The "meso" of the rectum and the "meso" of the pancreas: similar terms but distinct concepts in surgical oncology

A correspondence between the "meso" of the rectum and of the pancreas has recently been reported. Here we highlight the differences between mesorectum and mesopancreas. Based on anatomical findings from a series of 89 consecutive pancreaticoduodenectomies and 71 consecutive total mesorectal excisions, we observed that in contrast to the mesorectum, the mesopancreas did not have well-defined anatomic boundaries and was continuous and connected through its components with the para-aortic area. In rectal cancer,tumor deposits and nodal involvement could be confined to the mesorectum(i.e., within the mesorectal fascia), whereas in pancreatic carcinoma, tumor deposits and nodal metastases occurred in the boundless mesopancreatic area. Total mesorectal excision was made en bloc with the rectum by dissecting along the mesorectal fascia; this was not the case for mesopancreatic excision since anatomical demarcation of the mesopancreas did not exist. Moreover, the growth pattern of pancreatic cancer showed greater dispersion, which was more prominent at the invasive front of the tumor and could potentially affect the status of the resection margin. These findings indicate that the mesorectum and mesopancreas are completely distinct from the pathological, surgical, and oncological standpoints.     

Total Mesorectal Excision Results in Low Local Recurrence Rates in Lymph Node-Positive Rectal Cancer

PURPOSE: Most series report lymph node involvement as the main predictor for local recurrence. The principal lymphatic drainage of the rectum is to nodes in the mesorectum and then nodes along the superior rectal and inferior mesenteric arteries. If total mesorectal excision provides adequate block dissection of the lymphatics of the rectum, good local control with low rates of local recurrence should be achieved even in node-positive disease.METHODS: Prospective data on all rectal cancers have been collected since 1978; 170 patients with Dukes C rectal cancer have undergone anterior resection and total mesorectal excision. We did not perform any internal iliac node dissections. Follow-up data were analyzed for local recurrence and distant recurrence.RESULTS: The local recurrence rate was 2 percent for Dukes A cases, 4 percent for Dukes B, and 7.5 percent for Dukes C (P = 0.0127). The systemic recurrence rate was 8 percent for Dukes A, 18 percent for Dukes B, and 37 percent for Dukes C (P = 0.0001).CONCLUSIONS: If surgical priority is given to the difficult task of excision of the whole mesorectum, anterior resection with total mesorectal excision in node-positive rectal cancer, local recurrence rates of < 10 percent can be achieved.Presented at the Association of Colorectal Surgeons of Great Britain and Ireland, Harrogate, United Kingdom, June 25 to 27, 2001.     

Local recurrence after curative resection of cancer of the rectum without total mesorectal excision

PURPOSE: The aim of this article was to examine local recurrence after curative resection for carcinoma of the rectum in which the surgical technique of total mesorectal excision was not performed. METHODS: A single surgeon managed the patients and the data collected prospectively. Total excision of the distal mesorectum was not performed in the upper third or mid rectum. RESULTS: From 1969 to 1993 curative resections were performed in 549 patients, of which 17 died postoperatively, leaving 532 for analysis. Sphincter-saving resection was performed in 468 patients (88 percent) and abdominoperineal excision in 58 (10.9 percent). The pathology stages (Dukes) were A, 158 (29.7 percent); B, 184 (34.7 percent); and C, 190 (35.7 percent). Five hundred seventeen patients (97.2 percent) were followed up for a minimum of five years. The median period of follow-up was 82 months. Local recurrence confined to the pelvis occurred in 17 patients, and local recurrence associated with distant metastases occurred in 24 patients. The total five-year local recurrence rate was 7.6 percent. Local recurrence was increased in Stage C tumors (P=<0.0001). Diathermy dissection in the pelvis was associated with a decreased local recurrence rate (P=0.023). The five-year survival rate in curative resections was 72.5 percent. CONCLUSIONS: It is essential that articles presenting local recurrence rates should include both local recurrence in isolation and that which occurs with distant metastases. Although total mesorectal excision for rectal cancer was not performed in this study, the local recurrence rate is not materially different from that in several articles where total mesorectal excision has been used. Whether the distal mesorectum needs to be pursued in mid-rectal cancer is not yet proven.     

