大小网膜的正常解剖及异常影像学课件

Greater and Lesser Omenta: Normal Anatomy and Pathologic Processes,大网膜和小网膜的正常解剖及异常影像表现,Eunhye Yoo, MD, Joo Hee Kim, MD, Myeong-Jin Kim, MD,大网膜和小网膜是个非常复杂的解剖区域。正因为如此，网膜病变从积液到弥漫性网膜浸润，CT表现表现多种多样，同时又无特征性。网膜不仅是限制病变扩散的屏障，同时又是病变传播的途径。 累及网膜的病变：感染、炎症、 肿瘤、 外伤 和坏死。 高分辨率螺旋CT扫描同时行MPR 能很好显示网膜的解剖结构和病变状况。充分认识网膜的影像解剖和病变的各种CT表现及一些特征性征象，对诊断和治疗具有非常必需的。,CT 扫描参数和重建技术 采用 16-section CT scanner，平扫和 增强: 0.5-second rotation time, 0.75-mm collimation, 3-mm section thickness, 35-cm field of view, 3-mm reconstruction thickness, 12-mm feed per rotation, 120 kV, and 140 mA。 常规采用3-mm section thickness 断面图像 。后处理工作站进行 sagittal、 coronal, or oblique 多平面重建。,正常解剖 大网膜主要由脂肪组织和一些细小扭曲的胃网膜血管 gastroepiploic vessels构成。 CT表现为位于前腹壁下，胃、横结肠和小肠前之间的一组不同宽度的 脂肪组织, 。在大网膜和邻近的软组织结构间的腹水衬托下，大网膜显示为一单纯的脂肪层., 一旦网膜出现异常的软组织病变，则显示 为模糊状、条索状、结节状影和肿块. 小网膜由肝胃韧带和肝十二指肠韧带组成，它将胃小弯、远侧十二指肠和肝脏 连接起来，覆盖小网膜的前方。肝胃韧带内含 胃左血管和胃左组淋巴结。肝十二指肠韧带，为小网膜侧方厚层，内含门静脉、肝动脉、肝外胆管和,肝门组淋巴结。 正常情况下小网膜囊是闭合的, 只有它的边如胃后壁、胰腺体部才可以在CT上显示。,Greater and Lesser Omenta: Normal Anatomy and Pathologic Processes1,Drawing of the anatomy of the greater and lesser omenta ： The greater omentum (GO) is composed of a double layer of peritoneum that extends from the greater curvature of the stomach (S) inferiorly. Its descending and ascending portions usually fuse to form a four-layer vascular fatty apron; the resulting space is contiguous with the lesser sac (LS). The lesser omentum (LO) connects the lesser curvature of the stomach and proximal duodenum with the liver (L) and contains blood vessels, nerves, and lymph nodes. The lesser sac is empty and collapsed so that only parts of its boundaries, such as the posterior gastric wall and pancreatic body, are observed on axial CT scans. Ao = aorta, C = colon, K = kidney, P = pancreas, Sp = spleen, 1 = falciform ligament, 2 = gastrohepatic ligament, 3 = gastrosplenic ligament.,Greater and Lesser Omenta: Normal Anatomy and Pathologic Processes1,Ao = aorta, C = colon, K = kidney, P = pancreas, Sp = spleen, 1 = falciform ligament, 2 = gastrohepatic ligament, 3 = gastrosplenic ligament.,Axial,Greater and Lesser Omenta: Normal Anatomy and Pathologic Processes1,coronal,Ao = aorta, C = colon, K = kidney, P = pancreas, Sp = spleen, 1 = falciform ligament, 2 = gastrohepatic ligament, 3 = gastrosplenic ligament.,Greater and Lesser Omenta: Normal Anatomy and Pathologic Processes1,Ao = aorta, C = colon, K = kidney, P = pancreas, Sp = spleen, 1 = falciform ligament, 2 = gastrohepatic ligament, 3 = gastrosplenic ligament.,大网膜病变 。 大网膜病变的CT征象： (a)多灶性，边界不清的浸润性病灶： 癌性腹膜炎、结核性腹膜炎、恶性间皮瘤、腹膜假性粘液瘤、 淋巴瘤和肝硬化源性门脉高压。 (b) 囊实性肿块： 原发性和继发性肿瘤和感染病变; (c) 其它各类病变： 网膜梗塞坏死、 异物肉芽肿、血肿和 疝。,A、多灶性，边界不清，浸润性病灶 Multifocal, Ill-defined, Infiltrating Lesions a. 肝硬化源性网膜水肿 b. 播散性腹膜肿瘤 c. 感染性腹膜炎 癌性腹膜炎、恶性间皮瘤和淋巴瘤等播散性腹膜肿瘤和结核性腹膜炎的鉴别是十分困难的，因为它们临床症状不典型，影像征象重叠（ overlapping imaging features）。 网膜异常的CT征象如fatty stranding 、 结节状浸润（ nodular infiltration） 、肿块和网膜饼（ omental caking）在各种病变中均可显示，并没有明显差异。,Greater and Lesser Omenta: Normal Anatomy and Pathologic Processes,肝硬化源性网膜水肿（infiltrative edema from liver cirrhosis） 合并门脉高压的肝硬化是弥漫性网膜性病变最常见的原因之一，肝硬化患者在CT上常常可以显示网膜、肠系膜和后腹膜水肿。网膜水肿的CT 表现多种多样： 从轻度的薄雾状到边界清楚的肿块范围内的一系列改变，和其它网膜病变的表现并无异样。,b. 弥漫性腹膜肿瘤（diffuse peritoneal tumor） 肿瘤腹膜种植转移 原发灶大多来自胃、胰腺、结肠、子宫和膀胱，血运性转移多来自恶性黑色素瘤（ malignant melanoma）、乳腺癌和肺癌。 癌性腹膜炎的征象 ： 腹水、腹膜增厚、种植性结节和网膜浸润 （omental infiltration）但是这些征象并非癌性腹膜炎所特有，也可以存在于其它种类的病变累犯种植于腹膜：间皮瘤 mesothelioma、结核 和 淋巴瘤病。 因此，我们在临床工作中首先应该 努力寻找消化道和泌尿道的原发肿瘤。大家知道，网膜饼是癌性腹膜炎的一个常见征象，但不是其特征性征象。网膜增厚轮廓呈不规则状改变才是癌性腹膜炎较为有用的征象。,.,Peritoneal carcinomatosis from the stomach in a 22-year-old man with epigastric pain。CT scans show large amounts of ascites, diffuse nodular omental infiltration (omental cake) (arrows), and abnormal gastric wall thickening 。,Peritoneal carcinomatosis in a 30-year-old woman with malignant melanoma. CT scan shows hematogenous dissemination of malignant nodules in the peritoneal space including the omentum (arrows), retroperitoneal spaces, and the subcutaneous fat layer of the abdomen.,c. 感染性腹膜炎 infectious peritonitis 结核性腹膜炎起因肺结核的血性播散和肠系膜淋巴结结核的破溃，支持结核性腹膜炎 CT 表现: 1、腹膜稍增厚，边缘光滑。smooth peritoneum with minimal thickening 2、肠系膜显著强化，合并直径5mm的多发大结节。pronounced enhancement, mesenteric involvement with macronodules (5 mm in diameter) 3、细薄的网膜线。a thin omental line (fibrous wall covering the infiltrated omentum) 4、肿大淋巴结，中心为低密度(caseous necrosis), 5、多发钙化。 纤维粘连型结核性腹膜炎虽然比较少见，其特征为包裹腹腔积液呈多房状改变。巨大网膜肿块和肠袢分离和固定。,Tuberculous peritonitis in a 38-year-old woman with abdominal distention for 1 week. CT scan shows a large amount of ascites with even peritoneal thickening (arrowhead) and diffuse omental infiltration (arrow) without associated lymphadenopathy. The initial impression was carcinomatosis. When the primary malignancy is unclear, the differential diagnosis should include tuberculous peritonitis, particularly in endemic areas. The final diagnosis was tuberculous peritonitis.,D、恶性腹膜间皮瘤Malignant peritoneal mesothelioma 腹膜恶性间皮瘤很少见，占人体所有间质瘤的 12%33%。恶性腹膜间皮瘤CT表现多种多样。常见：腹水、不规则或结节状腹膜增厚、肠系膜星芒状改变（ a “stellate” pattern of the mesentery）、 肠壁增厚和网膜受累，其包括：脂肪间隙细条状、污斑状、散在分布网膜结节和网膜饼（ finely infiltrated fat with a “smudged” appearance to discrete omental nodules or omental caking）。 