Learning objectives
Radiologists frequently encounter bronchiolitis or distal airway pathology on images. This article aims to simplify the concept of bronchiolitis and facilitate the formulation of a concise and accurate differential diagnosis. We will describe the entities encompassed within the distal airway pathology, distinguishing between cellular and constrictive bronchiolitis. Likewise, we will review the characteristic clinical data typically associated with each entity.
Background
Bronchiolitis or small airways disease refers to injury affecting the bronchioles and alveolar ducts, leading to inflammation or fibrosis. Bronchioles are small airways with a diameter of 2 mm or less located at the center of the secondary pulmonary lobule (SPL). Normally, these small airways are imperceptible on imaging but become visible when abnormal (fig.1).[Fig 1]SPL is the functional unit of the lung and is key to comprehending chest terminology and physiology of multiple diseases. A nuanced knowledge of the distribution of its internal and...
Findings and procedure details
Even though there is no consensus classification system for small airways disease, one of the most accepted and used at pathologic examinations divides these conditions into two broad categories: cellular bronchiolitis (CB) and constrictive or fibrotic bronchiolitis (FB).Histologically, CB is characterized by inflammatory cells as the predominant feature, in contrast to FB, which refers to bronchiolar narrowing due to adventitial and submucosal fibrosis.Various forms of CB are well acknowledged, encompassing infectious bronchiolitis (IB), respiratory bronchiolitis (RB), aspiration bronchiolitis (AB), follicular bronchiolitis (FLB), hypersensitivity pneumonitis (HP),...
Conclusion
Bronchiolitis, encompassing a spectrum of airway pathologies with significant clinical impact and varying treatments, poses a challenge for radiologists due to the frequent overlap of imaging findings. These pathologies are categorized into cellular bronchiolitis, characterized by centrilobular nodules with or without a 'tree-in-bud' pattern, and fibrotic bronchiolitis, associated with mosaic attenuation pattern. Within cellular bronchiolitis, numerous entities exhibit distinct imaging findings and associated clinical data that aid in diagnosis. Fibrotic bronchiolitis represents a pattern often associated with a clear clinical background, such as lung transplantation...
Personal information and conflict of interest
J. López Martín:
Nothing to disclose
M. M. Merideño García:
Nothing to disclose
A. Enriquez Puga:
Nothing to disclose
A. A. Gil:
Nothing to disclose
E. Ponte:
Nothing to disclose
E. F. Berríos:
Nothing to disclose
M. S. Paez Alvarez:
Nothing to disclose
P. Garcés Marín:
Nothing to disclose
A. D. Onuta:
Nothing to disclose
References
Abbott GF, Rosado-de-Christenson ML, Rossi SE, Suster S. Imaging of small airways disease. J Thorac Imaging. 2009 Nov;24(4):285-98. doi: 10.1097/RTI.0b013e3181c1ab83. PMID: 19935225.
Berniker AV, Henry TS. Imaging of Small Airways Diseases. Radiol Clin North Am. 2016 Nov;54(6):1165-1181. doi: 10.1016/j.rcl.2016.05.009. Epub 2016 Aug 11. PMID: 27719982.
Department of Radiology, Hospital Universitario de Toledo.
Kang EY, Woo OH, Shin BK, Yong HS, Oh YW, Kim HK. Bronchiolitis: classification, computed tomographic and histopathologic features, and radiologic approach. J Comput Assist Tomogr. 2009 Jan-Feb;33(1):32-41. doi: 10.1097/RCT.0b013e3181635e50. PMID: 19188782.
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