Tracheobronchial variations evaluated by multidetector computed tomography and virtual bronchoscopy

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Licensee OA Publishing London 2013. Creative Commons Attribution License (CC-BY)

For citation purposes: Vassiou K, Kotrogianni F, Lavdas E, Vlychou M, Fanariotis M, Arvanitis DL, et al. Tracheobronchial variations evaluated by multidetector computed tomography and virtual bronchoscopy. OA Case Reports 2013 Mar 01;2(3):23. Co

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Tracheobronchial variations evaluated by multidetector computed tomography and virtual bronchoscopy

K Vassiou1, F Kotrogianni2, E Lavdas3, M Vlychou4, M Fanariotis4,DL Arvanitis1, IV Fezoulidis4*

AbstractIntroductionThe tracheobronchial tree exhibits a wide range of variations. The pur-pose of this study is the investigation of the frequency and multidetec-tor tomographic (MDCT) findings of anatomical variations of the main bronchi and of the lobar bronchi, as well as the detection of abnormal bronchi originated from the trachea, in subjects without severe bronchial pathology.Materials and methodsAbout 872 consecutive patients who underwent thoracic MDCT examina-tion were enrolled in the study. All MDCT data, including multiplanar reconstructions, maximum intensity projections and volume-rendered images, as well as virtual bronchos-copy, were evaluated for the detec-tion of main bronchial variations. Various kinds of bronchial variations and anomalies, such as tracheal bron-chus, accessory cardiac bronchus, bronchus hypoplasia and bronchial origin anomalies, were documented.ResultsIn 872 subjects, the overall frequency of main bronchus variations is 2.52% (22/872). More specifically, tracheal

bronchus were found in eight cases (0.9%), accessory cardiac bronchus was found in one case (0.1%), hypo-plasia was found in one case (0.1%) and bronchial origin anomalies were found in 10 cases (1.14%).ConclusionThe display of tracheobronchial vari-ations is of clinical importance first because they are related to infections and, sometimes, malignancies and second in preoperative or in cases of bronchoscopic procedures. In our study, the commonest variation was the tracheal bronchus. MDCT and virtual bronchoscopy can depict tra-cheobronchial variations accurately and can be served as an alternative to bronchoscopy in certain cases of possible bronchial anomaly.

IntroductionTracheobronchial tree variations (TBVs) are a rare clinical entity in-cluding anomalies of the main bron-chus or abnormal bronchi originated from the trachea and anatomic vari-ations of the lobar, segmental and subsegmental bronchi. The most common main bronchus anomalies are the tracheal bronchus and the accessory cardiac bronchus. Other bronchial anomalies include dis-placed or supernumerary segmental bronchi and bronchial agenesis.

Recognition and reporting of the TBV is important, as they are associ-ated with clinical complications, such as episodes of infection, hemoptysis and perhaps malignancies in a small percentage of patients1.

Multidetector computed tomogra-phy (MDCT) with multiplanar recon-structions (MPRs) provides a precise investigation of the lung and the

tracheobronchial tree2. Computed tomography (CT) virtual bronchos-copy (VB) is a three-dimensional (3D) technique that is used as an adjunct to MDCT because it provi des endobronchial evaluation of the tracheobronchial tree.

In this study, we present our ex-perience on congenital bronchial anomalies concerning the main lobe bronchi in adults with no acquired deformity of the tracheobronchial tree, their MDCT and VB findings, and discuss the most common variation at our study population.

Materials and methodsThis work conforms to the values laid down in the Declaration of Helsinki (1964). The protocol of this study has been approved by the relevant ethi-cal committee related to our institu-tion in which it was performed. All subjects gave full informed consent to participate in this study.