有时也表现为上腹部一个较大的但大小尚可测量的肿块，同时合并少量腹水和腹膜上一些散在分布结节。s a large quantifiable mass in the upper abdomen with minimal ascites and discrete nodules scattered over the peritoneum.,Malignant peritoneal mesothelioma in a 47-year-old man with dyspnea for 1 month. CT scan shows a diffuse, platelike mass in the greater omentum (arrows), massive ascites, and peritoneal thickening. Malignant mesothelioma was confirmed with pleural biopsy and cytologic analysis of peritoneal fluid.,E、腹膜假性粘液瘤Pseudomyxoma peritonei 腹膜假性粘液瘤为大量粘液性腹水的渐进性积聚而成。 这些粘液是由原发于阑尾、卵巢、胰腺、胃、乙状结肠、直肠和子宫的良性和恶性粘液性肿瘤破溃所形成。腹膜假性粘液瘤 CT表现：腹膜腔、网膜和系模内低密度、多房性液体积聚。内脏表面，尤其为肝脏，CT显示扇形、拱形改变是区别粘液性抑浆液性腹水一个特征性征象。粘液内常可见到曲状和点状钙化。,Pseudomyxoma peritonei in a 47-year-old man with abdominal discomfort. CT scans show multiple low-attenuation nodules and masses in the omentum and peritoneal cavity. Curvilinear or punctate calcifications of the seeding nodules; scalloping of the liver, spleen, and stomach; and small bowel adhesions from mesenteric infiltration are noted. seudomyxoma peritonei was proved with peritoneoscopic biopsy.,腹膜淋巴瘤病 Peritoneal lymphomatosis 腹膜淋巴瘤不像其它腹膜恶性肿瘤，可以不需经手术而治愈的病变。 CT上由于它与癌性腹膜炎、结核性腹膜炎 的表现非常相似，诊断非常困难。但是如果腹水没有包裹和多房改变，同时合并多发肿大淋巴结，需提示淋巴瘤病的可能。一旦肠系膜和后腹膜肿大显示，其常为均一密度或中间低密度而周边环状强化。网膜改变主要为网膜污状和饼状改变。散在结节状改变比较少见。,Peritoneal lymphomatosis in a 71-year-old man with abdominal distention for 15 days. CT scan shows ascites in the pelvic cavity and innumerable seeding nodules in the peritoneal cavity and omentum (white arrow). Multiple enlarged lymph nodes with conglomeration (black arrows) are seen in the retroperitoneal spaces. Endoscopic gastric biopsy showed B-cell lymphoma.,B、囊实性肿块样病变 Solid or Cystic Mass-forming Lesions a、累及大网膜的继发性肿瘤 继发性大网膜肿瘤发病率远高于原发性肿瘤。许多肿瘤均可经直接播散、腹膜种植和血行转移而累及网膜。 肿瘤大多起源于卵巢、胃、胰腺和结肠。,Secondary neoplasm of the greater omentum in an 80-year-old woman with dyspepsia. Coronal CT scan shows a large lobulated mass (arrows) in the left upper quadrant of the abdomen. The mass represents an exophytic tumor from the greater curvature of the stomach, a finding suggestive of an exophytic gastric carcinoma.,Metastatic peritoneal tumor in a 73-year-old woman with a palpable abdominal mass for 2 months. CT scan shows a large, lobulated, heterogeneous mass in the midabdomen, inferolateral to the stomach. Thickened peritoneum (arrow) adjacent to the mass is suggestive of a malignant lesion. Metastatic carcinoma was confirmed at surgical excision. The patient had a history of ovarian carcinoma.,b、原发性网膜肿瘤Primary neoplasms of the omentum 原发性网膜肿瘤比较少见，包括：间皮瘤（mesotheliomas）、血管外皮细胞瘤（hemangiopericytomas）、间质瘤、 平滑肌瘤、 脂肪瘤、神经纤维瘤病、纤维瘤、平滑肌肉瘤、脂肪肉瘤和纤维肉瘤. 