【经验】超声内镜引导下细针穿刺活检技术的操作技巧

华盛顿大学医学院Daniel Mullady 博士

目前有多种针头可以用于超声内镜引导下细针穿刺活检(EUS-FNA)。之所以选择一种针头和一种技术通常是参考一些临床资料，但更多的情况是由医生偏好和产品可用性来决定的。

针头的规格

细针穿刺活检针头包括19 - ，22 - ，和25号（G）三个规格。直观的臆测是，更大的针头将提供更大的诊断率，但是这并不正确。有研究显示，22 - 和25-G号针头之间的诊断准确率没有显著差异。我通常使用标准的22-G针头用于胰腺肿块和上皮下病变，使用25-G针头用于肝脏病变、肾上腺病变、淋巴结肿大以及一些我怀疑胰腺病变会带血或其他困难位置（例如，一些大量钩突位置）。当怀疑有粘性分泌物的较大胰腺粘液性囊性病变时，我选择19-G针头，因为对于这些病人，22-或 25-G针头不能提供任何组织（例如，纤维化病变）；同时还可以用于经历了非诊断性抽的一些患者。但常规使用19-G针头会增加标本和并发症发生率，尤其是出血和胰腺炎的潜在风险。

目前不同公司在针头设计上有所不同，但并没有任何一家产品被证明在诊断率上有优势。

FNA技术

1针芯

针芯是预装到针头内腔的金属线，在对病灶进行穿刺后被抽出。针芯可以防止针头被胃肠上皮细胞污染。然而，从随机试验的数据表明，使用针芯与否并不影响诊断率。因此，在做FNA过程中我不使用针芯，但它有助于获得高质量的标本。

2 抽吸

在对病变部位进行穿刺和移除针芯后（如果使用的话），用带负压Luer-Lok接头的注射器固定住针头并加上吸力，然后带动针头在病灶处来回移动。吸力的大小可以通过增加或减少注射器内的负压来调整。如果有过多的血液，我会减少吸入，并用于随后的通道末端。如果分泌物是很少的，我在通道末端增加吸力。数据表明，与低吸力相比，高吸力条件下进行固体胰腺病变的EUS-FNA可以得到更好的诊断率。但高吸力能增加其他样本的血染，尤其是淋巴结和血管病变。

湿吸力的变化是将针芯在针头进入病灶前去除，同时针用无菌生理盐水冲洗。当针头到达靶病变处后才开始吸。这可以提供温和的吸力由于真空是通过液体而不是空气进行传播。在慢拉技术中，针头进入靶病变处后，在针头来回穿刺过程中针芯慢慢退出，这时通过毛细管作用提供温和的吸力。这有可能实现低创伤性FNA和比标准吸入操作更少流血的样本。

3针头从病变处以扇形来回穿刺的次数

这方面目前没有标准和研究数据。我一般将针头在病变处以扇形穿刺10-15次。通过控制抬钳器重定向针，从而获取靶病变的不同区域的样本。数据表明扇形操作可以帮助改善诊断准确率。在每次穿刺时，我尽力以扇形穿刺病变区域的3-4个不同区域。

4穿刺次数

在没有现场细胞病理学家参加的情况下，我的实践是在实性病变处进行6-7次穿刺和在淋巴结肿大处进行3-4次穿刺，从而最大程度地提高诊断率。而进一步增加穿刺次数反而影响判断。在有现场细胞病理学家辅助的情况下，我一般会保证2次穿刺，如果遇到非诊断部位或者病理学家要求多采集一个细胞组织块样本的情况下，我会增加一次穿刺。

5 FNB与FNA的对比

FNB的概念是吸引人的，因为这将允许进行组织学而不是细胞学评价。传统来讲，通过EUS-FNA可靠地获取核心样品的能力是受限的。但是，最近在针尖的设计修正和对大口径针头灵活性的改进可以带来进一步的突破。已经有证据表明FNB可以在更少穿刺的情况下获得与FNA相似的诊断率，这对没有快速病理学检测的超声内镜具有极大帮助。 但是，当进行EUS-FNA时，细胞学知识足够判断。例外情况包括淋巴瘤，胃肠道间质肿瘤，自身免疫性胰腺炎，和以前的非诊断性活检，这些疾病中要做出明确的诊断，核心活检可能是必须的。

 结语

进行FNA操作时，超声内镜在针的设计和技术方面具有众多选择。了解现有的数据、组织采集的需要（例如细胞学与组织学）和靶病变位点的性质（如预期的肝纤维化或血性损伤）对选择针和调整FNA技术从而确保始终如一的高诊断率非常重要。

Introduction

Endosonographers currently have many choices regarding needles for endoscopic ultrasound–guided fine-needle aspiration (EUS–FNA). The choice of one needle and one technique over another is guided by some clinical data but most often is dictated by physician preference and product availability.  

