[Intraoperative anatomical observation of mesentery morphology of colonic splenic flexure].

Objective: At present, surgeons do not know enough about the mesenteric morphology of the colonic splenic flexure, resulting in many problems in the complete mesenteric resection of cancer around the splenic flexure. In this study, the morphology of the mesentery during the mobilization of the colonic splenic flexure was continuously observed in vivo, and from the embryological point of view, the unique mesenteric morphology of the colonic splenic flexure was reconstructed in three dimensions to help surgeons further understand the mesangial structure of the region. Methods: A total of 9 patients with left colon cancer who underwent laparoscopic radical resection with splenic flexure mobilization by the same group of surgeons in Union Hospital of Fujian Medical University from January 2018 to June 2019 were enrolled. The splenic flexure was mobilized using a "three-way approach" strategy based on a middle-lateral approach. During the process of splenic flexure mobilization, the morphology of the transverse mesocolon and descending mesocolon were observed and reconstructed from the embryological point of view. The lower margin of the pancreas was set as the axis, and 4 pictures for each patient (section 1-section 4) were taken during middle-lateral mobilization. Results: The median operation time of the splenic flexure mobilization procedure was 31 (12-55) minutes, and the median bleeding volume was 5 (2-30) ml. One patient suffered from lower splenic vessel injury during the operation and the bleeding was stopped successfully after hemostasis with an ultrasound scalpel. The transverse mesocolon root was observed in all 9 (100%) patients, locating under pancreas, whose inner side was more obvious and tough, and the structure gradually disappeared in the tail of the pancreatic body, replaced by smooth inter-transitional mesocolon and dorsal lobes of the descending colon. The mesenteric morphology of the splenic flexure was reconstructed by intraoperative observation. The transverse mesocolon was continuous with a fan-shaped descending mesocolon. During the embryonic stage, the medial part (section 1-section 2) of the transverse mesocolon and the descending mesocolon were pulled and folded by the superior mesenteric artery (SMA). Then, the transverse mesocolon root was formed by compression of the pancreas on the folding area of the transverse mesocolon and the descending mesocolon. The lateral side of the transverse mesocolon root (section 3-section 4) was distant from the mechanical traction of the SMA, and the corresponding folding area was not compressed by the tail of the pancreas. The posterior mesangial lobe of the transverse mesocolon and the descending mesocolon were continuous with each other, forming a smooth lobe. This smooth lobe laid flat on the corresponding membrane bed composed of the tail of pancreas, Gerota's fascia and inferior pole of the spleen. Conclusions: From an embryological point of view, this study reconstructs the mesenteric morphology of the splenic flexure and proposes a transverse mesocolon root structure that can be observed consistently intraopertively. Cutting the transverse mesocolon root at the level of Gerota's fascia can ensure the complete resection of the mesentery of the transverse colon.

Variations in Laminar Arrangements of the Mesocolon and Retropancreatic Fascia: a Histological Study Using Human Fetuses Near Term.

OBJECTIVE: The embryonic mesentery of the ascending and descending colons as well as the pancreas disappears due to peritoneal fusion, but there might be no or few photographic demonstrations of the intermediate morphologies during the process. The aims of this study were to characterize the morphological relationship of the interface between the renal fascia and peritoneum. METHODS: Fourteen late-stage fetuses with crown rump lengths (CRLs) of 250-325 mm (gestational age: 30-38 weeks) were histologically examined. RESULTS: The renal fascia, a thick or thin layer consisting of densely-distributed abundant fibers, was consistently separated from the renal capsule by a perirenal space containing fat. The transverse colon carried a typical mesocolon histologically different from the renal fascia. The ascending and descending mesocolons were irregularly divided into multiple laminae and the colic external longitudinal muscle appeared to directly contact the renal fascia. There was a spectrum of variations from multiple laminae to a single thick fascia between the pancreatic body and the left kidney or adrenal. CONCLUSIONS: A fascial development after retroperitoneal fusion of the mesentery showed great individual and site-dependent differences in proportion of 1) a complete fusion with the renal fascia and 2) a multilaminar structure including the remnant peritoneum. These variations masked the likely stage-dependent change.

Complete mesocolic excision for colonic cancer.

