Anatomical and radiological basis of extrafascial excision of the rectum

Abstract

The operation of extrafascial excision dissects directly on the rectal fascia propria to remove the rectum and mesorectum within an intact fascial envelope. The studies contained in this thesis revolve around the recent finding that if a rectal cancer is contained within the fascia propria and the rectum is removed by extrafascial excision then local recurrence of the cancer will be exceptional. The thesis is presented in 4 parts as anatomical, radiological, clinical and operative sections. Gross and microscopic examination of surgical specimens, post-mortem dissections and axial cross sectional anatomy images were used to define the anatomy of the fascia propria. It is shown to be a 150μm thick, collagen membrane completely surrounding the mesorectum. The hypogastric nerves and pelvic plexuses are embedded in the parietal fascia separated from the mesorectum and fascia propria by a loose areolar layer. A computerised three-dimensional model of the rectum and mesorectum has been generated based on 1mm axial cross sections of the anatomy of the area and axial MR scans offering the potential to visualise the rectum in its mesorectum preoperatively. A systematic review of preoperative radiological staging has been reported comparing endorectal ultrasound, CT and MR imaging. The ability to determine the relation of the tumour to the fascia propria preoperatively has, however, not been previously explored. Cadaveric studies in this thesis have demonstrated that the fascia propria can be identified by axial CT and MR imaging. In a consecutive series of 43 patients with rectal cancer preoperative MR accurately predicted the relation of the deepest tumour invasion to this fascia. In the third section extrafascial excision has been compared with conventional surgery at a single institution over a 16 year period. In a study population of 262 rectal cancer patients operated on with curative intent, extrafascial excision had a significantly lower local recurrence rate and prolonged cancer-free survival without an increase in cost or complication rates. Based on these studies a new description of the operation of extrafascial excision of the rectum is presented in the fourth section with emphasis on preventing complications. This thesis has provided a new understanding of the surgical anatomy of the rectum and a novel management protocol for rectal cancer based on the relationship of the tumour to the fascia propria as detected by preoperative MR imaging.