【影像征象】树芽征 | The tree-in-bud sign

zskyteacher 2018-11-27

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【Radiology-Signs in imaging】

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Appearance

The tree-in-bud sign is the constellation of small centrilobular nodules and concomitant branching opacities, which mimics the branching pattern of a budding tree. The nodules and connecting branches are peripheral but spare the subpleural lung.
树芽征是小叶中心小结节和伴随的分枝状影，形似树芽。结节和分支状影是外周性的，但不累及胸膜下肺。

Explanation

The appearance of the tree-in-bud sign is closely linked to the anatomy of the secondary pulmonary lobule.
树芽征表现与次级肺小叶密切相关。

The diseased small airway often becomes visible as fluid replaces gas in the small airway and inflammation thickens the bronchiolar walls.This results in a V- or Y-shaped branching pattern, which together with centrilobular nodularity forms the tree-in-bud sign.

小气道病变由于液体代替小气道内气体和支气管管壁炎性增厚而可识别。V形或Y形的分枝状影和小叶中心结节一起形成树芽征。

Discussion

Although the tree-in-bud signhas primarily been used as a descriptive term for endobronchial spread of Mycobacterium tuberculosis, it is now recognized as a common pattern that can be seen in many pulmonary diseases and disorders including infection (most common), aspiration, and rarely neoplastic conditions (such as low-grade adenocarcinoma).
尽管树芽征最初用于描述结核分枝杆菌的支气管内播散，现为多种肺疾病的一种常见征象，包括感染（最常见）、吸入、少见肿瘤性病变（低级别腺癌）。

In Mycobacterium tuberculosis, the tree-in-bud sign results from impaction of caseous material in the bronchioles of the secondary pulmonary lobule.
在结核分枝杆菌中，树芽征是由于干酪质物质在次级肺小叶细支气管中的嵌塞所致。

Identification of the tree-in-bud sign along with other imaging findings such as bronchial wall thickening or narrowing, bronchiectasis, consolidation, cavitation, and/or necrotic lymphadenopathy, as well as an appropriate exposure history, supports the diagnosis.

树芽征合并其它影像学表现，如支气管壁增厚或变窄、支气管扩张、实变、空洞和/或淋巴结坏死及合适的暴露史可支持诊断。

This is in contradistinction to non-tuberculous mycobacterial pneumonia in which centrilobular or tree-in-bud nodularity and bronchiectasis with volume loss (usually most severe in the right middle lobe and lingula) predominate.
这与非结核分枝杆菌性肺炎形成对比，其中以小叶中心或树芽状结节和支气管扩张为主，伴肺容积减小（通常在右中叶和舌叶最严重）。

Non-tuberculous mycobacterial pneumonia usually occurs in middle-aged to elderly women who often have low body mass index and kyphoscoliosis.
非结核分枝杆菌肺炎通常发生在中年至老年妇女，她们往往体重指数低和脊柱后凸。

The tree-in-bud sign may also be present in other types of pneumonia (such as Staphylococcus aureus and Haemophilus influenzae) as pus or inflammatory secretions impact the distal small airways.
树芽征也可见于其他类型肺炎（如金黄色葡萄球菌和流感嗜血杆菌），由于脓液或炎性分泌物影响远端小气道。

In patients with aspiration, a gravitational and lower lung predominance of the tree-in-bud pattern is often observed.
在吸入性患者中，树芽征常以重力区和下肺为主。

A rare but underrecognized cause of the tree-in-bud sign is distant metastatic disease (e.g. from breast, hepatic, ovarian, prostatic, and renal primaries). The appearance is due to carcinomatous endarteritis—inflammatory intimal hyperplasia of the small pulmonary arteries secondary to filling with tumor cells.
罕见但未被充分认识病因是远处转移性疾病（例如来自乳腺、肝脏、卵巢、前列腺和肾脏原发灶）。表现是由于内膜炎-小肺动脉继发于肿瘤细胞填充的炎性内膜增生。