Total Mesorectal Excision: The Unrecognized Pelvic Plane

Total mesorectal excision for low rectal cancers has been shown to reduce local recurrence rate after curative operation to < 5 percent. The lack of anatomic appreciation of the mesorectum is an important cause of intersurgeon variability in the outcome of rectal cancer surgery. Surgical illustrations depicting the mesorectal anatomy, however, are less than accurate. Basic surgical concepts must be illustrated correctly to be learned correctly. True-to-life illustration is the only way the learner can appreciate the actual situation and improve his/her surgical results. We describe the mesorectal anatomy with correlation to computerized tomography scans of the in vivo rectum to further illustrate the technique of total mesorectal excision in rectal cancer surgery.     

Mesorectal Lymph Nodes: Their Location and Distribution Within the Mesorectum

PURPOSE: Total mesorectal excision is an alternative surgical approach for resectable rectal cancer and is associated with favorable results and a low rate of local recurrence. Despite the popularity of this technique, few data exist regarding the location and distribution of lymph nodes within the rectal mesentery. The purpose of this study was to define the distribution, size, and location of lymph nodes within the mesorectum and on the pelvic side wall. METHODS: Seven fresh cadavers at our institution's Fresh Tissue Dissection Laboratory were studied. The rectum, its mesentery, and all fatty tissue from both pelvic side walls were removed and placed in a lymph node clearing solution for 24 hours. After appropriate dissection, the distribution, size, and location of lymph nodes within the rectal mesentery and pelvic side wall tissue were documented. RESULTS: A total of 174 lymph nodes were identified (approximately 25 per patient). The majority (>80 percent) of lymph nodes were smaller than 3 mm in diameter. Fifty-six percent of the nodes within the rectal mesentery were located in the posterior mesentery, and most were located in the upper two-thirds of the posterior rectal mesentery. CONCLUSIONS: The majority of perirectal lymph nodes are small. There are few lymph nodes within the mesentery of the lower third of the rectum and relatively few in the right and left lateral portions of the mesorectum. We confirm that the majority of nodes are located in the proximal two-thirds of the posterior rectal mesentery. It is possible that removal of these nodes is responsible for the superior oncologic results found with total mesorectal excision in contrast to more traditional surgical techniques.     

Mesorectal Grades Predict Recurrences After Curative Resection for Rectal Cancer

PURPOSE: Local recurrence after curative excision for rectal cancer is frequently regarded as a failure of surgery. The macroscopic quality of the excised mesorectum after total mesorectal excision has been proposed as a means of assessment of the adequacy of surgery. This study was designed to determine the utility of mesorectal grading in prediction of local and overall recurrence after curative surgery. METHODS: All patients undergoing resection for primary adenocarcinoma of the rectum had a mesorectal grading prospectively applied to their resection specimens, according to the classification proposed by Quirke et al. (Grades 1-3; 3 is the best). The outcome of patients undergoing potentially curative surgery from 2001 to 2003 was reviewed. Prognostic significance of mesorectal grades was determined by multivariate regression analyses. RESULTS: A total of 130 patients with a median follow-up of 26 (range, 17-42) months were studied. The local and overall recurrences were 8.4 and 15 percent, respectively. The mesorectum was reported as Grade 3 in 61 patients (47 percent), Grade 2 in 52 patients (40 percent), and Grade 1 in 17 patients (13 percent). Patients with Grade 1 mesorectum had 41 percent local recurrence and 59 percent overall recurrence, respectively. However, patients with Grade 2 and Grade 3 mesorectum had 5.7 and 1.6 percent local recurrences, respectively, and 17 and 1.6 percent overall recurrence, respectively. By Cox's regression analysis, grade of mesorectum independently influenced both local and overall recurrences. CONCLUSIONS: The macroscopic quality of mesorectum after curative excision of rectal cancer is an important predictor of local and overall recurrences. The mesorectal grades may be of value in decisions regarding postoperative adjuvant therapy.     