Patient populationOver a 1-year period, 872 consecu-tive patients (521 men and 351 women; age range, 20–78 years; mean age, 54 years) who underwent thorax MDCT examination were eval-uated for detection of bronchial vari-ations and anomalies. Indications for thorax MDCT examinations were the evaluation of lung opacities de-tected on chest radiography, the in-vestigation of primary lung tumours or vascular and airway pathologies, the follow-up of known pulmonary lesions and the follow-up of primary tumours anywhere else but the lung. Exclusion criteria were major surgi-cal procedures that alter the bron-chial anatomy or severe bronchial

* Corresponding author Email: [email protected] Department of Anatomy, Faculty of Medicine,

School of Health Science, University of Thessaly, Larissa, Greece

2 Faculty of Medicine, School of Health Science, University of Thessaly, Larissa, Greece

3 Departement of Medical Radiological Technologists, Technological Education Institute of Athens, Greece

4 Department of Radiology, Faculty of Medicine, School of Health Science, University of Thessaly, Larissa, Greece

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For citation purposes: Vassiou K, Kotrogianni F, Lavdas E, Vlychou M, Fanariotis M, Arvanitis DL, et al. Tracheobronchial variations evaluated by multidetector computed tomography and virtual bronchoscopy. OA Case Reports 2013 Mar 01;2(3):23. Com

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variations. Also, anatomic variations were demonstrated by CT VB.

ResultsIn our study, 22 cases (2.52%) with TBVs were identified. Fourteen of these (70%) were detected in males and eight (30%) were detected in females. TBVs were more frequent at the right bronchus (19/22, 86.3%).

Eight cases (0.9%) had tracheal bronchus. All of them were defined as right pre-eparterial. In three cas-es, the right pre-eparterial bronchi were arising from the junction be-tween the trachea and carina, while in the remaining cases they were arising from the right main bronchus ( Figure 1). In five cases, the bronchi were of the displaced type, and in three cases they were of the super-numerary type (Figure 2).

In one case, right accessory car-diac bronchus was found (0.1%) ( Figure 3) and in another case hy-poplastic right upper lobe bronchus (0.1%) was seen (Figure 4). Four cases were found (0.45%) with com-mon origin of the right upper and middle lobe bronchus, two cases (0.22%) with origin of the right mid-dle lobe bronchus from the right lower lobe bronchus and three cases with aplasia of the right middle lobe bronchus (0.34%) (Figure 4). In four cases (0.45%), the origin of the left lingual lobe bronchus was from the left lower lobe bronchus.

DiscussionIn large bronchoscopic studies, ana-tomical variations of the tracheobron-chial system are reported as 1–12%2. Knowledge of tracheobronchial anatomy is of importance in cases of bronchoscopic processes, pulmonary surgery, intubation or other inter-ventional procedures. TBVs may be associated with other abnormalities or clinical symptoms1,3–5 and may re-quire interventional procedures.

TBVs are demonstrated in large se-ries by bronchoscopy6–8. To our knowl-edge, there are a number of studies

scan was acquired 30 s after the initiation of the injection (arterial phase).

Image analysisPost-processing of the data was per-formed on a dedicated diagnostic workstation (Vitrea, Toshiba Medical Systems, Otawara, Japan). In all sub-jects, axial, sagittal, coronal MPRs, minimal and maximum intensity pro-jection (MinIP, MIP) images were ob-tained. In addition, volume- rendered (VR) images were created with the opacity curve manipulated to remove all structures but the lung–air inter-face. Two radiologists evaluated all images at the same time in consen-sus for the presence of tracheal and bronchial anatomic anomalies and

pathology that prevent the accurate bronchial detection.

MDCT protocol CT imaging was performed on a 16- row multidetector scanner (Aquilion 16, Toshiba Medical Sys-tems, Otawara, Japan). All patients were scanned in the supine position using a breath-hold technique. Scanning parameters were as fol-lows: 120 kVp, 60–90 mAs, 0.5 gan-try rotation time, pitch 0.9, scan slice thickness 1mm × 16, recon-structed at 1 mm, average scan time 15 s. An automatic power injection was used to administer intrave-nously a 100 ml bolus of 300 mg/ml nonionic iodinated contrast ma-terial at a rate of 3.2–3.5ml/s. The

Figure 1: Right pre-eparterial bronchus. (a) Coronal MPR shows the tracheal bronchus (arrow) arising from the right main bronchus below the level of the carina. (b) Coronal MPR shows the tracheal bronchus (arrow) arising at the level of the carina. (c) Virtual bronchoscopy (VB) image shows the tracheal bronchus (thin arrow) completely splitting from the right upper lobe bronchus (large arrow) arising at the level below the carina (asterisk). (d) Volume-rendered (VR) 3D image clearly showing the main bronchi of the tracheobronchial tree and the right pre-eparterial bronchus (arrow).

