[Update on epidemiology and risk factors of colorectal carcinoma].

Etiology of colorectal cancer is not completely clear. Epidemiologic studies, especially those on migrant populations, demonstrate the importance of environmental factors, particularly dietary, in cancerogenesis. Anyway, familial aggregation within a given population shows that genetic factors play an important role. General risk factors are represented by age, sex, physical activity... while some pathologies increased the risk of developing KCR or are frankly precancerous (adenomas, ulcerative colitis, Crohn's disease...).