Research has not yet led to a definitive etiology. Excessive animal protein/fat diet (excessive meat consumption), lack of dietary fiber intake (low consumption of fruits and vegetables), and lack of physical activity are considered high risk factors for the development of rectal cancer. Familial intestinal polyposis, which has been recognized as a precancerous lesion. Adenoma, a history or family history of colorectal cancer, ulcerative colorectitis, schistosomiasis, and patients with a history of pelvic radiation therapy are also considered to be at high risk for rectal cancer. There is no definite conclusion on whether there is any relationship between constipation and the occurrence of (colo)rectal cancer.