colon cancer symptom : Colorectal Polyps

A polyp is a growth of tissue from the intestinal or rectal wall that protrudes into the intestine or rectum and may be noncancerous or cancerous. Polyps vary considerably in size; the bigger the polyp, the greater the risk that it is cancerous or precancerous. Polyps may grow with or without a stalk; those without a stalk are more likely to be cancerous than those with a stalk. Adenomatous polyps, which consist primarily of glandular cells that line the inside of the large intestine, are likely to become cancerous (that is, they are precancerous).

Some polyps are the result of hereditary conditions, such as familial polyposis, Gardner's syndrome, and Peutz-Jeghers syndrome. In familial polyposis, 100 or more precancerous polyps develop throughout the large intestine and rectum during childhood or adolescence. In nearly all untreated people, the polyps develop into cancer of the large intestine or rectum (colorectal cancer) before age 40. In Gardner's syndrome, various types of noncancerous tumors develop elsewhere in the body (for example, on the skin, skull, or jaw) in addition to the precancerous polyps that develop in the large intestine and rectum. In Peutz-Jeghers syndrome, small lumps called juvenile polyps develop in the stomach, small intestine, large intestine, and rectum. These polyps develop before birth (in utero) or during early childhood. Although polyps in Peutz-Jeghers syndrome do not increase the risk of developing cancer of the intestinal tract, people with Peutz-Jeghers syndrome do have an increased risk of developing cancer of the pancreas, breast, lung, ovary, and uterus.

Symptoms and Diagnosis

Most polyps do not cause symptoms. When they do, the most common symptom is bleeding from the rectum. A large polyp may cause cramps, abdominal pain, or obstruction. Large polyps with fingerlike projections (villous adenomas) may excrete water and salts, causing profuse watery diarrhea that may result in low levels of potassium in the blood (hypokalemia). Rarely, a rectal polyp on a long stalk drops down and dangles through the anus. People with Peutz-Jeghers syndrome have brown skin and brown mucous membranes, especially of the lips and gums.

A doctor may be able to feel polyps by inserting a gloved finger into the rectum, but usually polyps are discovered during flexible sigmoidoscopy (examination of the lower portion of the large intestine with a viewing tube). If flexible sigmoidoscopy reveals a polyp, colonoscopy is performed to examine the entire large intestine. This more complete and reliable examination is performed because more than one polyp is usually present and may be cancerous. Colonoscopy also allows a doctor to perform a biopsy (removal of a tissue sample for examination under a microscope) of any area that appears cancerous.

http://www.merck.com/mmhe/sec09/ch131/ch131h.html