AJR 2004; 183:290-292
© American Roentgen Ray Society
Partial Tracheal Duplication: MDCT Bronchoscopic Diagnosis
Musturay Karcaaltincaba1,
Mithat Haliloglu1 and
Saniye Ekinci2
1 Department of Radiology, Hacettepe University School of Medicine, Sihhiye,
Ankara 06100, Turkey.
2 Department of Pediatric Surgery, Hacettepe University School of Medicine,
Sihhiye, Ankara 06100, Turkey.
Received September 29, 2003;
accepted after revision November 17, 2003.
Address correspondence to M. Karcaaltincaba.
Introduction
We report partial duplication of the middle part of the trachea as a cause
of stridor in an infant diagnosed on the basis of MDCT bronchoscopic findings.
To our knowledge, partial duplication of the mid trachea has not been
described in the literature.
Tracheal duplication is a rare congenital anomaly. Other congenital
tracheal anomalies include tracheal web, congenital stenosis, cartilage
anomalies, and anomalous bronchi that are distinct from tracheal duplication
[1–5].
Haben et al. [4] and Sen et al.
[5] reported single cases of
partial distal tracheal and complete tracheal duplication, respectively,
diagnosed at postmortem inspection and on chest CT.
Infantile stridor has many causes, and the most common is tracheomalacia,
which accounts for more than half of the cases
[4–6].
Radiology is playing a key role in the search for causes of stridor
[6]. Recently, CT bronchoscopy
has been used as a noninvasive alternative to conventional bronchoscopy. In
this report, we describe the first case of partial duplication of the mid
trachea diagnosed on MDCT bronchoscopy. We propose a possible embryologic
mechanism of development of this anomaly and illustrate the impact of CT
bronchoscopy in diagnosing tracheal malformations.
Case Report
A 2-month-old boy presented with stridor that started shortly after birth.
He was born to a healthy 22-year-old woman who underwent cesarean delivery
after an uneventful full-term pregnancy. He weighed 2,500 g who underwent and
his Apgar scores were normal at birth. His twin sibling had a tetralogy of
Fallot anomaly. Our patient was referred to a pediatrician for evaluation of
stridor. Findings on a chest radiograph and barium swallow were normal. He was
treated with a course of steroids and bronchodilators but showed no
improvement. He weighed 5,200 g on admission. Physical examination revealed
stridor, mild intercostal retractions, and a right inguinal hernia.
We performed CT bronchoscopy with a 4-MDCT scanner (Siemens Volume Zoom,
Siemens Medical Systems) to search for the cause of stridor. Technical
parameters for CT scanning were pitch, 1.5; gantry rotation time, 0.5 sec;
detector collimation, 4 x 2.5 mm; slice thickness, 3 mm; reconstruction
index, 1.5 mm; kVp, 120; and effective mAs, 30. Scanning duration was 3.5 sec.
Free-breathing images had acceptable diagnostic quality. Review of axial and
3D images (obtained on a Leonardo workstation, Siemens Medical Systems) showed
an accessory airway originating from the right posterolateral aspect of the
midportion of the trachea (Figs.
1A and
1B). Distally, an accessory
hypoplastic airway was noted to reunite with the trachea 2 cm above the
carina, which is consistent with partial duplication. The craniocaudal
dimension of the partially duplicated trachea measured 2.5 cm. The accessory
airway was narrower than the main lumen and appeared stenotic at the
midportion (Figs. 1C and
1D). Main lumen diameter at the
level of the partial duplication was smaller than at the proximal and distal
trachea. On volume-rendered images, the origin of the left bronchus appeared
mildly stenotic, but we could not confirm this finding because it was not
possible to pass a bronchoscope with a 2.5-mm diameter beyond the proximal
part of the duplicated trachea (Figs.
1C and
1D). Therefore, we could not
evaluate the duplicated segment of the trachea and carina. No cardiac or
accessory bronchus was noted. An endoluminal view of the trachea was obtained
by postprocessing and showed bifurcation of the main and accessory trachea
proximally (Fig. 1E) and
distally. Bronchoscopically, the proximal part of the duplicated segment of
the trachea was located 3.5 cm distal to the larynx.
View larger version (139K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1A. —2-month-old boy with partial duplication of mid trachea.
Axial CT scans of thorax obtained at two different levels illustrate proximal
(A) and distal (B) parts of duplicated trachea. Note diameter
difference between main lumen and accessory lumen (arrow).
|
|
View larger version (136K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1B. —2-month-old boy with partial duplication of mid trachea.
Axial CT scans of thorax obtained at two different levels illustrate proximal
(A) and distal (B) parts of duplicated trachea. Note diameter
difference between main lumen and accessory lumen (arrow)
|
|
View larger version (96K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1C. —2-month-old boy with partial duplication of mid trachea.
Volume-rendered images of tracheobronchial tree show anterior (C) and
left posterior oblique (D) projections with and without lung
parenchyma, respectively. Extent and configuration of duplicated mid trachea
are seen better on left posterior oblique image (D). Accessory lumen
(arrows) appears stenotic at mid segment.
|
|
View larger version (125K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1D. —2-month-old boy with partial duplication of mid trachea.
