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 Sonography in Identification of Abdominal Wall Lesions Presenting as Palpable Masses

Abstract
Objective. Abdominal wall lesions often present as palpable masses. The purpose of this presentation is to provide an overview of the sonographic appearances of different abdominal wall lesions. Methods. Patients were scanned with high-frequency (5- to 12-MHz) linear transducers. Extended or panoramic views were recorded often to show the lesion in perspective to adjacent structures in the abdominal wall. Results. The different layers of the abdominal wall could be clearly shown on high-frequency sonography, and the abdominal wall abnormalities were recognized in all the patients. Conclusions. Hernias are the most common abdominal wall lesions. Herniated bowel loops have variable appearances depending on their air-fluid content and degree of obstruction. Localized fluid collections in the abdominal wall (seromas, liquefying hematomas, and abscesses) can be well visualized. More infrequently, tumors or vascular lesions can be identified in the abdominal wall.

摘要

目的：腹壁病变常表现为可触及的肿物。本文的目的是概括各种腹壁病变的超声表现。方法：病人经高频线阵探头（5－12MHz）扫描，运用扩展或全景观察方式显示病变及其邻近结构。结果：高频超声能清楚显示腹壁不同的层面，能识别所有病人中的腹壁异常。结论 疝是最常见的腹壁病变，疝出肠管的表现因其气液含量和梗阻程度的不同而存在差异。腹壁内局限性积液（血清肿、血肿液化和脓肿）能清晰显像，不很常见的腹壁肿瘤或血管病变也能予以鉴别。

Key Words: abdominal sonography • abdominal wall • hernia

关键词：腹部超声 腹壁 疝

Introduction
Abdominal wall lesions often mimic intra-abdominal conditions and frequently present as palpable masses. This is more common with patients who have a thick abdominal wall with a large layer of fat. Pathologic processes that may involve the abdominal wall occasionally raise diagnostic challenges because of the low specificity of physical findings. The most common situation when a sonographic examination of the abdominal wall is needed is when there is a doubt about a palpable abdominal mass to decide whether it is in the abdominal wall or inside the abdominal cavity. Sometimes a clinically suspected intra-abdominal mass proves to be in the wall, and sometimes an abdominal wall lesion is seen as an incidental finding on abdominal sonography performed for some other reason. Often patients with chronic abdominal pain need an examination of the abdominal wall, especially when a positive Carnett sign suggests the cause of pain to be in the abdominal wall.

序论

腹壁病变常与腹内情况相似，常表现为可触及的肿物，而在具有大量脂肪层、腹壁较厚的病人更为常见。累及腹壁的病变有时会增加诊断的难度，因为其体格检查的特异性较低。对可疑的腹部可触及肿物要确定是位于腹壁还是位于腹腔内时，常常需要超声检查。有时临床怀疑为腹内肿物而证实是位于腹壁内，也有时在因其他原因行腹部超声检查时可偶尔发现腹壁的病变。慢性腹痛的病人，尤其是Carnett征阳性提示是由腹壁原因导致的疼痛时常常需要腹壁检查。   

Materials and Methods
Patients were scanned with a Voluson 730 Expert system (GE Healthcare, Milwaukee, WI), an AU4 Idea system (Esaote SpA, Genoa, Italy), and an HDI 5000 system (Philips Medical Systems, Bothell, WA) with high-frequency (5- to 12-MHz) linear transducers. Extended or panoramic views were recorded often to show the lesion in perspective to adjacent structures in the abdominal wall. There was no need for any abdominal preparation. Any abdominal wounds were cleaned and, if possible, covered with a thin, sterile, plastic adhesive membrane, or, more simply, the probe was covered with a sterile cover or glove. Patient’s ages ranged from neonate to 68 years.

资料和方法

病人经Voluson 730 Expert、AU4 Idea 、HDI 5000高频（5－12MHz）线阵探头扫描，用扩大或全景切面显示病变以便区别腹壁邻近结构，并不需要任何腹部准备。每处腹部伤口都予以清洁，可能的话在探头上覆盖一层薄的无菌塑料膜，或者更为简单的将探头覆盖一无菌覆盖物或手套。病人年龄从新生儿到68岁不等。

Anatomy
The abdominal wall is a laminated structure. The different layers are skin, superficial fascia, subcutaneous fat, muscle layer, the transversalis fascia, and a layer of extraperitoneal fat (Figure 1 ). The anterior muscle layer is composed of paired midline rectus muscles and anterolaterally situated internal and external oblique and transverse abdominis muscles. The rectus abdominis muscles are attached superiorly to the anterior arcs of 5 to 7 ribs and inferiorly to the pubic crest. They are enclosed within the anterior and posterior layers of the rectus sheath, which is a continuation of the aponeurosis of the internal oblique, external oblique, and transverse abdominis muscles. The posterior rectus sheath ends at the arcuate line, midway between the umbilicus and symphysis pubis. In midline, the anterior and posterior layers of the rectus sheath fuse to separate the 2 recti and form the linea alba.

解剖

腹壁是一层状结构，分别为皮肤层、浅筋膜层、皮下脂肪层、肌肉层、腹横筋膜和腹膜外脂肪层（图1）。前面肌肉层由中线处成对的腹直肌、前外侧的腹内外斜肌和腹横肌组成，腹直肌向上附着于5－7肋弓前面，向下止于耻骨嵴，并包绕在腹直肌鞘的前层和后层内。腹直肌鞘为一连续的腹内斜肌、腹外斜肌和腹横肌的腱膜，其后层止于弓状线，中间位于脐和耻骨联合之间。在正中线，腹直肌鞘前层和后层融合形成白线，将两侧腹直肌分开。

Figure 1. A, Anterior abdominal wall on a transverse scan. RA indicates rectus abdominis; EO, external oblique; IO, internal oblique; and TA, transverse abdominis. The arrow points to the aponeurosis of lateral muscles. B, Layers of the rectus sheath on a transverse scan of the abdominal wall. Arrows point to the anterior rectus sheath, peritoneum, and fascia transversalis.
图1，A ，前腹壁横断扫描。RA，腹直肌；EO，腹外斜肌；IO，腹内斜肌；TA，腹部横切。箭头指向侧肌腱膜。B，腹壁横断扫描显示腹直肌鞘层。箭头指向腹直肌鞘前层、腹膜和腹横筋膜。

 

The skin is echogenic. The subcutaneous fat layer is variable in thickness and is usually hypoechoic. The muscles reveal medium-level echoes. A typical lamellar pattern of the muscle fibers usually can be recognized.
皮肤表现不同回声，皮下脂肪层厚度存在差异，常表现为低回声，而肌肉表现为等回声。典型的片状肌纤维通常能够显示。

Fluid Collections
积液

Localized fluid collections in the abdominal wall are seromas, abscesses, or liquefying hematomas.
腹壁局部积液可以是血清肿、脓肿或溶解的血肿。

Non infected seromas after surgery are usually anechoic collections. Fluid collections complicated by infection or hemorrhage appear more complex, with variable degrees of internal echoes, layering, and septa (Figure 2 ).
术后未感染的血清肿常为无回声的积液，并发于感染或出血的积液其表现比较复杂，内部回声程度、分层和分隔常不同（图2）。

Figure 2. Abdominal wall seroma after surgery.
图2，术后腹壁血肿