Author: Wang Xiaojie
Source: Chinese Journal of Gastrointestinal Surgery, 2024, 27(9)
Summary
The ligaments associated with colon cancer surgery mainly include gastrocolic ligaments, diaphragmatic and splenic ligaments. In the era of traditional open surgery, surgeons often treated ligaments with large clamps. In recent years, with the rise and development of membrane anatomy research, colorectal surgeons, with the assistance of high-definition laparoscopic vision, have gradually traced the origin of various traditional anatomical structures, and the surgery based on the concept of membrane anatomy has become more refined.
Based on the author's anatomical observations, this article analyzes the membrane anatomical nature of the ligaments associated with colon cancer surgery, and discusses its surgical and oncological significance. Gastrocolic ligaments have different membrane anatomys in the omentum sac and non-omental sac areas. In the omental sac area, in addition to the paracolic pathway, the subarchal path is an alternative method of entering the omental sac from the gastrocolic ligament. In the non-omentum sac area, the omentum covering the surface of the mesangial transverse mesocolonic space is incised, and the bridge into the space is made. The probability of omental arch lymph node metastasis in transverse colon cancer and colon liver asperoid carcinoma is very low, and screening high-risk patients with lymph node metastasis in this group for dissection still has survival benefit. The splenic and colic ligament is formed by the fusion of the splenic hilar structure of the dorsal mesangium of the stomach (including the mesangium of the pancreas) and the mesangium of the colon splenic flexure in close proximity to each other, with a natural bloodless separation plane in between, in which the separation of the left omentum artery branches encountered in the traditional separation path can be avoided. There is no evidence to support the need for resection of the dorsal mesangial tissue in the hilar area of the splenic hilum or lymph node dissection of the gastroretic arch for splenic flexure colon cancer.
As an ancient anatomical structure, ligament is a white band-like connective tissue with dual characteristics of toughness and elasticity, the main components are collagen fibers and elastic fibers, and its main function is to fix the position of certain organs such as liver, spleen, kidney, colon, etc. The ligaments associated with colon cancer surgery mainly include gastrocolic ligaments, diaphragmatic and splenic ligaments. In the era of traditional open surgery, surgeons often treated ligaments with large clamps. In recent years, with the rise and development of membrane anatomy research, colorectal surgeons, with the assistance of high-definition laparoscopic vision, have gradually traced the origin of various traditional anatomical structures, and the surgery based on the concept of membrane anatomy has become more refined. In addition, sorting out the embryonic development process of fascia is helpful to understand the scope of organ envelope and the law of cancer metastasis. Based on the results of the author's anatomical research, this paper intends to distinguish the membrane anatomical nature of the ligaments associated with colon cancer surgery from the perspective of membrane anatomy, and discuss its surgical and oncological significance.
1. Gastrocolic ligaments
(1) Principle of embryonic development of gastrocolic ligament (omentum sac area)
During the embryonic stage, the intestinal tube rotates around the superior mesenteric artery, and during the rotation, the dorsal mesangium of the stomach expands outward into the pouch-like shape to form the omentum. Among them, the second layer of the omentum continues with the third layer to form the medial wall of the omentum sac. The 4th layer of the omentum gradually covers the dorsal lobe of the transverse mesocolon and fuses to form a fused fascia, which together forms part of the transverse mesocolic root, as shown in Figure 1 in green. Because the second and third layers of the omentum in adults are usually more and more fused, see Figure 1 in gray; The greater curvature of the stomach is connected to the transverse colon to form the gastrocolic ligament, as shown in Figure 1 with a blue dotted box. It can be seen that the gastrocolic ligament essentially belongs to the dorsal mesangial structure of the stomach and does not belong to the mesocolonic envelope.
(2) Membrane anatomy of the gastrocolic ligament
1. At the level of the omentum sac (transverse colon and splenic flexure of the colon): the 4th layer of the omentum gradually covers the dorsal lobe of the transverse mesocolon and fuses to form a fused fascia, which together as part of the transverse mesocolic root and runs behind the tail of the pancreatic body, see Figure 2. During the free process of splenic flexure colon, the gastrocolic ligament structure formed by the fusion of the 3rd and 4th layers of the omentum can often enter the omentum sac by incising the gastrocolic ligament structure next to the colon, see the red arrows in Figure 2 and Figure 3. It is important to note that the 3rd and 4th layers of the omentum in this area are often incompletely fused, and sometimes the two layers of fascia need to be cut one at a time until the posterior wall of the stomach is visible, and entry into the omentum sac can be determined. In addition, the omentum often encloses the transverse colon, resulting in severe adhesion in this area, which makes it difficult to enter the omental sac directly, and there is a risk of damage to the transverse colon and intestinal tube, as shown in Figure 4. At this time, the omental sac can be entered by incising the gastrocolic ligament composed of the first and second layers of the omentum under the omentum arch, where it is the thinnest and often translucent, see the blue arrows in Figure 2 and Figure 5; It is also an ideal alternative route to the omental sac.
