bilateral tracheal bronchus. This rare variation is typically asymptomatic; however, it can cause complications during endotracheal intubation [9]. Patients undergoing endotracheal intubation are at risk of occlusion of the lumen of the tracheal bronchus. Unrecognized malposition of the endotracheal tube can result in hypoventilation of the lobe supplied by the anomalous bronchus and intraoperative hypoxemia [9]. Furthermore, post-obstructive pneumonia can lead to sepsis, as was seen in our patient. Placement of the endotracheal tube directly into the lumen of the tracheal bronchus can result in inadequate ventilation of the rest of the respiratory system. Since a tracheal bronchus could potentially originate from any part of the trachea, there is no recommendation of a standard distance to place the endotracheal tube that could prevent obstruction. The most efficient way to prevent this complication is proper physician training in the recognition of these variants and routine chest radiographs to ensure proper endotracheal tube placement. While tracheal bronchus occurs in a small portion of the population, there are severe consequences for this unrecognized variant in a critical care setting. Prior awareness of this anatomic variation is important in caring for the critically ill. Therefore, cases of challenging endotracheal intubation should always include the differential diagnosis of tracheal bronchus. Conflict of interest of interest.

The authors declare that they have no conflict

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Surg Radiol Anat tomographic findings of bilateral tracheal bronchus. Pediatr Cardiol 30(1):87–88 9. Wong DT, Kumar A (2006) Case report: endotracheal tube malposition in a patient with a tracheal bronchus. Can J Anaesth 53(8):810–813

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10. Wooten C, Patel S, Cassidy L, Watanabe K, Matusz P, Shane Tubbs R, Loukas M (2014) Variations of the tracheobronchial tree: anatomical and clinical significance. Clin Anat. doi: 10.1002/ca.22351 [Epub ahead of print]

A case of bilateral tracheal bronchus: report of a rare association in multidetector computed tomography bronchoscopy.

Bilateral tracheal bronchus is a rare variation of the tracheobronchial tree. We present a 1-year 7-month-old male patient who presented with sepsis f...
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