Discontinuous rectal cancer spread in the mesorectum and the optimal distal clearance margin in situ

PURPOSE: We examined the frequency, mode, and extent of discontinuous spread of rectal cancer in the mesorectum to determine the optimal distal clearance margin in situ. METHODS: Forty consecutive patients with rectal cancer undergoing locally curative resection were studied prospectively. Discontinuous cancer spread in the mesorectum and the extent of distal spread was examined microscopically. A tissue shrink-age ratio comparing the distal clearance margin measured before transection to that measured after fixation in each case, was used to convert microscopically measured extent of distal spread to extent in situ, RESULTS: Discontinuous cancer spread in the mesorectum was observed in 17 cases (43 percent); lymph node metastasis in 15 cases (38 percent) and small deposits other than nodal metastases in 8 cases (20 percent). Distal cancer spread (either intramural or mesorectal) was observed in 6 cases (15 percent), The mean distal clearance margin before transection and after fixation was 3.2 cm and 2 cm, respectively. The mean tissue shrinkage ratio was 60 percent. The maximum extent of microscopic distal spread and adjusted distal spread in situ were 20 and 24 mm, respectively. CONCLUSIONS: Excising the mesorectum with fascia propria circumferentially intact is essential for rectal surgery. The optimal distal clearance margin for the rectal wall as well as the mesorectum in situ can be reduced to 3 cm with a right angle.