Large intestinal carcinoma, one of the commonly encountered malignant tumors, refers to carcinoma of colon and rectum. It is also called anal carcinoma when the lesion is at the anus. The incidence and mortality rank the 4th- 6th in the malignant tumors. There are more male patients than female patients with a ratio of 1.1 - 3.4: 1. It mainly affects the patients aged 30 - 50, mostly around 45, but it is also common in patients younger than 30.The cancer is most commonly found in rectum and sigmoid colon which occupies a percentage of 77.8 %, followed by the tumors in the cecum and ascending colon and less common in hepatic flexure and splenic flexure of the descending colon.

The growth of the large intestinal carcinoma is slow and the metastasis of the cancer occurs late. Most of the metastasis occurs at the anal canal, rectum and the junction of rectum and sigmoid colon. At present, it is still difficult to make an early diagnosis of the disease. The post-operative survival rate of 5 years is rather low. The pathogenesis of this disease is complicated. It is believed to be related to the chronic inflammation, polyp and adenoma of the large intestine, diet and environmental factors.