原发网膜肿瘤影像征象没有特异性。良性肿瘤常常为孤立、边界清楚。恶性肿瘤常边界不清，易浸润周围脏器。良性和恶性肿瘤表现复杂、可为囊性和囊实性。部分囊性病变可累及大网膜，包括囊性淋巴管瘤、常重复囊肿（ enteric duplication cyst）肠囊肿（ enteric cyst） 、间皮囊肿（mesothelial cyst）和非胰腺性假性囊肿。腹部淋巴管瘤的特征性表现： 一单房或多房充液肿块，壁薄，偶而有间隔（a uni- or multiloculated fluid-filled mass with a thin wall and occasionally with septa ）。,Abdominal lymphangioma in a 38-year-old woman with a gastric ulcer, which was an incidental finding at CT. CT scans show a lobulated cystic mass in the greater omentum inferior to the gastric antrum. The mass is most likely a cystic lymphangioma.,c、少见的感染性病变 Unusual infections 少见的感染性病变如放射菌病（ actinomycosis ）或肺吸虫病（ paragonimiasis）可以表现为网膜中的实性或囊性肿块。 放射菌病广泛分布于全世界城乡地区，常累及面颈、胸腔 和腹盆区域。它 喜渗透和侵犯正常解剖屏障倾向， 表现为实性肿块伴内 局部密度减低或为肿块大部囊性变伴壁不规则增厚且不均质强化solid mass with focal areas of decreased attenuation or a mostly cystic mass with irregularly thickened, heterogeneously enhanced walls on CT scans。其它炎性肿块尤其结核，有相似表现，可能导致误诊。 肺吸虫病主要位于肺，但其它器官也可发病。 常见的CT表现：多发致密钙化小结节散布于腹膜腔。 multiple, densely calcified, small nodules scattered in the peritoneal cavity . 虽然吸虫病累及网膜临床意义不大，但了解这种影像表现有助于早期诊断，避免不必要的手术治疗。,Abdominal paragonimiasis in a 49-year-old man with hepatic lesions incidentally found during laparoscopic cholecystectomy. (a) CT scan shows multilocular cystic lesions in the right lobe of the liver. (b) CT scan shows multifocal ill-defined cystic lesions and several nodules (arrow) in the omentum on the right side of the abdomen. These appearances are suggestive of multilobulate parasitic abscesses in the liver with peritoneal seeding of parasitic granulomas. Biopsy of the liver and omentum demonstrated paragonimiasis.,d、混合性病变 Miscellaneous Lesions 网膜扭转、节段性坏死少见，临床上为急腹症表现。原发性网膜扭转原因不明。继发性网膜扭转多见。原因：疝、局限性炎症、早期的腹部手术或肿瘤。由于多发生于右侧网膜，临床症状不典型，有时和阑尾炎和胆囊炎相似。 CT findings ：网膜轻微、灶性、模糊状软组织样病变广泛、肿块样病变。脂肪组织 围绕系膜内血管结构扭转或许是网膜扭转的一个征象。大网膜刀刺伤多见. blunt injury少见。. 网膜血管结构损伤也会引起网膜坏死。,Omental infarction in a 47-year-old man with abdominal pain. CT scans show localized fatty infiltration and congestion with a secondary mass (arrow) in the right lower aspect of the anterior abdomen. This appearance most likely indicates an omental infarction。,Foreign-body granuloma in a 39-year-old woman with a palpable mass for 10 years and abdominal pain for 1 week. Unenhanced CT scan shows a large, well-circumscribed mass with dense calcification in the anterior midabdomen, an appearance suggestive of a foreign-body granuloma or organizing hematoma. After injection of contrast material, the mass showed no enhancement. A foreign-body granuloma with surgical gauze 沙布瘤 was found at surgical excision. The patient had a history of cesarean section 10 years earlier。