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

PURPOSE: If rectal cancer does not penetrate the fascia propria of the rect um and the rectum is removed with the fascial envelope intact (extrafascial excision), then local recurrence of the cancer will he minimal. Modern ima ging 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 p ropria and whether tumor invasion through this fascia can be identified pre operatively. METHODS: Two separate experiments were performed: 1) pelvic ma gnetic resonance imaging was performed before and after dissection and mark ing of the plane of extrafascial dissection of the rectum of a cadaver; and 2) magnetic resonance imaging was performed in 43 rectal cancer patients p reoperatively. Two radiologists independently reported the depth of tumor i nvasion in relation to the fascia propria. The tumors were resected by extr afascial excision, and a pathologist independently reported the relation of the tumor to the fascia propria. RESULTS: The marker inserted in the cxtra hscial plane showed that the plane visualized on pelvic magnetic resonance imaging was the fascia propria dissected in extrafascial excision of the re ctum. The magnetic resonance imaging detected tumor penetration through the fascia propria with a sensitivity of 67 percent, a specificity of 100 perc ent, and an accuracy of 95 percent. CONCLUSION: The surgical fascia propria can be identified on preoperative magnetic resonance imaging in patients w ith rectal cancer. Tumor invasion through this fascia can be detected on ma gnetic resonance imaging. This method of assessment offers a new way to sel ect those patients who require preoperative radiotherapy.