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Figure 2: Different types of tracheal bronchus. (a) Virtual bronchoscopy (VB) image shows displaced right tracheal bronchus (arrow). The right upper lobe bronchus splits into two segmental bronchus (asterisks) and one branch of the upper lobe bronchus is missing. (b) Coronal MPR shows a supernumerary right tracheal bronchus (arrow). The right upper lobe bronchus normally splits into three segmental bronchus.

Figure 3: Coronal MPR shows right accessory cardiac bronchus (arrow).

Although anatomical variations of the lobar and subsegmental bronchi are relatively common, anomalies of the main bronchus or abnormal bronchi originated from the trachea are rare2. The most common main bronchus anomalies are the tracheal bronchus and the accessory cardiac bronchus which are of clinical im-portance as they may predispose to infections and, in some cases, to malignancies10. In our study, we evaluated the anomalies of the main bronchus down to the lobar segment.

MDCT has become a very useful tool in the precise investigation of the lung, mainly because of the small slice thickness and the ability of per-forming various post-processing and reformation techniques. By using MDCT, the imaging of the trachea and bronchus is very sufficient down to the subsegmental level2. Reforma-tion techniques include MPR, MinIP, MIP and volume rendering15. VB is a 3D CT post-processing techniques that produces high-resolution endo-bronchial views of the tracheobron-chial tree. This technique simulates the conventional bronchoscopy and is a valuable tool in clinical practice. Consequently, MDCT imaging is an accurate method in the 3D detec-tion of the normal anatomy of the

using MDCT and bronchoscopy show-ing cases of congenital tracheobron-chial anomalies3,4,9–13 and two imaging studies that evaluated the congenital tracheobronchial anomalies in rela-tively small series of patients using

MDCT2,14. In our study, we evaluate the incidence and the demonstration of congenital tracheobronchial anatomi-cal variation of the main bronchus by MDCT and CT bronchoscopy in a large series of 872 patients.

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pre-eparterial. The displaced type was more frequent and it was found in five cases, while the supernumer-ary type was found in three cases. In the literature, the displaced type is referred as more frequent24. In our study, in three cases, the right pre-eparterial bronchi were arising from the junction between the trachea and carina, while in the rest of the cases they were arising from the right main bronchus.

Embryologically, the tracheal bronchus is believed to be created by a failure of regression of the tracheal buds in utero. Normally, tracheal buds regress and when they remain, tra-cheal diverticuli or tracheal bronchi are developed. Another theory sup-ports the disruption of normal em-bryogenesis as the cause of tracheal bronchus rather than the incomplete regression of the tracheal buds6.

The presence of tracheal bron-chus may cause some complications such as atelectasis or pneumothorax in cases of obstructing its entrance or entering into it during intuba-tion19,25–27. Also, there has been a re-ported case of carcinoma originated from tracheal bronchus19,27–29.

bronchus encompasses a wide mor-phological spectrum of variants. Sometimes it arises from the main bronchus and it supplies the upper lobe2,12. It may be an aberrant or a displaced bronchus, and it depends on the anatomical right upper lobe bronchi. The tracheal bronchus is displaced in cases where the right up-per bronchus bifurcates, but it is de-fined as aberrant when the right up-per bronchus trifurcates23. Its length ranges between 0.6 and 2.0 cm24 and its diameter varies from 0.5 to 1.0 cm24. Tracheal bronchus may be ‘true’ tracheal originated from the trachea, at the right side it may be pre-eparte-rial or posteparterial and at the left side it may be eparterial, pre-hypar-terial or posthyparterial2. A tracheal bronchus originated from the main upper lobe bronchus and proximal to its origin is called pre-eparterial on the right side and eparterial or pre-hyparterial on the left side. A tracheal bronchus originated from the main upper lobe bronchus and distal to its origin is called posteparterial on the right side and posthyparterial on the left side2. In our study, all cases of tracheal bronchus variant were right

tracheobronchial system, and it can be used preoperatively. The operative field can be visualized before surgery, any anatomic variant can be seen and the relation between the bronchus and vessels can be detected12.

In our study, the most common variation was the presence of right pre-eparterial tracheal bronchus (0.9%). Also, variations were more frequent in male and in the right lung. These data are in accordance with the literature1,12,16,17.