,Ventral hernia in a 66-year-old woman with a palpable mass in the abdomen. Sagittal CT scan shows herniation of omental fat through a defect (arrow) in the anterior abdominal wall. Focal ill-defined lesions with increased attenuation (arrowheads) in the omental fat adjacent to the abdominal wall defect are suggestive of omental fat infarction secondary to vascular compromise.,腹后外侧疝 Bochdalek hernias Bochdalek hernias (腹后外侧疝) 是最常见的先天性膈疝。常见于左侧。 疝入的器官：网膜脂肪组织、小肠、胃、脾和肝左叶。由于肺发育不全，这些病人出生时即有症状。也有一些个例报道患者直至成人也无症状。. Morgagni hernias (胸骨后疝) 也是一种少见的膈疝，常见于右边。稍后位于胸骨剑突后。 Morgagni hernias 常见于儿童，无症状而无意中发现。 Traumatic diaphragmatic hernias 常因于外伤，车祸伤和坠落伤、刀刺伤和医源伤。 左侧膈肌多见。医源疝常见于胸腹联合手术，如食道癌进行的胃食道手术. 疝口固定疝入器官引起的并发症，常可在CT扫描和多平面重建中显示。,Morgagni hernia in a 70-year-old woman with an abnormality at chest radiography. Axial (a), coronal (b), and sagittal (c) CT scans show focal upward displacement of the transverse colon and omental fat (arrows in b and c) in the right anterior cardiophrenic area, an appearance suggestive of a Morgagni hernia。,Abnormalities Involving the Lesser Omentum and Lesser Sac 涉及小网膜和小网膜囊病变的CT表现： 漏出和渗出腹水、炎性渗出液、 bile或血液积聚 囊实性肿块（包括炎症和肿瘤） 腹内疝。 internal hernias.,（a）Fluid Collection in the Lesser Sac 正常情况下，小网膜囊是空的，闭合的。CT上只能见到其所组成边界的器官。 小网膜囊积液： 腹水、分泌液、 bile, and blood. 小网膜囊最常见的积液为肝肾功能不全患者的漏出性腹水。但是只有在小网膜囊内见到积液是不常见的。腹膜腔内的大量腹水通过网膜孔而并不是直接通过网膜进去的。肝胃手术后单纯的小网膜囊积液应该首先考虑术后积液，或者为胰腺炎、胆囊炎和器官穿孔并发的病理性积液。,Fluid collection in the lesser sac in a 36-year-old man 2 days after subtotal gastrectomy with gastrojejunostomy for stomach cancer. CT scans show a collection of meglumine diatrizoate in the lesser sac (black arrow). This finding was suggestive of leakage (white arrow in b) from the anastomosis of the gastrojejunostomy; such leakage was visualized during an upper gastrointestinal study with meglumine diatrizoate 2 days later。,Inflammatory infiltrate in the lesser sac in a 68-year-old man with a history of heavy alcohol use who had epigastric pain for 2 days. CT scans show infiltration of peripancreatic fat (a) and spread of an inflammatory exudate to the lesser sac (arrow in b) and retroperitoneal space, findings suggestive of acute pancreatitis.,Lesser sac hematoma 1 day after abdominal blunt trauma in a 40-year-old man with acute abdominal pain. Contrast-enhanced CT scan shows a large acute hematoma in the lesser sac between the stomach and pancreas. Emergent laparotomy with hematoma evacuation and “bleeder“ ligation was performed,（b）Discrete Mass in the Lesser Omentum or Lesser Sac 网膜囊上隐窝的占位性病灶：pancreatic pseudocysts