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Multiple Tracheal Diverticula Detected by Multidetector-row Computed Tomography

Wakisaka, Masaki MD, PhD*; Sohma, Wataru MD; Abe, Hisanori MD; Kawano, Yuichiro MD; Ninomiya, Shigeo MD; Bandoh, Toshio MD; Arita, Tsuyoshi MD; Kobayashi, Michio MD; Okada, Fumito MD§; Mori, Hiromu MD§

Journal of Bronchology & Interventional Pulmonology: October 2010 - Volume 17 - Issue 4 - p 359-361
doi: 10.1097/LBR.0b013e3181f554f0
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Multiple tracheal diverticula are rare. We report a case of a 62-year-old man who had multiple tracheal diverticula that were detected using multidetector-row computed tomography. Axial computed tomography images showed multiple air collections contiguous to the trachea. The multiple air collections were visible as outpouchings of the parts of the trachea between the cartilages, being located almost symmetrically on both lateral sides of the tracheal wall as seen on coronal multiplanar reconstruction images. Virtual bronchoscopy confirmed the presence of multiple openings in the tracheal wall of the diverticular necks. The alteration of the airway was better seen using volume-rendered reconstruction. Thin-slice multidetector-row computed tomography and advanced imaging techniques may increase the frequency of identification of multiple tracheal diverticula.

Departments of *Radiology

Internal Medicine

Surgery, Arita Gastrointestinal Hospital

§Department of Radiology, Oita University Faculty of Medicine, Oita, Japan

Reprints: Masaki Wakisaka, MD, PhD, Department of Radiology, Arita Gastrointestinal Hospital, 1-2-6 Maki, Oita 870-0924, Japan (e-mail: wakisaka@arita-hp.or.jp).

Received for publication July 5, 2010; accepted August 2, 2010

There is no conflict of interest.

Diverticulosis of the tracheobronchial tree is a rare entity that is usually diagnosed during bronchoscopic examinations. Several studies have described this condition,1–8 but little information has been provided regarding the effectiveness of multidetector-row computed tomography (MDCT) for the detection of diverticulosis. We report a case of a 62-year-old man who had multiple acquired tracheal diverticula that were detected using MDCT.

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CASE REPORT

A 62-year-old man visited our hospital for a routine check-up after eradication of Helicobacter pylori infection as a treatment for gastric mucosa-associated lymphoid tissue lymphoma. Routine blood investigations showed no abnormal findings, and an esophagogastric endoscopic examination showed no abnormality. The patient often presented with cough and sputum production. He had smoked 20 cigarettes a day for more than 40 pack-years. CT of the thorax using a MDCT scanner (Asteion Super 4 Edition; Toshiba Medical Systems, Tochigi, Japan) was performed to evaluate the possibility of the pulmonary ailment on the basis of his respiratory symptoms. The CT images were obtained at the end of inspiration and in a supine position. The slice thickness was 3 mm with reconstruction every 3 mm, followed by a sequential high-resolution scan with 1-mm slice thickness. Multiplanar reconstructions (MPR) in the coronal and sagittal projections, virtual bronchoscopy, and volume rendering were also performed at a remote workstation. Axial CT images showed multiple air collections contiguous to the trachea (Fig. 1). The largest air collection was located adjacent to the right posterior wall of the trachea at the level of the second to third thoracic spine. This air collection was thin-walled and multilobular. Multiple air collections of the anterior and both lateral walls of the trachea were several millimeters in diameter and most of these air collections were sack shaped with wide openings. The multiple air collections seemed to be diverticular outpouchings of the parts of the trachea between the cartilages, being located almost symmetrically on the lateral sides of the tracheal wall as seen on the coronal MPR image (Fig. 2). No cartilaginous densities were present in the wall of the diverticular outpouchings. Virtual bronchoscopy confirmed the presence of many openings in the tracheal wall of the diverticular necks (Fig. 3). Volume-rendered reconstruction showed a clearer alteration of the airway (Fig. 4). The lung fields showed emphysematous change and parenchymal scars were also present. The trachea, the right main bronchus, and the left main bronchus were slightly dilatated, with their widest transverse diameters being 28.5, 16.4, and 15.6 mm, respectively. The patient was clinically diagnosed with multiple acquired tracheal diverticula caused by chronic lung disease. Currently, he is undergoing conservative treatment for alleviating the clinical symptoms such as cough and sputum production.

FIGURE 1.

FIGURE 1.

FIGURE 2.

FIGURE 2.

FIGURE 3.

FIGURE 3.

FIGURE 4.

FIGURE 4.

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DISCUSSION

Tracheal diverticulosis is a rarely encountered benign disease characterized by single or multiple invaginations of the tracheal wall.1 Most of the patients are asymptomatic; however, this condition can act as a reservoir for secretions, leading to chronic infections of the tracheobronchial tree and presenting clinically with chronic cough, dyspnea, stridor, and repeated episodes of tracheobronchitis.2 Therefore, the knowledge of this entity is essential for chest physicians and radiologists.

