Obstructing carcinomas of the colon and rectum have a smaller size compared with those of non-obstructing carcinomas.

The aim of the current study was to elucidate the histopathological characteristics of obstructing carcinoma of the colon and rectum. We studied 72 patients with colorectal carcinoma, including 13 with obstructing carcinoma. The obstruction carcinomas occurred in sigmoid colon significantly more frequently than did non-obstructing carcinomas (p=0.007). The mean size of the obstructing carcinomas was 3.7+/-0.9 cm, which was significantly smaller than that of non-obstructing carcinomas (5.4+/-1.9 cm, p=0.003). The proportion of lymph node metastasis in obstructing carcinomas was 66.9%, which was significantly higher than that in non-obstructing carcinomas (42.4%, p=0.021). The proportion of carcinomas classified into Dukes' C or D in obstructing carcinomas was 84.6% and was significantly higher than that in non-obstructing carcinomas (52.5%, p=0.026). The pathogenesis of obstruction in colorectal carcinoma can be also derived from the contraction of the intestinal lumen caused by the condensation of cancer cells.