Chest
Volume 139, Issue 6, June 2011, Pages 1445-1450
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Original Research
Bronchiectasis
Bronchoarterial Ratio on High-Resolution CT Scan of the Chest in Children Without Pulmonary Pathology: Need to Redefine Bronchial Dilatation

https://doi.org/10.1378/chest.10-1763Get rights and content

Background

The radiologic definition of airway dilatation and bronchiectasis in children has substantial limitations. Bronchoarterial (BA) ratio is a commonly used criterion to define airway dilatation despite the lack of normative pediatric data. The objective of our study was to determine the range of normal bronchial to accompanying arterial diameter ratio on high-resolution CT scan of the chest in children and compare it with the available adult data.

Methods

Children undergoing multidetector CT scan of the chest for nonpulmonary conditions at a single center were prospectively identified. High-resolution reconstruction was performed on those included and both airway lumen and vessel diameters were measured in the upper and lower lobes of both lungs. Mean BA ratio was calculated for each included child, and its correlation with age was assessed.

Results

Forty-one children were included; the mean (SD) BA ratio was 0.626 (0.068) (range, 0.437-0.739). This ratio was lower than comparable adult data (combined mean [SD], 0.676 [0.12]; P = .01). No correlation was found with age in our cohort (r = −0.21, P = .19). There was no difference in the ratio based on laterality or lobe.

Conclusions

In the pediatric age group, the airway is significantly smaller than the adjoining vessel. Using the radiologic criteria of BA ratio > 1 to define bronchial dilatation would underestimate the presence and extent of bronchiectasis, leading to delayed and missed diagnosis. This highlights the need to redefine the criteria for bronchial dilatation in children.

Section snippets

Materials and Methods

All helical MDCT scans of the chest undertaken at our tertiary pediatric center were prospectively screened from October 2009 to May 2010. Exclusion criteria were history of chronic cough (cough duration > 4 weeks); known cardiopulmonary condition, such as cystic fibrosis, bronchial asthma, previous pneumonia, chronic suppurative lung disease, congenital  /acquired cardiac disorders, and so forth; presence of any (previous or current) pulmonary metastasis; previous/current chest radiotherapy or

Results

Of the 340 scans screened over the 8-month period, 41 (17 boys, 24 girls) met the inclusion criteria. The median (range) age at CT scan was 99 (5-214) months. IV contrast was administered in all CT scans with seven scans done under general anesthesia. Staging and progress of lymphoma was the most common indication for the CT chest scan. Details of indications for the included CT chest scans are given in e-Table 1.

Discussion

This prospective HRCT scan chest analysis of 41 children without pulmonary pathology shows that the mean BA ratio for the whole cohort was 0.626 (95% CI, 0.604-0.648). We did not find any correlation between BA ratio and age.

Normative data on airway and vessel dimensions in children are scarce. BA ratio is important because it is one of the most objective and commonly used criteria to define radiologic bronchial dilatation and bronchiectasis. Despite the evidence to the contrary,13, 21, 24 the

Acknowledgments

Author contributions: Dr Kapur: contributed to the study concept and design, radiologic measurements, analysis and interpretation of the data, drafting of the article, and statistical analysis.

Dr Masel: contributed to the study concept and design, radiologic measurements, and drafting of the article.

Ms Watson: contributed to HRCT scan reconstruction from raw data on included children and drafting of the article.

Dr Masters: contributed to the study concept and design and drafting of the article.

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      Each lung was assessed separately using maximal magnification, such that the axial image of the lung filled the entire area of the viewing screen. Obliquity was assessed by calculating the following ratio for both bronchus and artery – long-axis diameter:short-axis diameter, with ratios >1.5 excluded as described by Kapur et al. [10]. The middle lobe and lingula were excluded as the typical orientation of bronchi on axial images, as well as artifact caused by cardiac motion, make these regions unsuitable for inclusion in this protocol [13].

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    Funding/Support: This study was funded by the Australian National Health and Medical Research Council [525216] to Dr Chang and ANZ Trustees PhD Scholarship to Dr Kapur.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).

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