Tracheal diverticulum is divided into 2 types on the basis of histology and location: congenital and acquired. The congenital type is believed to arise from a defect in the endodermal differentiation during development of the membranous posterior tracheal wall or from a defect in the development of the tracheal cartilage during the sixth week of fetal life.1 It is generally located approximately 4 to 5 cm below the true vocal cords on the right tracheal side. The wall of a congenital diverticulum is similar to the wall of the trachea containing smooth-muscle fibers, cartilage, and respiratory epithelium. The acquired type originates as a result of increased intraluminal pressure, thereby resulting in herniation of the mucous membrane through a weak point in the tracheal wall, as seen in bronchopulmonary disorders accompanied by chronic cough. Acquired diverticulum may arise at any level and is said to be typically wide-mouthed and larger in size than congenital diverticulum.2 The wall of an acquired diverticulum is devoid of mucous glands, smooth muscles, and cartilage.

Our patient had a smoking history of 40 pack-years and chronic bronchopulmonary inflammatory changes were suspected on CT images. The diverticula had wide openings to the trachea and no cartilage was apparent in the diverticular wall, although we do not have any pathological evidence. No definite cause-and-effect relationship was identified between chronic bronchopulmonary disease and tracheal diverticula in this case, but an underlying chronic bronchopulmonary disease may have contributed to the formation of multiple tracheal diverticula. Probably, increased intraluminal pressure may have induced a mucosal and submucosal outward bulge between the tracheal rings, thereby producing the acquired diverticula.

Some cases of multiple tracheal diverticuli have already been described in the literature.3–5 Modrykamien et al3 reported a case of multiple tracheal diverticuli in a patient with cystic fibrosis. The presence of multiple diverticula with marked dilatation of the tracheobronchial tree may indicate the Mounier-Kuhn syndrome, which develops as a result of the absence or atrophy of both smooth muscle and elastic connective tissues in the trachea and the main bronchi. Repeated episodes of coughing allow mucosal herniation through the weakened tracheal and bronchial walls.5 The diagnosis is made when the transverse diameter of the trachea measures greater than 3 cm and that of the right and left main bronchi exceeds 2.4 and 2.3 cm on a chest radiograph, respectively.6 This case does not fulfill this anatomic diagnostic criteria.

MDCT can detect small diverticula with the availability of thin slices and high spatial resolution. The features of the diverticulum, such as the size of the diverticular neck and the presence or absence of cartilaginous ring, can also be evaluated using MDCT. Three-dimensional data can be quickly acquired. MPR and volume-rendering techniques improve the spatial evaluation of lesions. Virtual bronchoscopy is a computer-generated 3-dimenisonal CT postprocessing technique that produces high-resolution images of the tracheobronchial tree and endobronchial views that simulate the findings at conventional bronchoscopy. Virtual bronchoscopy can clearly show the diverticular orifice in the tracheal wall as a well-circumscribed hole. The interest in virtual bronchoscopy is increasing because of the improvements in computer hardware and software and advances in MDCT that allow acquisition of isotropic data.7

Tracheal diverticulum has been reported as a rare condition, and its overall prevalence was reported to be approximately 1% of 867 routine serial autopsies in 1953.9 However, in 702 patients, 26 paratracheal air cysts (3.7%) were detected in the MDCT examinations.8 Thin-slice MDCT and advanced imaging processes are effective techniques to detect a tracheal diverticulum and can detect lesions that may have otherwise been missed on thicker slices. Taken together, thin-slice MDCT and advanced imaging techniques may increase the frequency of identification of multiple tracheal diverticula.

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REFERENCES

1. Soto-Hurtado EJ, Penuela-Ruiz L, Rivera-Sanchez I, et al. Tracheal diverticulum: a review of the literature. Lung. 2006;184:303–307.
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3. Modrykamien A, Abdallah R, Kanne J, et al. Multiple tracheal diverticuli in a cystic fibrosis patient. J Bronchol. 2008;15:194–196.
4. Wolf KM, Mathur PN, Busk M, et al. Multiple acquired tracheal diverticula. J Bronchol. 1996;3:43–46.
5. Sanford MF, Broderick LS. Multidetector computed tomography detection of bronchial diverticula. J Thorac Imaging. 2007;22:265–267.
6. Shin MS, Jackson RM, Ho KJ. Tracheobronchomegaly (Mounier-Kuhn syndrome): CT diagnosis. AJR Am J Roentgenol. 1988;150:777–779.
7. Horton KM, Horton MR, Fishman EK. Advanced visualization of airways with 64-MDCT: 3D mapping and virtual bronchoscopy. AJR Am J Roentgenol. 2007;189:1387–1396.
8. Buterbaugh JE, Erly WK. Paratracheal air cysts: a common finding on routine examinations of the cervical spine and neck that may mimic pneumomediastinum in patients with traumatic injuries. AJNR Am J Neuroradiol. 2008;29:1218–1221.
9. Mackinnon D. Tracheal diverticula. J Pathol Bacteriol. 1953;65:513–517.
Keywords:

multiple tracheal diverticula; multidetector-row computed tomography; multiplanar reconstruction; virtual bronchoscopy; volume rendering

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