Needle size

FNA needles are available in 19-, 22-, and 25-gauge (G) sizes. An intuitive assumption is that a larger needle size will provide a greater diagnostic yield, but this is not always true. Studies have revealed no significant difference in diagnostic accuracy between 22- and 25-G needles.1–4 I typically use a standard 22-G needle for pancreas masses and subepithelial lesions, and I use a 25-G needle for liver lesions, adrenal lesions, and lymph nodes, or if I suspect that a pancreas lesion will be bloody or in a difficult location (eg, some uncinate process masses). I reserve 19-G needles for larger pancreatic mucinous cystic lesions in which I suspect a viscous aspirate, when a 22- or 25-G needle does not provide any tissue (eg, fibrotic lesions), and for some patients who have previously undergone non-diagnostic aspirates. Routine use of 19-G needles may potentially increase the bloodiness of specimens and rate of complications, particularly bleeding and pancreatitis.

Differences in needle-tip design

There are some needle-tip design differences among companies, none of which have been demonstrated to provide an advantage in diagnostic yield.

FNA technique

Use of a stylet

A stylet is a metal wire that comes preloaded into the lumen of the needle and is withdrawn after the lesion is punctured. The stylet may prevent contamination of the needle by gastrointestinal epithelium. However, data from randomized trials suggest that the use of a stylet does not affect diagnostic yield.5,6 As such, I do not use a stylet during FNA, but it can be useful for expressing a specimen onto a slide.

Suction

Following puncture of the target lesion and removal of a stylet (if one is used), a negative-pressure Luer-Lok syringe is affixed to the needle and suction is applied as the needle is moved back and forth through the lesion. The degree of suction can be adjusted by increasing or decreasing the negative pressure within the syringe. If there is too much blood, I decrease the suction and use it at the end of the subsequent pass. If the aspirate is scant, I increase the suction for the subsequent pass. Data suggest that performing EUS–FNA of solid pancreatic lesions with high suction provides a better diagnostic yield compared with low suction,7 but high suction can increase the bloodiness of other specimens, particularly from lymph nodes and vascular lesions.

Wet suction is a variation in which the stylet is removed prior to needle insertion and the needle is flushed with sterile saline. Once the needle is in the target lesion, suction is applied. This may provide gentler suction because the vacuum is transmitted through liquid rather than air. In the slow-pull technique, the needle is advanced into the target lesion, and the stylet is slowly withdrawn as the needle is moved back and forth, providing gentle suction though capillary action. This possibly results in a less traumatic FNA and a less bloody specimen compared with standard suction.8

 Number of times the needle is passed back and forth through the lesion and fanning

This is not standardized and there are no data. I will typically pass the needle back and forth approximately 10 to 15 times, fanning within the lesion. Fanning is redirecting the needle using the elevator and up/down dial on the scope in order to sample different areas of the target lesion. Data suggest that fanning provides improved diagnostic yield.9 I try to fan in three to four different locations in the lesion on every pass.

Number of passes

In the absence of an on-site cytopathologist, my practice is to perform six to seven passes for solid lesions and three to four passes for lymph nodes, which maximizes diagnostic yield. More passes than this has diminishing returns.10 In the presence of an on-site cytopathologist, I will typically obtain two passes and perform additional passes only if these are non-diagnostic or if the pathologist requests additional samples for cell block.

FNA vs fine-needle core biopsy (FNB)

The concept of FNB is appealing because it would allow for histologic rather than cytologic evaluation. Traditionally, the ability to reliably obtain a core specimen via EUS–FNA has been limited. However, recent modifications in needle-tip design and improvements in flexibility of larger-caliber needles are promising. There is evidence that FNB obtains similar diagnostic yield to FNA but with fewer passes, which may be useful for endosonographers who do not have rapid on-site cytopathology.11 However, cytology is often sufficient when performing EUS–FNA. Exceptions include lymphoma, gastrointestinal stromal tumors, autoimmune pancreatitis, and previously non-diagnostic FNA in which a core biopsy might be necessary to provide a definitive diagnosis.

 Summary

Many choices in needle design and technique are available to endosonographers for performing FNA. Understanding available data, tissue-acquisition needs (ie, cytology vs histology), and the nature of the target lesion (ie, anticipated fibrotic or bloody lesion) are important in choosing a needle and tailoring FNA technique to ensure consistently high diagnostic yield.

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