Vascular organization in the mesorectum: angiography of rectal resection specimens

The technical advances in rectal cancer surgery are known as the total mesorectal excision. The resection in an anatomically defined plane under direct vision and with sharp dissection distinguishes it conventional rectal surgery. The result must be a complete mesorectum without deep gouges. We performed specimen angiography to confirm completeness of the removed mesorectum. Thirteen total mesorectal excision specimens were examined by angiography after continence-preserving resection of rectal carcinoma. In 11 of the 13 cases the vascular supply was exclusively via the superior rectal artery. In two cases with hypoplastic left terminating branches of the superior rectal artery there was additional perfusion via a caudally ascending vessel or via smaller vessels connected laterally. In all specimens both arterial supply and venous outflow were located within the mesorectal fascial sheath. There was no radio-opaque substance leaking from the mesorectal surface in the case of a complete mesorectal specimen. Tiny vascular branches running laterally occurred in 7 of the 13 cases. We found no larger vascular connections branching off in the lateral direction. The rectal blood supply comes almost exclusively through the superior rectal vessels. Thus the fascia covering the mesorectum forms, as far as rectal vascularization is concerned, a closed compartment. The mesorectal vessels are enclosed in the fibrous avascular mesorectal fascia. They run close above the fascia. In the case of an incomplete mesorectal excision the specimen angiography shows a stain leaking from the mesorectal fascia. Our method can be used to confirm the completeness of the removed mesorectum.     

Recent progress in diagnosis and treatment of rectal cancer]

Rectal cancer is an emerging health issue in Korea because its incidence is rapidly increasing with changes in life styles and diets. The optimal treatment of rectal cancer is based on multimodality. Among them, surgical treatment is the corner-stone. In the past, local recurrence rate has been reported as high as 30-40%, but the concept of total mesorectal excision (TME) lowered the rate of local recurrence down to less than 10%. TME focuses on sharp pelvic dissection and complete removal of rectal cancer with surrounding mesorectum inside the rectal proper fascia. TME is now considered as a standard procedure for surgical treatment of mid and low rectal cancer. With the introduction of pelvic magnetic resonance imaging (MRI) for preoperative staging of rectal cancer, risk factors for local recurrence can be predicted before surgery to distinguish patients who are in high risk for recurrence that requires preoperative neoadjuvant chemoradiation therapy. Early rectal cancer was assessed by transrectal ultrasonography (TRUS) and endorectal MRI with coil. Transanal local excision can be applied with anal sphincter preservation safely. Neoadjuvant chemoradiation therapy was performed in patients with locally advanced rectal cancer, and this resulted in tumor size reductions and histopathologic downstaging effect. As far as the quality of life is concerned, sexual and voiding function are much improved by techniques preserving nerve. Many experts have dealt with challenging practical problems of managing rectal cancer from diagnosis to quality of life. This issue contains recent progresses in the diagnosis and treatment of rectal cancer which will serve as a comprehensive reference for those who manage rectal cancer in their medical practice.     

Role of total mesorectal excision and of circumferential resection margin in local recurrence and survival of patients with rectal carcinoma

Rectal cancer is a common disease with poor prognosis because of local recurrence and metastases. Local recurrence arises mainly as a result of incomplete surgical resection. Evaluation of completeness of the mesorectum provides significant information about prognosis. Total mesorectal excision (TME) has become the surgical treatment of choice for rectal cancer because adopting the principles of TME achieves very low local recurrence rates. The adoption of the TME principles along with the estimation of the circumferential resection margin on the non-peritonealized surface of the resected rectal specimen are the most important predictors of local recurrence.     