Volume-rendered images of tracheobronchial tree show anterior (C) and
left posterior oblique (D) projections with and without lung
parenchyma, respectively. Extent and configuration of duplicated mid trachea
are seen better on left posterior oblique image (D). Accessory lumen
(arrows) appears stenotic at mid segment.
|
|
View larger version (127K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1E. —2-month-old boy with partial duplication of mid trachea. CT
bronchoscopic image, endoluminal view down trachea, shows proximal aspect of
duplicated trachea. Main lumen (short arrow) and accessory lumen
(long arrow) are clearly visible.
|
|
The inguinal hernia was repaired, and the postoperative course was
uneventful. The patient was not in severe respiratory distress, so no surgical
correction was planned. The patient was discharged from the hospital with a
recommendation for close follow-up, with oxygen and humidifier when
necessary.
Discussion
Duplication of the trachea is rare, and to our knowledge only two cases
have been reported in the literature
[4,
5]. One patient had partial
duplication at the lower aspect of the trachea that was seen as a partial
union of the tracheal rings at postmortem analysis
[4]. The infant died shortly
after birth from coexisting unilateral lung hypoplasia. The second patient had
complete tracheal duplication extending from the thoracic inlet to the carina
that was diagnosed on nonhelical CT. CT bronchoscopic images were not
obtained, and the duplicated trachea was shown only on one image in the case
report [5]. Before the CT
procedure, the patient underwent fiberoptic laryngoscopy. The trachea could
not be visualized because the laryngoscope could not pass beyond the larynx.
The parents of the patient refused further treatment, and the severity of
patient's stridor decreased significantly during 1-year follow-up.
To our knowledge, partial duplication at the midportion of the trachea has
not been previously described. The embryologic basis of this anomaly may be
similar to that of anomalous bronchi. Three major hypotheses have been
formulated to explain anomalous bronchi: the reduction, migration, and
selection theories [1]. A
combination of the migration and selection theories may explain the partially
duplicated tracheal anomaly of our patient. The migration theory postulates
that subsidiary outgrowths have the potential to move or migrate from their
initial foci to new points of origin in the bronchus or trachea
[7]. The selection theory
originated from an observation that budding can be induced in the trachea if
active bronchial mesenchyme is grafted onto the tracheal epithelium
[8]. In our patient, bronchial
mesenchyme might have contacted tracheal epithelium during tracheal
development, and later the distal end of the mesenchyme could have migrated to
the trachea and partially duplicated it.
Partial duplication of the trachea can be easily misdiagnosed as an
accessory bronchus or cardiac bronchus if it is not carefully evaluated. The
endoluminal view is similar to that of the tracheal bronchus, and the distal
part of the partially duplicated trachea can be difficult to visualize on
bronchoscopy, as noted in our patient and in one other reported case.
Therefore, it is possible that similar cases in the past may have been
misdiagnosed as tracheal bronchus on bronchoscopy.
CT bronchoscopy is a simple alternative to bronchoscopy and in some cases
can provide more information than conventional bronchoscopy. Early reports
indicated the usefulness of CT in the diagnosis of tracheal stenosis. Since
the introduction of MDCT, 3D imaging has become a routine clinical practice
facilitating diagnosis of tracheal and laryngeal anomalies. With newer 8-and
16-MDCT systems, CT bronchoscopy of pediatric patients can be performed
without breathing artifacts in as little time as 1 sec. This case shows that
even bronchoscopically unreachable areas of the trachea can be visualized in
pediatric patients.
Management options for this condition include surgical or endoscopic
correction and conservative treatment. Lack of experience caused by the rarity
of this congenital malformation is a significant problem in deciding which
treatment would be better for the patient. If the patient is stable,
conservative treatment currently appears to be the safest alternative. CT
bronchoscopic evaluation enables objective and precise measurements for
presurgical planning. In our patient, axial 3D and endoluminal images showed
the location, configuration, and extent of the accessory hypoplastic lumen in
relation to the main tracheal lumen. The main lumen and the accessory lumen of
the trachea were both narrowed.
In conclusion, tracheal duplication is a rare entity that can cause stridor
in infants. MDCT can facilitate the noninvasive diagnosis of such tracheal
anomalies in pediatric patients.
References
- Ghaye B, Szapiro D, Fanchamps J, Dondelinger RF. Congenital
bronchial abnormalities revisited. RadioGraphics2001; 21:105
-119[Abstract/Free Full Text]
- Miller BJ, Morrison MD. Congenital tracheal web: a case report.
J Otolaryngol1978; 7:218
-222[Medline]
- Landing BH, Wells TR. Tracheobronchial anomalies in children.
Perspect Pediatr Pathol1973; 1:1
-32[Medline]
- Haben CM, Nguyen VH, Russell L, Berry MA, Manoukian JJ. Incomplete
tracheal duplication associated with severe unilateral lung hypoplasia.
J Laryngol Otol2003; 117:215
-218[Medline]
- Sen MK, Mehta C, Chakrabarti S, Suri JC. Tracheal duplication as a
cause of congenital stridor. Indian J Chest Dis Allied
Sci 1999;41:159
-162[Medline]
- Goodman TR, McHugh K. The role of radiology in the evaluation of
stridor. Arch Dis Child1999; 81:456
-459[Free Full Text]
- Harris JH Jr. The clinical significance of the tracheal bronchus.
AJR 1958;79:228
-234
- Alescio T, Cassini A. Induction in vitro of tracheal buds by
pulmonary mesenchyma grafted on tracheal epithelium. J Exp
Zool 1962;150:83
-94[Medline]
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
Top
Introduction
Case Report
