【影像征象】胸膜分裂征 | The split pleura sign
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Appearance
The split pleura sign is seen on contrast material–enhanced chest computed tomographic (CT) images. There is enhancement of the thickened inner visceral and outer parietal pleura, with separation by a collection of pleural fluid (Figure) .
胸膜分裂征见于胸部增强CT。增厚及强化的脏层胸膜及壁层胸膜被胸腔积液分离。
Contrast-enhanced transverse CT scan shows
empyema between thickened parietal (arrowheads)
and visceral (arrow) pleural layers: the split
pleura sign.
增强CT横断面显示增厚的脏层胸膜及壁层胸膜间可见脓胸：胸膜分裂征。
Explanation
Thoracic empyema is defined as purulent content in the pleural cavity. Empyema most commonly occurs in the setting of bacterial pneumonia.
脓胸定义为胸腔积液呈脓性。脓胸最常见于细菌性肺炎。
It typically develops from transformation of a parapneumonic effusion (not infected) into a complicated effusion (features of infection but not purulent) and then into empyema (frank pus).
其由类肺炎性胸腔积液（未感染）进展为复杂性胸腔积液（已感染而不是脓性），后进展为脓胸（明显脓性）。
In parapneumonic effusion, fluid moves in the interpleural space due to increased capillary vascular permeability.
类肺炎性胸腔积液，由于毛细血管渗透性增加，液体进入胸膜腔。
Proinflammatory cytokines facilitate the fluid entry into the pleural cavity and cause hyperemia.
促炎细胞因子进入胸膜腔并导致充血。
With increasing fluid accumulation and bacterial invasion through the damaged endothelium, transudative effusion progresses to empyema .
随着液体积聚和细菌通过损伤内皮入侵，漏出液进展为脓胸。
As empyema progresses, a fibrin peel coats the surfaces of the visceral and parietal pleural layers with ingrowth of capillaries and fibroblasts and subsequent thickening.
随着脓胸进展，纤维蛋白覆盖于脏层胸膜及壁层胸膜表面伴毛细血管及成纤维细胞生长，并逐渐增厚。
This forms the basis of the split pleura sign: thickened visceral and parietal pleural layers separated by empyema . The fibrin peel can organize as early as 7 days after the onset of the disease.
这就形成了胸膜分裂征的基础：增厚的脏层和壁层胸膜被积脓分离。纤维蛋白层在发病后7天即可形成。
Discussion
In one major study, pleural separation (“split pleura”) was seen in 68% (39 of 57) of empyema patients. In another study, patients with empyema showed enhancement of the pleura in 86% (30 of 35) of all cases, predominantly of the parietal pleura. Thickening and enhancement can be seen with exsudative effusions in 61% (36 of 59), but not with transudative effusions (5). Empyema is often accompanied by swelling of the extrapleural subcostal tissue (60%, 21 of 35), and increased attenuation of the extrapleural fat can appear (34%, 12 of 35) .
在一项研究中，胸膜分离见于68％（39/57）脓胸患者。在另一项研究中，86％（30/35）的病例可见胸膜强化，主要为壁层胸膜。61％（36/59）的渗出性积液可见胸膜增厚及强化，而渗出性积液未见。脓胸常伴有胸膜外肋下组织肿胀（60％，21/35），并可见胸膜外脂肪密度增加（34％，12/35）。
Pleural changes similar to those of empyema can be seen with malignant effusions (especially after talc pleurodesis), mesothelioma, and hemothorax and after lobectomy (2,7).
恶性胸腔积液（特别是滑石粉胸膜固定术后），间皮瘤，血胸和肺叶切除术后可见与脓胸相似的胸腔积液改变。
About half of empyemas are caused by Gram-positive bacteria (Staphylococcus aureus, Streptococcus pneumoniae); the remainder are Gram-negative organisms commonly growing together with other Gram-negative organisms or anaerobes.
大约一半的脓胸是由革兰氏阳性菌（金黄色葡萄球菌，肺炎链球菌）引起的；其余是革兰氏阴性菌，通常与其他革兰氏阴性菌或厌氧菌一起生长。
In summary, the split pleura sign refers to thickening and increased contrast enhancement of the visceral and the parietal pleura separated by empyema or an exsudative effusion.
总之，胸膜分裂征是指被脓胸或渗出性积液分离的脏层和壁层胸膜增厚和强化。