Identification of the fascia propria by magnetic resonance imaging and its relevance to preoperative assessment of rectal cancer

PURPOSE: If rectal cancer does not penetrate the fascia propria of the rectum and the rectum is removed with the fascial envelope intact (extrafascial excision), then local recurrence of the cancer will be minimal. Modern imaging techniques have identified a fascial plane surrounding the rectum and mesorectum, and it has been suggested that this is the fascia propria. The aim of this study was to identify whether this plane is the rectal fascia propria and whether tumor invasion through this fascia can be identified preoperatively. METHODS: Two separate experiments were performed: 1) pelvic magnetic resonance imaging was performed before and after dissection and marking of the plane of extrafascial dissection of the rectum of a cadaver; and 2) magnetic resonance imaging was performed in 43 rectal cancer patients preoperatively. Two radiologists independently reported the depth of tumor invasion in relation to the fascia propria. The tumors were resected by extrafascial excision, and a pathologist independently reported the relation of the tumor to the fascia propria. RESULTS: The marker inserted in the extrafascial plane showed that the plane visualized on pelvic magnetic resonance imaging was the fascia propria dissected in extrafascial excision of the rectum. The magnetic resonance imaging detected tumor penetration through the fascia propria with a sensitivity of 67 percent, a specificity of 100 percent, and an accuracy of 95 percent. CONCLUSION: The surgical fascia propria can be identified on preoperative magnetic resonance imaging in patients with rectal cancer. Tumor invasion through this fascia can be detected on magnetic resonance imaging. This method of assessment offers a new way to select those patients who require preoperative radiotherapy.Supported by a research grant from The Maurice and Phyllis Paykel Trust, Parnell, Auckland, New Zealand.     

Studies of the vascular anatomy of the mesorectum support the concept of the total mesorectal excision

The relation between the mesorectal vessels and the mesorectal fascia needs to be clarified, as a total mesorectal excision (TME) probably derives its advantage from the fact that the visceral or mesorectal fascia can be regarded as a “tumor-tight packaging” and does not contain anatomically preformed perforations. The purpose of this investigation was to study both rectal arterial supply and vascular distribution pattern within the mesorectum. The arterial supply to the rectum was studied with the injection technique in 12 porcine and 28 human TME specimens. We stain-marked 12 porcine and 15 human specimens. Thirteen human specimens were angiographed after filling their arterial bed with a radio-opaque substance. The superior rectal artery is the main rectal artery. Terminal branches extend downwards and forward around the rectum to the level of the levator and muscle. The superior rectal artery and vein were found to be enclosed in a fibrous sheath. The main mesorectal vessels do not penetrate the mesorectal fascia. This study supports the hypothesis of bilateral somatic and one central visceral compartment in the pelvis and implies the absolute necessity of tumor removal within an intact mesorectal fascia. Received: 15 August 2000 / Accepted in revised form: 1 October 2000     

Endoscopic Posterior Mesorectal Resection After Transanal Local Excision of T1 Carcinomas of the Lower Third of the Rectum

Purpose The rectum-sparing transanal local excision is a well-established treatment of T1 carcinomas of the lower third of the rectum. A potentially increased locoregional recurrence rate by this procedure is tolerated because of the high morbidity and mortality risk of transabdominal rectal resection. Dorsoposterior extraperitoneal pelviscopy makes it possible to remove the relevant lymphatic drainage of the lower third of the rectum minimally invasively, in the sense of a rectum-sparing endoscopic posterior mesorectal resection. It has to be considered whether endoscopic posterior mesorectal resection in combination with transanal local excision allows for local radicality and an adequate tumor staging in T1 carcinomas of the lower third of the rectum, in terms of better-directed therapy planning compared with transanal local excision alone. Methods We operated on 11 consecutive patients with T1 carcinomas of the lower third of the rectum by transanal local excision in combination with endoscopic posterior mesorectal resection as a two-stage procedure in the period from 1998 to 2005. Results It was possible to perform a complete excision of the primary and to resect the posterior part of the mesorectum in all cases. Postoperative morbidity consisted of two transient neurologic complications and a pulmonary embolism. There was no mortality. Histologic analysis revealed a median of eight (range, 4–20) lymph nodes. Two patients diagnosed with lymph-node metastases received adjuvant radiochemotherapy. After a median follow-up of 48 (range, 4–60) months, there was noevidence for locoregional recurrence. In one patient liver metastasis was detected eight months postoperatively. Conclusions Radical excision of the primary tumor and an adequate tumor staging in T1 carcinomas of the lower third of the rectum seems to be achievable by means of transanal local excision and endoscopic posterior mesorectal resection.     

