Reversible bronchial dilatation in children: comparison of serial high-resolution computer tomography scans of the lungs

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Abstract

Introduction: bronchiectasis is generally considered irreversible in the adult population, largely based on studies employing bronchography in cases with a significant clinical history. It is assumed, that the same is true for children. Few studies have examined the natural history of bronchiectasis in children and diagnostic criteria on high-resolution computer tomography of the lungs are derived from studies on adults. Frequently, bronchiectasis is reported in children in cases where localised bronchial dilatation is present, incorrectly labelling these children with an irreversible life-long condition. Objective: to evaluate changes in appearance of bronchial dilatation, unrelated to cystic fibrosis in children, as assessed by sequential high-resolution computer tomography (HRCT) of the lungs. Methods: the scans of 22 children with a radiological diagnosis of bronchiectasis, seen at Alder Hey Children's Hospital between 1994 and 2000, who had at least two CT scans of the lungs were reviewed by a single radiologist, who was blinded to the original report. Results: following a median scan interval of 21 months (range 2–43), bronchial dilatation resolved completely in six children and there was improvement in appearances in a further eight, with medical treatment alone. Discussion: a radiological diagnosis of bronchiectasis should be considered with caution in children as diagnostic criteria derived from studies in adults have not been validated in children and the condition is generally considered irreversible.

Introduction

Bronchiectasis has been defined as a chronic, localised bronchial dilatation, usually associated with inflammation and is considered to be irreversible [1], [2].

As defined by bronchography (now only very rarely performed) bronchiectasis has been described as cylindrical, varicose or cystic, which correlates with increasing degree of severity [3]. A further term, sometimes used is ‘traction bronchiectasis’ which has been employed to describe cases of reversible bronchiectasis associated with pneumonia and, or collapse as described by Nelson and Fleischner [4], [5]. It is a descriptive term applied with the clinical situation in mind and used inaccurately in reporting HRCT of the lungs.

High-resolution CT (HRCT) with 1.5–3 mm collimation has high sensitivity and specificity compared with bronchography and is now the investigation of choice in suspected bronchiectasis [6], [7]. HRCT findings in bronchiectasis include bronchial dilatation, bronchial wall thickening, lack of tapering and bronchi visible closer than two centimetres to the pleural surface. Generally bronchiectasis is considered to be present when the inner diameter of the bronchus is greater than the accompanying pulmonary artery. This observation remains to some degree subjective.

Bronchial dilatation has been well described in adults with asthma. Lynch et al. [8], using the above definition reported bronchial dilatation (at least in 1 bronchus) in 37 (77%) of 48 adult asthmatic patients and bronchial wall thickening in 44 (92%). Bronchial dilatation was found in 16 (59%) and bronchial wall thickening in 5 (19%) of 27 healthy adult controls. They concluded that a bronchus larger in diameter than the adjacent artery was not enough to make a diagnosis of bronchiectasis in the absence of clinical symptoms.

Transient (reversible) bronchial dilatation has been reported with pneumonia and atelectasis in adults [4], [5], [9], [10], [11], [12] and following foreign body inhalation in children [13]. The definition, description and natural history of bronchial dilatation, especially in its milder and localised form in children, is largely derived from studies in the adult population and, as far as we are aware, there is no published study comparing serial HRCT in children. The progress of this bronchial dilatation in these children is unknown.

Singleton et al. [14] described bronchiectasis in 46 Alaska Native Children but only eight had a CT of the lungs. She found predominance of right lung disease especially involving the right upper lobe.

In this study we report the findings and follow-up of 24 children in whom bronchiectasis was reported on the initial HRCT, and who had at least one repeat scan.

Section snippets

Methods

From a computer generated database we identified all children who had had two or more HRCT of the lungs between January 1994 and August 2000 at Alder Hey Children's Hospital and in whom bronchiectasis was reported on the first scan. All the CT scans were then independently reviewed by a single consultant radiologist. All patients where bronchiectasis was deemed not to be present on the first CT scan on this review, were excluded. The criteria used for a diagnosis of bronchiectasis are shown in

CT scanning

High-resolution CT scans with 1- to 2-mm collimation were used for all children. From 1987 to February 2000 the scanner used was a Siemens DRH with 2 mm collimation. The images reviewed were presented on two window settings: (a) window center, −800 HU; window width, 1000 HU; and (b) window center, −600 HU and window width 3750 HU. All the scans were taken in full inspiration at 10-mm intervals from the diaphragm to the apices with the patient in a supine position. Two slices from the apical,

Results

After excluding all children with a diagnosis of cystic fibrosis, 32 children were identified who had two serial CT scans where the first scan showed changes reported as compatible with bronchiectasis. Ten patients were excluded from the study (one patient with dermatomyositis, one child with graft vs. host disease which led to marked destruction of the lung architecture and eight children who had their first scans culled).

Discussion

With increasing availability of ultrafast HRCT it is likely that the number of CT scans done in children to investigate diseases of the chest will continue to increase. A radiological diagnosis of bronchiectasis may be more common than previously thought and the changes that suggest this diagnosis are often quite subtle, especially with cylindrical bronchiectasis. The term bronchiectasis is often loosely applied in reporting HRCT of the lungs where bronchial dilatation is present, which may

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