Tracheal bronchus Tracheal bronchus was first de-scribed by Sandifort in 1785 as a right upper lobe bronchus originated from the trachea18. Tracheal bronchus is a rare anatomic variation with an inci-dence of 0.1–3%2,6,14,19,20. In our study, it was detected at 0.9%.

The tracheal bronchus is a bron-chus usually originated from the right side of the trachea above the carina and within 2–6 cm from it12,21. Right tracheal bronchus has a prevalence of 0.1–2% and left tracheal bronchus has a prevalence of 0.3–1% accord-ing to bronchographic and broncho-scopic studies1,2,7,14,16,20,22. Tracheal

Figure 4: (a) Coronal MPR shows hypoplastic right upper lobe bronchus (arrow). (b) Volume-rendered (VR) 3D image shows aplasia of the right middle lobe bronchus.

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14. Wu JW, White CS, Meyer CA, Hara-mati LB, Mason AC. Variant bronchial ana tomy: CT appearance and classifi-cation. AJR Am J Roentgenol. 1999 Mar;172(3):741–4.15. Remy J, Remy-Jardin M, Artaud D, Fribourg M. Multiplanar and three-di-mensional reconstruction techniques in CT: impact on chest diseases. Eur Radiol. 1998;8(3):335–51.16. Khurshid I, Anderson LC, Downie GH. Tracheal accessory lobe take-off and quadrifurcation of right upper lobe bronchus: A rare tracheobronchial anomaly. J Bronchology. 2003;10(1): 58–60.17. Varju G, Downie GH. Aberrant air-ways: Trifurcation of the right main bronchus. J Bronchology. 2007;14(1): 54–6.18. Kubik S, Müntener M. Bronchus ab-normalities: tracheal, eparterial, and pre-eparterial bronchi. Fortschritte auf dem Gebiete der Rontgenstrahlen und der Nuklearmedizin. 1971;114(2): 145–63.19. Conacher ID. Implications of a tra-cheal bronchus for adult anaesthetic practice. Br J Anaesth. 2000 Aug;85(2): 317–20.20. McLaughlin FJ, Strieder DJ, Har-ris GB, Vawter GP, Eraklis AJ. Tracheal bronchus: association with respiratory morbidity in childhood. J Pediatr. 1985 May;106(5):751–5.21. Horton KM, Horton MR, Fishman EK. Advanced visualization of airways with 64-MDCT: 3D mapping and virtual bronchoscopy. AJR Am J Roentgenol. 2007 Dec;189(6):1387–96.22. Siegel MJ, Shackelford GD, Francis RS, McAlister WH. Tracheal bronchus. Radiology. 1979 Feb;130(2):353–5.23. Foster-Carter A. Broncho-pulmonary abnormalities. Br J Tuberc Dis Chest. 1946 Oct;40(4):111–24.24. Barat M, Konrad H. Tracheal bron-chus. Am J Otolaryngol. 1987 Mar–Apr; 8(2):118–22.25. Ikeno S, Mitsuhata H, Saito K, Hira-bayashi Y, Akazawa S, Kasuda H, et al. Airway management for patients with a tracheal bronchus. Br J Ana esth. 1996 Apr;76(4):573–5.26. Doolittle AM, Mair EA. Tracheal bron-chus: classification, endoscopic analysis, and airway management. Otolaryngol Head Neck Surg. 2002 Mar;126(3): 240–3.