Total mesorectal excision and preservation of autonomic nerves]

The procedure of total mesorectal excision (TME) becomes a gold standard for the treatment of rectal cancer. The reason is the marvelously low incidence of local recurrence after TME even without other adjuvant treatment, which has been reported by several independent groups. Although controversy still exists about the role of TME in upper rectal cancer, it is now widely accepted for cancers of the middle and lower third. There are number of histopathological evidences that cancer cells can spread distally several centimeters from the lower margin of cancer, and cancer bearing lymph nodes are found in the distal portion of the mesorectal tissues far from the cancer. Therefore, the distal clearance of mesorectum should be performed downwardly to the level of pelvic diaphragm (puborectalis) and the rectum is divided within a few centimeters from the pelvic floor musculature. TME defines an en-bloc procedure, along the plane between parietal and visceral pelvic fasciae. If the dissection plane is breached, the chance of visceral pelvic fascia tearing is raised and mesorectal tissue might reside in the pelvis. There are problems in auditing the procedure. As many surgeons agree, this procedure requires a learning curve. Theoretically, the autonomic nerves run between the visceral and parietal pelvic fasciae since the nerves must be preserved to make visceral fascial envelop. Any patient who become incontinent or impotent after the surgery should have received decorticating surgery other than TME. Thus, the high quality of TME should fulfill two clinical measurements: absence of impotence or incontinence and at least single digit, 5-year, cumulative recurrence rate regardless of adjuvant therapy.     

Denonvilliers筋膜的微创解剖认识及其临床价值

1836年,法国外科学家Charles-Pierre Denonvilliers首次描述在男性的直肠与膀胱、精囊腺和前列腺之间存在薄层致密组织,后被称为Denonvilliers筋膜。1982年英国外科学家R.J. Heald教授提出全直肠系膜切除术（TME）理念,历经数十年的临床实践,TME已成为中低位直肠癌手术的金标准。根据TME理念,直肠后方及侧方均应在盆筋膜壁层内面与直肠固有筋膜间分离,而在直肠前方于Denonvilliers筋膜前方分离、肿瘤下方2 cm处倒U形离断并切除部分Denonvilliers筋膜。然而,资料显示,由于盆腔自主神经（PAN）的损伤,TME术后排尿及性功能障碍发生率居高不下。因此,进一步理清盆腔筋膜和自主神经解剖的认识,对于改善患者术后功能尤为重要。在国内外众多学者研究的基础上,我们从胚胎发育学、解剖学、组织学和外科手术角度对盆腔筋膜及外科层面进行深入探索,指出Denonvilliers筋膜不属于直肠固有筋膜的范畴、如非肿瘤浸润应予保留,并提出保留Denonvilliers筋膜全直肠系膜切除术（iTME）的理念;并采用多中心临床试验加以验证。在此基础上我们联合国内直肠癌外科领域专家,发布iTME中国专家共识,旨在提高从业者对神经功能保护的认识,规范手术操作,造福广大患者。     

Distribution of lymph nodes in the mesorectum: how deep is TME necessary?

