Thursday 25 October 2007
Definition: Bronchial atresia is a distinct pathological entity that accounts for recurrent pneumonia or respiratory distress in childhood, requiring surgical treatment.
Congenital bronchial atresia (CBA) usually presents incidentally in asymptomatic young male adults but is rarely diagnosed in children. Congenital bronchial atresia presents differently in children than in young adults.
Pathologic findings include a cystic, blindly terminating, mucus-filled bronchocele without connection to the main bronchial tree, but with normal subsequent generations of bronchi.
Bronchial atresia is characterized by a mucocele (or bronchocele) resulting from a mucus-filled, blind-terminating sub-segmental, segmental or lobar bronchus, at or near its origin, and hyperinflation of the isolated lung parenchyma. More than 100 cases have been reported in the English literature since 1953, when the abnormality was first described.
The lung parenchyma that is to be supplied by the affected bronchus is usually emphysematous, non-compressible, non-inflamed, and minimally anthracotic because it does not communicate directly with the environment.
The air that exists in the affected parenchyma is the result of the collateral ventilation through the pores of Kohn, the bronchoalveolar channels of Lambert or via interbronchiolar channels.
The process of hyperinflation may occur shortly after birth with the start of respiration, since the proposed pathways for collateral ventilation favour the movement of air into the obstructed segment by a check-valve type mechanism.
At the root of the involved tissue a mucus filled cystic structure (the mucocele) with finger-like projections represents the atretic bronchus, which is isolated from the proximal bronchial tree and is dilated by the accumulated mucus. The bronchial pattern distally to the mucocele is usually normal.
Bronchial atresia is usually diagnosed in the second or third decade of life. It seems that the disorder has a male predominance, with an estimated prevalence of 1.2 cases per 100,000 males.
The insidious course of the disorder explains its late detection in some patients. About half to two thirds of the reported patients had been asymptomatic before diagnosis. Recurrent pneumonias, dyspnea, cough or haemoptysis have been reported less frequently.
On chest radiograph the typical findings of a mucocele is that of a nodule or a mass like shadow close to the hilum, with well-defined margins, which usually forms the apex of a roughly triangular zone of hyperlucency of the lung parenchyma (due to oligemia and hyperinflation).
However, the synchronous appearance of both the mucocele, as described above, and the lung hyperlucency, on the same radiograph, is not always seen (69%).
A mucocele with an air-fluid level is considered as a variance of the radiographic images of congenital bronchial atresia.
Some authors believe that this finding is encountered in case of an infection, and this is consistent with the presented patient who had a history of pneumonias. Although the exact mechanism of this finding remains obscure (given the overall rarity and benign course of this disorder), it has been proposed that with infection at the area the impacted mucous may liquefy producing the radiological sign of an air-fluid level.
In fact the described "cavitary lesion" was not a cavity that was produced after a destructive pneumonia, but a distended (by the mucous) airway, which after the liquefaction of the impacted mucous, as a result of an infection, took the appearance of a "cavity" with an air-fluid level in it.
CT remains the procedure of choice for the diagnosis and study of congenital bronchial atresia. Chest CT, especially using high resolution technique, can display exquisitely the characteristic features of the mucocele and is more sensitive, than the conventional chest radiograph, for the demonstration of the oligemia, the reduced size of the pulmonary vessels and the hyperinflation of the lung parenchyma.
Bronchoscopy may identify a blind-ending bronchus, but it may be normal as well.
In clinical practice however, any absence of a segmental or sub-segmental bronchus that is found by chance during bronchoscopy, in the absence of the characteristic radiographic features, may be considered as a normal anatomic variance of the bronchial tree rather than a bronchial atresia.
From this point of view, in the majority of cases, congenital bronchial atresia remains a radiological diagnosis. The CT findings (mucocele with hyperaeration of the adjacent lung parenchyma) are considered pathognomonic by most authors. However, some publications suggest that similar findings could be found in serious disorders as well, such as lung cancer or bronchial adenoma. The role of bronchoscopy is to exclude these disorders and demonstrate the patency of the central bronchi, especially in doubtful cases.
Can occur at any level from lobar to subsegmental bronchus
Clinically presents in older children
- chest infection
mucocele at the level of obstruction
- possible calcified mucocele (21447937)
obliterated bronchial lumen
- lumen obliteration by loose fibrous tissue with spindle cells
thickening of the peribronchial interstitium
dilatation of the distal parenchyma with accumulation of mucus and macrophages
round or lobulated perihilar, solid or cystic mass
bronchocele (14966358, 8963626)
proximal blind-ending bronchus
Increasingly evident that some form of bronchial atresia is present in association with sequestration, CPAM and lobar emphysema.
extralobar sequestration (16953677)
intralobar sequestration (16953677)
congenital cystic adenomatoid malformation (CCAM) or congenital pulmonary airway malformation (CPAM) (16953677)
lobar emphysema (16953677)
pulmonary bronchial cysts
lobar bronchial atresia
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Riedlinger WF, Vargas SO, Jennings RW, Estroff JA, Barnewolt CE, Lillehei CW, Wilson JM, Colin AA, Reid LM, Kozakewich HP. Bronchial atresia is common to extralobar sequestration, intralobar sequestration, congenital cystic adenomatoid malformation, and lobar emphysema. Pediatr Dev Pathol. 2006 Sep-Oct;9(5):361-73. PMID: 16953677
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Matsushima H, Takayanagi N, Satoh M, Kurashima K, Kanauchi T, Hoshi T, Kanazawa M. Congenital bronchial atresia: radiologic findings in nine patients. J Comput Assist Tomogr. 2002;26:860–864.