2. Ghaye B, Szapiro D, Fanchamps JM, Dondelinger RF. Congenital bronchial abnormalities revisited. Radiographics. 2001 Jan-Feb;21(1):105–19.3. Schnabel A, Glutig K, Vogelberg C. Bridging bronchus--a rare cause of re-current wheezy bronchitis. BMC Pediatr. 2012 Jul;12:110.4. Bentala M, Grijm K, van der Zee JH, Kloek JJ. Cardiac bronchus: a rare cause of hemoptysis. Eur J Cardiothorac Surg. 2002 Oct;22(4):643–5.5. Endo S, Saitoh N, Murayama F, Sohara Y, Fuse K. Symptomatic accessory car-diac bronchus. Ann Thorac Surg. 2000 Jan;69(1):262–4.6. Gonlugur U, Efeoglu T, Kaptanoglu M, Akkurt I. Major anatomical variations of the tracheobronchial tree: broncho-scopic observation. Anat Sci Int. 2005 Jun;80(2):111–5.7. Beder S, Kupeli E, Karnak D, Kaya-can O. Tracheobronchial variations in Turkish population. Clin Anat. 2008 Sep;21(6):531–8.8. Abakay A, Tanrikulu AC, Sen HS, Aba-kay O, Aydin A, Carkanat AI, et al. Clini-cal and demographic characteristics of tracheobronchial variations. Lung India. 2013 Jul;28(3):180–3.9. Ghaye B, Kos X, Dondelinger RF. Accessory cardiac bronchus: 3D CT demonstration in nine cases. Eur Radiol. 1999;9(1):45–8.10. Yildiz H, Ugurel S, Soylu K, Tasar M, Somuncu I. Accessory cardiac bron-chus and tracheal bronchus anomalies: CT-bronchoscopy and CT-bronchogra-phy findings. Surg Radiol Anat. 2006 Dec;28(6):646–9.11. Baden W, Schaefer J, Kumpf M, Tzari-bachev N, Pantalitschka T, Koitschev A, et al. Comparison of imaging techn iques in the diagnosis of bridging bronchus. Eur Respir J. 2008 May; 31(5):1125–31.12. Akiba T, Marushima H, Takagi M, Odaka M, Harada J, Kobayashi S, et al. Preoperative evaluation of a tracheal bronchus by three-dimensional 64-row multidetector-row computed tomogra-phy (MDCT) bronchography and angiog-raphy: report of a case. Surg Today. 2008; 38(9):841–3.13. Suzuki M, Matsui O, Takemura A, Kob-ayashi T, Yoneda K, Shibata Y. Four cases of accessory cardiac bronchus inciden-tally detected on multi-detector CT. Eur J Radiol Extra. 2006;57(2):47–50.

Accessory cardiac bronchusAccessory cardiac bronchus is a rare congenital anomaly of the TB, and it was first described by Brock in 194630. It is a short and thin bronchus towards the pericardium originated either from the right main bronchus medial wall or from the intermediate bron-chus opposite to the origin of the right upper lobe bronchus. It usually ends blindly and it terminates to a conical lobule located next to azygoesopha-geal recess. Its incidence is referred to be 0.08%2, and it can be differentiated from a fistula or diverticula because it is lined with bronchial mucosa and normal cartilage wall10. Although it is an asymptomatic congenital anomaly, in some cases, it coexists with recur-rent infections or tumours9.

ConclusionPrecise knowledge of normal tra-cheobronchial anatomy and its variants is very important from a radiological and clinical aspect in pre-operative evaluation and in cases of interventional treatments like intu-bation or endobronchial procedures. Also, main lobe bronchus abnormali-ties are of clinical interest because they may predispose to infections, and possibly, to malignancies. MDCT with reformation techniques and VB are two complementary techniques that facilitate the accurate evalu-ation of the tracheobronchial tree and suspected airway abnormalities and can be used as an alternative to bronchoscopy in certain cases.

Abbreviations list3D, three-dimensional; CT, computed tomography; MDCT, multidetector tomographic; MinIP, minimal inten-sity projection; MIP, maximum in-tensity projection; MPR, multiplanar reconstruction; TBV, Tracheobron-chial tree variation; VB, virtual bronchoscopy; VR, volume-rendered

References1. Saad C, Metha A. Accessory cardiac bronchus. J Bronchol. 2002;9(4):311–2.

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tracheal bronchus. Ann Thorac Surg. 2004 Dec;78(6):2163–5.30. Brock R. The anatomy of the bronchi-al tree. London: Oxford University Press; 1946.

Accessory cardiac bronchus present-ing with haemoptysis. Thorax. 1997 May;52(5):490–1.29. Tamura M, Murata T, Kurumaya H, Ohta Y. Leiomyoma of an accessory

27. Aoun NY, Velez E, Kenney LA, Trayner EE. Tracheal bronchus. Respir Care. 2004 Sep;49(9):1056–8.28. Keane MP, Meaney JF, Kazerooni EA, Whyte RI, Flint A, Martinez FJ.

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Tracheobronchial variations evaluated by multidetector computed tomography and virtual bronchoscopy