腹内疝的CT诊断
Because clinical diagnosis of internal hernias is difficult, imaging studies may play an important role if accurate and reliable CT findings can be obtained. However, CT evaluation of any type of internal hernia is rare in the radiology literature, except for a few reports on paraduodenal and transmesenteric hernias.
由于临床诊断腹内疝很困难，如果能获取准确可靠的CT图像表现，那么它就能起到重要的作用。然而，在放射文献中除了有几篇十二指肠旁疝和肠系膜疝的报道外，各种类型腹内疝的CT评估很少。
The most common internal hernia is strangulating SBO, which occurs after a closed-loop obstruction. CT findings of internal hernias include evidence of SBO. To diagnose the hernial strangulation, many researchers stress the importance of observing the configuration of the obstructed loop, mesenteric changes, and the enhancement patterns of the bowel wall (15–19). In this article, we evaluate two characteristic CT findings: bowel configuration and mesenteric changes. The former consists of a saclike mass or cluster of dilated bowel loops. The latter consists of a mesenteric vascular pedicle that is engorged, stretched, and displaced; in addition, the dilated bowel loops have converging vessels at the entrance of the hernial orifice, thus revealing the impaired venous drainage and continuous influx of the arterial flow (1,3,9,10,15–19).
最常见的腹内疝是发生于闭合性梗阻后的绞窄性SBO，腹内疝的CT表现就包括SBO的存在。为了能诊断疝性绞窄，很多研究者强调要观察梗阻肠管的形态、肠系膜的改变和肠管壁的增强模式。本文中我们对两种特征性的CT表现进行评价：肠管形态和肠系膜改变，前者包括扩张肠管囊性团块或堆积，后者包括肠系膜血管蒂的充盈、伸展和移位。另外，在疝孔入口处的扩张肠管的血管汇聚，这可显示受损的静脉回流和连续的动脉灌注。
腹内疝的部位和相关发生频率
The occurrence of abdominal internal hernias is rare. They are reported in 0.2%–0.9% of autopsies (2) and in 0.5%–4.1% of cases of intestinal obstruction (3,8,20). The locations and relative frequencies of internal hernias are as follows: paraduodenal, 53%; pericecal, 13%; foramen of Winslow, 8%; transmesenteric and transmesocolic, 8%; pelvic and supravesical, 6%; sigmoid mesocolon, 6%; and transomental, 1%–4% (1–3,20,21).
腹内疝比较少见，尸检发现率在0.2%—0.9%，肠梗阻病例中占0.5%—4.1%。腹内疝的部位和相关发生频率如下：十二指肠旁，53%；盲肠旁，13%；Winslow孔，8%；经肠系膜和结肠系膜，8%；盆腔和膀胱上，6%；乙状结肠，6%；网膜，1%—4%。
网膜孔疝
Anatomy
解剖
The lesser sac and the greater peritoneal cavity communicate through the epiploic foramen of Winslow. This potential opening is a 3-cm vertical slit situated beneath the upper part of the right border of the lesser sac, cephalad to the duodenal bulb and deep to the liver (Fig 1, A). This foramen is located anterior to the inferior vena cava and posterior to the hepatoduodenal ligament, including the portal vein, common bile duct, and hepatic artery (1–3,22).
网膜囊和腹膜腔通过网膜孔（Winslow孔）相通，这个潜在的孔为上下径约3cm的纵形裂口，从网膜囊的右上缘开口，位于十二指肠球部的头侧和肝脏的深面（图1，A）。网膜孔的后方是下腔静脉，前方是肝十二指肠韧带，其内包含门静脉、胆总管和肝动脉。
Features
特征
Foramen of Winslow hernias make up 8% of all internal hernias (1–3). The intestinal segment most commonly involved is the small intestine (60%–70%). The terminal ileum, cecum, and ascending colon are involved at a rate of about 25%–30% (1,2). Hernias involving the transverse colon, omentum, and gallbladder are rare, although some have been reported in the literature. Predisposing factors include an enlarged foramen of Winslow and excessively mobile intestinal loops due to a long mesentery or persistence of the ascending mesocolon and an ascending colon that is not fused to the parietal peritoneum (1–4,23–26).
