【Abstract】ObjectiveTo study the distal intramural spread of rectal carcinoma, and provide evidence for modification of rectal carcinoma surgery. MethodsSixty patients with rectal carcinoma admitted to the first affiliated hospital of Chongqing university of medical science from November 2001 to October 2002 were included. The specimens were extended to its original size and shape by the fat clearing method. Mesenteric lymph nodes were dissected by using transillumination to examine metastases histologically, then a lymph nodes map was produced which including the site of the primary lesion, the vascular distribution, and the sites of dissected nodes. The specimen below the distal margin of the tumor was cut continuously with 0.5 cm interval then sectioned for histopathological examination. ResultsTumor spread to the distal intramural was observed in 11 of 60 patients (18.3%) with the range within 1.5 cm, of which less than 0.5 cm in 5 case, 5 cm to 1.0 cm in 2 cases, 1.0 cm to 1.5 cm in 4 cases. The tumor invasion was correlated with gross type, histological type and infiltrative depth, but not with sex, age, location of the tumor, size of the tumor, lymph nodes metastases and Dukes stage. Conclusion The range of distal mural excision should exceed 1.5 cm to tumor margin in radical surgery for rectal carcinoma. This rule should be emphasized for patients with poor cell differentiation and deep infiltration.