BACKGROUND: Standardization of total mesorectal excision (TME) had a great impact on decreasing local recurrence rates for the treatment of rectal cancer. However, exact numbers and distribution of lymph nodes (LN) along the mesorectum remains controversial with some studies suggesting that few LNs are present in the distal third of the mesorectum. METHODS: Eighteen fresh cadavers without a history of rectal cancer were studied. The rectum was removed by TME and then was divided into right lateral, posterior and left lateral sides, which were further subdivided into 3 levels (upper, middle and lower). A pathologist determined the number and sizes of the LNs in each of the nine areas, b linded to their anatomical origin. RESULTS: Overall, the mesorectum had a mean of 5.7 LNs (SD=3.7) and on average each LN had a maximum diameter of 3.0 mm (SD=2.7). There was no association between the mean number or size of LNs with gender, BMI, or age. There was a significantly higher prevalence of LNs in the posterior location (2.8 per mesorectum) than in the two lateral locations (0.8 and 1.2 per mesorectum; p=0.02). The distribution of LNs in the three levels of the rectum was not significant. CONCLUSIONS: The distribution of LNs reinforces the fact that TME should always include the distal third of the mesorectum. Care must be taken to not violate the posterior aspect of the mesorectum.     

Denonvilliers’ Fascia Lies Anterior to the Fascia Propria and Rectal Dissection Plane in Total Mesorectal Excision

PURPOSE Opinion is divided whether Denonvilliers fascia lies anterior or posterior to the anatomic fascia propria plane of anterior rectal dissection in total mesorectal excision. This study was designed to evaluate this anatomic relationship by assessing the presence or absence of Denonvilliers fascia on the anterior surface of the extraperitoneal rectum in specimens resected for both nonanterior and anterior rectal cancer in males.METHODS Surgical specimens were collected prospectively from males undergoing total mesorectal excision for mid and low rectal cancer, with a deep dissection of the anterior extraperitoneal rectum to the pelvic floor. Specimens were histopathologically analyzed using best practice methods for rectal cancer. The anterior aspects of the extraperitoneal rectal sections were examined microscopically for the presence or absence of Denonvilliers fascia.RESULTS Thirty rectal specimens were examined. Denonvilliers fascia was present in 12 (40 percent) and absent in 18 specimens (60 percent). Denonvilliers fascia was significantly more frequently present when tumor involved (55 percent) rather than spared the anterior rectal quadrant (10 percent; difference between groups 45 percent; 95 percent confidence interval, 30–60 percent; P = 0.024, Fishers exact test).CONCLUSIONS When tumors were nonanterior, rectal dissection was conducted on fascia propria in the usual anatomic plane, and Denonvilliers fascia was not present on the specimen. It was almost exclusively found in anterior tumors, deliberately taken by a radical extra-anatomic anterior dissection in the extramesorectal dissection plane. Denonvilliers fascia lies anterior to the anatomic fascia propria plane of anterior rectal dissection and is more closely applied to the prostate than the rectum.Presented at the meeting of the Association of Coloproctology of Great Britain and Ireland, Brighton, United Kingdom, July 10 to 12, 2000.Reprints are not available.     

Impact of mesorectal status on local recurrence and survival in patients with rectal cancer

The main aim of this paper is to evaluate, by reviewing the most pertinent literature, both the prognostic impact of the mesorectum status in patients with cancer of the rectum and the rationale for mesorectal excision. Recent literature has been considered with special reference to the outcomes of the mesorectal surgical treatment on the relapse rate and survival. The infiltration of the mesorectum adversely affects the prognosis of the patient after a curative operation, whereas it is doubtful whether its excision per se is able to improve the prognosis. Therefore, involvement of the mesorectum may be considered to be an important indicator of already advanced and aggressive malignancy more than the true cause for the relapse. In fact, lately, some authors have pointed out that the extent of the mesorectal excision should be tailored to the specific case in order to achieve adequate and safe surgical margins and have enough prognostic information. Indiscriminate total mesorectal excision in all rectal tumours is not supported by data showing a prognostic improvement. Consequently, surgical management should be carefully planned considering the potential risks and the complications affecting this procedure. Received: 15 December 1999 / Accepted in revised form: 8 February 2000