INTRODUCTION: Complete mesocolic excision for colonic cancer is similar in concept to total mesorectal excision for rectal cancer. This review aims to provide the embryological and anatomical rationale behind CME, and to review the current literature on CME, relative to the feasibility via laparoscopy, the oncological adequacy and outcomes. EVIDENCE ACQUISITION: A literature search was performed at the end of 2017 according the PRISMA guidelines for systematic reviews. Of 3980 articles found, we analyzed 96 articles. Of note, many case series had overlapping populations; there were five review articles, two consensus conference proceedings, six comparative but only one randomized trial. EVIDENCE SYNTHESIS: The embryonic and anatomical rationale is well described. CME is feasible via laparoscopy, which may facilitate dissection and anatomic precision: no statistically significant differences were found when compared to open CME regarding overall survival. However, morbidity may be higher in the hands of non-expert laparoscopic surgeons. CONCLUSIONS: Oncological adequacy can be obtained with laparoscopic CME, with increased lymph node retrieval. However, until now, there is no formal proof that CME improves local recurrence or survival.

Anatomy of the Transverse Mesocolon Based on Embryology for Laparoscopic Complete Mesocolic Excision of Right-Sided Colon Cancer.

BACKGROUND: To treat colon cancer via complete mesocolic excision (CME) with central vascular ligation (CVL), dissection along the embryologic fusion planes is required. However, this surgery is difficult, especially for right-sided colon cancer, because the anatomy and embryology of the transverse mesocolon are not familiar to gastrointestinal surgeons. METHODS: In this video article, the anatomic details of the transverse mesocolon based on embryology are illustrated with a focus on the venous anatomy. Dissection of the transverse mesocolon along the embryologic planes using a cranial approach during laparoscopic right hemicolectomy also is presented. RESULTS: During the development of the primitive gastrointestinal tract, the transverse mesocolon locates between the terminal portion of the midgut and the beginning of the hindgut. After 270° counterclockwise rotation of the primary intestinal loop, the transverse mesocolon fuses with the frontal surface of the duodenum and pancreas. Simultaneously, the greater omentum hangs down from the greater curvature of the stomach in front of the transverse colon and fuses with the transverse mesocolon. Moreover, the drainage vein of the right colon sometimes joins the right gastroepiploic vein, and the gastrocolic trunk is formed. Anatomic complexity of the transverse mesocolon is caused by rotation and fusion of the gastrointestinal tract during embryologic development. CONCLUSIONS: Knowledge concerning these embryologic peculiarities of the transverse mesocolon should be useful in the performance of laparoscopic CME with CVL for right-sided colon cancer.

Complete mesocolic excision an assessment of feasibility and outcome.

Surgery is the most important factor for radical treatment of colon cancer, and the long-term prognosis can be improved by improving the surgical treatment without increased risk of perioperative mortality. Complete mesocolic excision (CME), in which more extensive lymph node (LN) dissection is performed, has been shown in single-centre studies with historical controls to be associated with better oncological outcome. However, better evidence is needed. The main purpose of this PhD thesis was to investigate whether CME could be implemented in a colorectal surgical department in Denmark, whether more extensive dissection could demonstrate LN metastases outside the mesocolon, and to demonstrate a possible association between CME and improved oncological results without increased risk of perioperative mortality. This thesis includes five articles. Two articles (IV and V) are based on the population of patients undergoing elective resection for colon cancer in the Capital Region from June 2008 to December 2013. Two articles (II and III) are based on data from the local colon database in Hillerød, and the last article (I) is a systematic review concerning the risk of metastases from colon cancer to the central LNs in the mesocolon. Article I found a risk of metastases in central LNs to be reported in 1-22% of the cases of right-sided colon cancers, and in up to 12% of the cases with sigmoid tumours. The populations included and methods used in the studies were very heterogeneous and no definitive conclusions can be drawn. It was shown in article II that the surgical quality, i.e. quality of the specimens assessed by the pathologists, improved with implementation of CME in Hillerød. The vascular tie was higher, and the implementation was not associated with an increased risk of perioperative mortality. Article III demonstrated a risk of LN metastases in the gastrocolic ligament along the stomach for tumours located in the transverse colon, in the ascending or descending colon close to or in the flexures. It occurred in 4% of all patients and 13% of the patients with LN metastases in mesocolon. Resection of these LNs seems advisable for these tumour locations. Article IV showed no association between increased perioperative mortality and CME (n = 529) when compared with non-CME (n = 1,701). The 30-day mortality was 4.2% after CME compared with 3.7% after non-CME (p = 0.605), and the 90-day mortalities were 6.2% and 4.9% (p = 0.219) respectively. Odds ratios for 30-day and 90-day mortalities after CME were respectively 1.07 (95% confidence interval: 0.62-1.80) and 1.25 (0.77-1.94) in the multi-variable logistic regression analyses. Postoperative respiratory failure and need for vasopressors were significantly more frequent in the CME group and, besides CME itself, could be associated with the fewer laparoscopic resections and more severe preoperative comorbidity in the CME Group. Article V demonstrated an association between higher four-year disease-free survival for stage I-III tumours and CME (n = 364) when compared with non-CME (n = 1,031). Most notable was the difference for stage I and II cancers. The four-year disease-free survival for stage I was 100% in the CME group compared with 89.8% (83.1-96.6) in the non-CME group (p = 0.046). For stage II the disease-free survivals were 91.9% (87.2-96.6%) in the CME group and 77.9% (71.6-84.1%) in the non-CME group (p = 0.0033), and for stage III 73.5% (63.6-83.5) and 67.5% (61.8-73.2) (p = 0.13) respectively. In the multivariable Cox regression models, CME was a significant predictive factor for higher dis-ease-free four-year survival for stage I-III patients with hazard ratios (HR) for CME of 0.59 (0.42-0.83, p = 0.0025). For stage II the HR was 0.44 (0.23-0.86, p = 0.018) and for stage III 0.64 (0.42-1.00, p = 0.048).

