University:
Stanford University
Course:
MED 101 | Human Anatomy
Academic year:

2023
Views:

316

Pages:

3
Author:

larbi43100

‭Colorectal cancer‬ ‭The colon follows the ileum from the ileocaecal valve. It successively includes‬ ‭the cecum with its appendix, the ascending (or right) colon, the transverse‬ ‭colon, the descending (or left) colon and the sigmoid colon which ends in front‬ ‭of the third vertebra of the sacrum to continue through the rectum.‬ ‭The walls of the colon are made up of 4 concentric layers: the mucosa (deep),‬ ‭the submucosa, the muscularis and the serosa (superficial).‬ ‭In 2010, 142,570 people were diagnosed with colorectal cancer in the United‬ ‭States and 51,370 people died from it. The lifetime risk of developing colorectal‬ ‭cancer is 5 to 6%.‬ ‭Sex ratio‬‭-The disease is observed a little more in‬‭men than in women (sex ratio‬ ‭= 1.2).‬ ‭Age at diagnosis‬‭-The disease affects people aged 50‬‭and over (most‬ ‭often between 60 and 70).‬ ‭Geographic factors‬‭-The risk of colorectal cancer is‬‭higher in industrialized‬ ‭countries.‬ ‭Dietary factors‬‭-This is an extremely controversial‬‭issue. Diets high in fat and/ or‬ ‭low in fiber are thought to promote colorectal cancer, but we will discuss this‬ ‭hypothesis in more detail in the section on principles of treatment‬ ‭(chemoprophylaxis). However, we know that 1) animal fats increase the‬ ‭proportion of anaerobes in the intestinal flora, which leads to a conversion of‬ ‭normal bile acids into carcinogens, 2) the increase in serum cholesterol‬ ‭increases the risk of colorectal adenomas, 3) the increase in food calories is a‬ ‭source of obesity, therefore of insulin resistance, and therefore of an increase in‬ ‭IGF-I (Insulin-like Growth Factor I) which probably stimulates intestinal‬ ‭proliferation.‬ ‭Polyps‬‭-Among the many types of polyps that can be‬‭observed in the intestine,‬ ‭adenomatous polyps are certain precancerous conditions. Although very‬ ‭common from adulthood (30% of adults and 50% of elderly people present‬ ‭them and only seem to progress towards neoplastic transformation in less than‬ ‭1% of cases. Some anatomohistological characteristics of these polyps have a‬ ‭prognostic factor:‬ ‭-‬ ‭sessile forms are more dangerous than pedunculated forms;‬ ‭ olyps‬‭of‬‭a‬‭villous‬‭nature‬‭degenerate‬‭3‬‭times‬‭more‬‭than‬‭those‬‭of‬‭a‬ p ‭tubular nature;‬ ‭-‬ ‭the‬ ‭diameter‬ ‭of‬‭the‬‭polyp‬‭is‬‭proportional‬‭to‬‭its‬‭potential‬‭for‬‭malignant‬ ‭degeneration:‬ ‭less‬ ‭than‬ ‭2%‬ ‭for‬‭less‬‭than‬‭1.5‬‭cm;‬‭2‬‭to‬‭10%‬‭for‬‭1.5‬‭to‬ ‭2.5 cm; 10% for more than 2.5 cm.‬ ‭-‬ ‭Juvenile polyps and hyperplastic polyps are not precancerous conditions.‬ ‭Colorectal inflammatory lesions‬‭-Chronic inflammatory bowel diseases‬ ‭constitute precancerous conditions, particularly ulcerative colitis in its pancolic‬ ‭form (low risk in the first years, but increased risk of 0.5 to 1% per year‬ ‭thereafter).‬