2. At the level of the non-omental sac (transverse colon and colon hepatic flexure, subpyloric area): different from the omental sac level, the dorsal mesangium of the stomach on the flexure side of the liver extends caudally to the caudal side, forming the right part of the omentum, covering the dorsal lobe of the transverse mesocolon, and partially fused. At the same time, the root of the omentum covers the opening of the transverse mesocolonic space of the gastric mesoconium, so that the mesocolic and gastric mesomesis of the hepatic flexure form a special "丅" topology. Among them, "one" is the omentum, and "丨" is the mesoconic space of the gastric mesocolon [ 1 ]. See Figure 6. Subpyloric lymph nodes (i.e., group 206 lymph nodes) are not intracolic structures in nature, but rather gastroduodenal. If the omental arch lymph nodes need to be dissected during colon cancer surgery, supraarch separation is performed along the greater curvature of the stomach, as shown in Figure 6. The right gastroomental artery innervated the anterior and posterior branches of the stomach were cut off sequentially, and finally the right gastric omental artery was ligated at the root to communicate with the caudal free side to complete the omental arch lymph node dissection, as shown in Figure 6 (the blue range is the gastro omental arch lymph node dissection). If omental arch lymph nodes do not need to be dissected, subarch dissection of the greater curvature of the stomach is performed, as shown in Figure 7. During the separation from the medial to the flexure of the liver, the omentum (the "one" in the "丅" type) is incised, which is actually the mesangial transverse mesocolonic bridge, see Figure 8. It can enter the meso-gastric transverse mesocolonic space ("丨" in the "丅" type), and the surface of the mesogastric and transverse mesocolon is smooth, which can avoid bleeding, see Figure 9.
(3) Oncological significance of gastrocolic ligaments
There are gastroomental blood vessels in the gastrocolic ligament, and there is still controversy about whether omental arch lymph node dissection is required for transverse colon cancer, including colonic liver asperoid carcinoma. From the perspective of embryonic development, the gastrocolic ligament is essentially part of the dorsal mesangium of the stomach and does not belong to the mesocolonic envelope. Notably, the fusion of the omentum and the transverse colon and its dorsal mesangial lobes forms fine lymphatic and vascular communication between the two, which can serve as a potential "extramesangial" metastatic pathway for transverse colon cancer [2]. Previous literature has reported that the metastasis rate of omental arch lymph nodes in transverse colon cancer (including colon liver asperoid carcinoma) is 0.7%~22.0% [3]. Previous single-center retrospective studies have suggested that the metastasis rate of omental arch lymph nodes in transverse colon cancer and colon liver aspermatic carcinoma is about 4% [4]. In view of the low probability of omentum lymph node metastasis and the risk of postoperative gastric paralysis can be increased by omentum lymph node dissection, the authors suggest individualized dissection for patients at high risk of omental arch lymph node metastasis [5]. Some scholars recommend omental arch lymph node dissection for T3~T4 stage proximal transverse colon cancer [6]. Based on a single-center retrospective study, the authors found that T1~2 transverse colon cancer does not metastasize to the omental arch lymph nodes, and can not be dissected; However, the inability of the lens to pass through the tumor lesion (endoscopic obstruction) during preoperative colonoscopy, preoperative carcinoembryonic antigen higher than 17 μg/L, M1 stage, lymphangiovascular tumor thrombus, and signet ring cell carcinoma are risk factors for omental arch lymph node metastasis in transverse colon cancer and colon liver asperoid carcinoma, which are helpful for screening high-risk groups for colon cancer ochoroid arch lymph node metastasis [6]. In addition, further research is needed to determine whether endoscopic or laparoscopic injection of nanocarbon or indocyanine green tracing into tumors is helpful in the detection of omental arch-positive lymph nodes.
It is worth noting that there is a difference between the retinal arch lymph node sub-station and the gastric cancer lymph node sub-station in colon cancer, and the first gastric major curved artery is often used to distinguish group 4 and group 6 lymph nodes in gastric cancer, because the first gastric greater curved artery can be accurately anchored in the postoperative specimen of gastric cancer. However, the omental arch lymph node dissection of colon cancer generally follows the "omental arch" principle, that is, the omental arch lymph nodes within 10 cm of the vertical range from the tumor are removed [7].
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Membrane anatomy of ligament structures associated with colon cancer surgery
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