[Anatomic study and clinical practice of mesopancreas and total mesopancreatic excision]

Objective: To explore the anatomical characteristics of the mesopancreas, to define the range of the total mesopancreas excision and to evaluate the feasibility, safety and effectiveness in the treatment of pancreatic cancer. Methods: A regional anatomical and pathological study was performed on 14 cadavers with large slices and paraffin sections. The clinical and pathological data of 58 consecutive patients underwent total mesopancreas excision for pancreatic head carcinoma from January 2013 to December 2015 were prospectively collected and analysed. The perioperative morbidity, mortality and clinical outcomes of patients underwent total mesopancreas excision were compared with the patients underwent conventional pancreaticoduodenectomy from January 2010 to December 2012. Results: The mesopancreas located in the retropancreatic area, extending from the head, neck, and uncinated process of pancreas to the aorto-caval groove, in which there were loose areolar tissue, adipose tissue, nerve plexus, lymphatic and capillaries. Although no fibrous sheath or fascia like mesocolorectum was found around the structures, a relatively fixed extent could be defined according to its embryologic and anatomic characters. In clinical practice, total mesopancreas excision was classified into two levels according to the extent of resection in this series: level Ⅰ was a"standard total mesopancreas excision" or"total mesopancreas excision in a narrow sense" , which was similar to the extent of standard resection from consensus statement of ISGPS. Level Ⅱ was defined as any procedure extending the range of level Ⅰ, called the"extended total mesopancreas excision" or"total mesopancreas excision in a broad sense". In TMpE group, the intraoperative blood loss( (461.4±184.5)ml vs. (532.2±319.8)ml, P=0.301), operation time( (368.6±92.5)minutes vs. (397.1±112.7)minutes, P=0.559), total complication rate (39.7% vs. 51.2%, P=0.250), fistula mortality (25.9% vs. 30.2%, P=0.628) were all reduced. There were significantly higher R0 rate (91.4% vs.76.7%, P=0.041) and more harvested lymph nodes (16.2 vs. 11.4, P=0.000) and lower total and local recurrence: rate (half-year local recurrence rate: 7.8% vs. 23.7%, P=0.036; one-year local recurrence rate: 18.2% vs. 39.5%, P=0.018) and longer disease-free survival (16.9 months vs. 13.4 months, P=0.044) and overall survival(22.5 months vs. 19.9 months, P>0.05) were also found in the study group. Conclusions: Mesopancreas is different from mesorectum since it has no fascial envelop, which should be regarded as a surgical concept, rather than an anatomical structure. Total mesopancreas excision is safe and feasible for pancreatic head cancer and probably helps to increase the R0 resection rate and improve the clinical outcomes.