Laparoscopic complete mesocolic excision for right-sided colon cancer using a cranial approach: anatomical and embryological consideration.

BACKGROUND: Complete mesocolic excision (CME) with central vascular ligation (CVL) should be employed for the treatment of colon cancer patients because of its superior oncological outcomes. However, this technique is technically challenging in laparoscopic right hemicolectomy because of the anatomical complexity of the transverse mesocolon. METHODS: We focused on the embryology and anatomy of the transverse mesocolon to overcome the difficulty of this surgery. The validity and efficacy of a cranial approach in achieving CME with CVL in laparoscopic right hemicolectomy was elucidated from the embryological point of view. RESULTS: In total, 28 consecutive patients with right-sided colon cancer were treated by laparoscopic right hemicolectomy using a cranial approach. There were no conversion to open surgery or switching to another approach. Using this approach, torsion and fusion of the transverse mesocolon, which occurred during embryological development, could be reversed and the complex anatomy of the transverse mesocolon could be simplified before performing CVL of colonic vessels. CONCLUSIONS: A cranial approach is considered valid and useful for CME with CVL in laparoscopic right hemicolectomy from the embryological point of view.

Fetal topohistology of the mesocolon transversum with special reference to fusion with other mesenteries and fasciae.

The developing mesocolon transversum was investigated using hematoxylin and eosin-stained semiserial sections derived from 17 human fetuses between 12 and 30 weeks of gestation. The mesocolon was attached to the mesoduodenum and greater omentum until 12 weeks. However, the fetal duodenal attachment appeared not to correspond to the right colic flexure in adults. The greater omentum and mesocolon were likely to be irregularly folded at the attachment site possibly because the developing transverse colon "ran into" and pushed up the greater omentum and pancreatic head. Lymphatic vessels invaded the indistinct fusion plane to destroy the primary configuration. Moreover, the mesocolon seemed to "seize" or take-over some parts of the splenic side of the greater omentum, but the thick gastric side containing the right gastroepiploic artery and vein remained along the greater curvature. Until 20 weeks, the left colic flexure was fixed to the pancreatic tail, and near the flexure the mesocolon also fused with the renal fascia. The left splenic end of the greater omentum was folded and fused together to form a thick ligament-like structure, i.e., the gastrocolic ligament. In addition, near the duodenojejunal junction, a peritoneal bridge was often seen containing the inferior mesenteric artery or vein. Although surgeons generally believe that the mesocolon can be gently detached from the greater omentum, the fusion plane in adults appears to be the result of secondary modification and simplification by vascular development.

Volvulus of the small intestine caused by right paraduodenal hernia: a case report.

This report describes a very rare case of right paraduodenal hernia presenting as volvulus of nonherniated small intestine. A 12-year-old boy presented with sudden onset of lower abdominal pain, and emergency laparotomy was performed on a diagnosis of small intestinal obstruction. Laparotomy confirmed right paraduodenal hernia and volvulus of the small intestine out of the hernia sac.