Chest
Volume 137, Issue 4, April 2010, Pages 938-951
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Chest Imaging and Pathology for Clinicians: Special Feature
Bronchiolar Disorders: A Clinical-Radiological Diagnostic Algorithm

https://doi.org/10.1378/chest.09-0800Get rights and content

Bronchiolar disorders are generally difficult to diagnose because most patients present with nonspecific respiratory symptoms of variable duration and severity. A detailed clinical history may point toward a specific diagnosis. Pertinent clinical questions include history of smoking, collagen vascular disease, inhalational injury, medication usage, and organ transplant. It is important also to evaluate possible systemic and pulmonary signs of infection, evidence of air trapping, and high-pitched expiratory wheezing, which may suggest small airways involvement. In this context, pulmonary function tests and plain chest radiographs may demonstrate abnormalities; however, they rarely prove sufficiently specific to obviate bronchoscopic or surgical biopsy. Given these limitations, in our experience, high-resolution CT (HRCT) scanning of the chest often proves to be the most important diagnostic tool to guide diagnosis in these difficult cases, because different subtypes of bronchiolar disorders may present with characteristic image findings. Three distinct HRCT patterns in particular are of value in assisting differential diagnosis. A tree-in-bud pattern of well-defined nodules is seen primarily as a result of infectious processes. Ill-defined centrilobular ground-glass nodules point toward respiratory bronchiolitis when localized in upper lobes in smokers or subacute hypersensitivity pneumonitis when more diffuse. Finally, a pattern of mosaic attenuation, especially when seen on expiratory images, is consistent with air-trapping characteristic of bronchiolitis obliterans or constrictive bronchiolitis. Based on an appreciation of the critical role played by HRCT scanning, this article provides clinicians with a practical algorithmic approach to the diagnosis of bronchiolar disorders.

Section snippets

HRCT Scan—Anatomic Correlations: Imaging the Secondary Pulmonary Lobule

Bronchioles are small airways < 2 mm in diameter without cartilage or submucosal glands. This includes terminal bronchioles, whose principal role is to conduct air to the respiratory bronchioles.6 The latter contain alveoli, which are the site of air conduction and gas exchange. Critical to the HRCT scan identification of bronchiolar diseases is detailed familiarity with the cross-sectional appearance of secondary pulmonary lobules. As defined by Miller,7 the secondary pulmonary lobule

Stepwise Approach to Bronchiolar Disorders

The clinical presentation of patients with bronchiolar disorders depends on the cause and varies from insidious onset of cough and shortness of breath to an acute, fulminant illness. A proposed algorithmic approach that takes into consideration the history, physical findings, pulmonary function tests, and imaging studies is outlined in Figure 6.

Conclusions

Bronchiolitis is a nonspecific inflammation of the respiratory bronchioles and peribronchiolar alveolar sacs that has variable causes, clinical manifestations, and evolution. However, suggestive, specific diagnoses are rarely made based on clinical history alone. As both CXR and PFT findings are also frequently nonspecific, a high index of clinical suspicion should be maintained in order to diagnose and/or exclude bronchiolar disease. Given these limitations, in our experience, HRCT scanning

Acknowledgments

Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Other contributions: We thank Ms. Patrice Balistreri for her invaluable secretarial assistance and coordination.

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