网膜孔疝占腹内疝的8%，疝入的肠道一般是小肠（60%–70%），回肠末端、盲肠和升结肠疝入的概率约25%–30%。疝入横结肠、网膜和胆囊的概率很低，仅偶有文献报道。网膜孔扩大，肠系膜过长或升结肠系膜残存而致的肠襻活动度过大，以及升结肠没有和壁层腹膜融合是易患因素。
Characteristic plain radiographic findings are gas-containing intestinal loops high in the abdomen and medial and posterior to the stomach associated with SBO (Fig 3). The cecum and ascending colon may be absent from their usual locations if they are part of the herniated viscera. Barium-enhanced radiography of the small intestine shows dilatation of bowel loops and usually reveals the obstruction at the right upper abdomen. Narrowing or obstruction at the hepatic flexure may be visualized with barium enema examination if the hernia involves the cecum and ascending colon (23). The following are the characteristic CT appearances: (a) presence of mesentery between the inferior vena cava and main portal vein, (b) an air-fluid collection in the lesser sac with a beak directed toward the foramen of Winslow, (c) absence of the ascending colon in the right gutter, and (d) two or more bowel loops in the high subhepatic spaces (1–3,24–26).
腹部平片的特征是上腹部胃内侧和后方发现与小肠梗阻有关的含气性肠襻（图3）。小肠钡剂增强X线片显示肠襻扩张，且通常在右上腹发现梗阻的部位。如果盲肠和升结肠是疝的内容物，则在正常位置不能找到它们，通过钡剂灌肠可能在结肠肝曲发现狭窄或梗阻部位。CT的特征表现如下：（a）下腔静脉和门静脉主干之间发现肠系膜，（b）网膜囊内见朝网膜孔方向鸟嘴状的液气积聚，（c）右腹外侧区不能找到升结肠，和（d）高位肝下见二段以上肠襻。
Figure 3. Foramen of Winslow hernia in a 45-year-old man with acute epigastric pain of 18 hours duration. (a) Abdominal radiograph shows gas-containing small bowel loops (arrows) in the center of the upper abdomen between the liver and the gastric air bubble. (b) Image obtained with enteroclysis performed through a long intestinal tube shows an SBO at the right hepatic flexure (arrow). (c) Contrast-enhanced CT scan of the upper abdomen shows the cluster of dilated small bowel loops (arrowheads) in the lesser sac. There are stretched and converging mesenteric vessels (arrow) between the portal vein in the hepatoduodenal ligament (H) and the inferior vena cava (I). (d) CT scan obtained at the level of the pancreatic head shows crowded mesenteric vessels from the superior mesenteric vein (arrow) between the ascending portion of the duodenum (D) and the pancreatic head (P). Arrowheads = small bowel loops. At laparotomy performed 31 hours after CT, adhesion between the gastrocolic ligament and the transverse mesocolon was found. Approximately 50 cm of ileum, located 200 cm from the ligament of Treitz, was herniated into the lesser sac. The herniated ileal loops demonstrated only congestive changes without gangrene.
图3. 一个45岁男性网膜孔疝，上腹痛持续18小时：（a）腹部X线片显示中上腹肝与胃泡之间的含气性小肠肠襻（箭头）。（b）通过长的导管灌肠造影法显示肝曲小肠梗阻（箭头）。（c）上腹部CT增强扫描显示网膜囊内扩张的簇状肠襻。下腔静脉（I）和肝十二指肠韧带内的门静脉（H）之间见拉长和会聚的肠系膜血管（箭头）。（d）胰头水平CT扫描显示簇状的肠系膜上静脉（箭头）位于十二指肠（D）升部和胰头（P）之间。三角形箭头示小肠肠襻。剖腹手术31小时后CT扫描，胃结肠韧带和横结肠系膜见粘连。手术证实距十二指肠悬韧带200厘米处，大约50厘米长的回肠疝入网膜囊，肠管仅见充血改变而无坏疽。
