If i have blood and mucus why is no further testing done after a sigmoidoscopy? what part of bowel are cancers common?

Depends : Why did you have sigmoidoscopy? A significant bowel cancer risk factor is genetics (do GI cancers run in your family?) & medical history (do you have inflammatory bowel disease like ulcerative colitis?). Also, has your physician found a different explanation for your symptoms? No for the 1st 2 questions & Yes for the last puts you at low cancer risk. Do discuss this with your primary clinician.

Colonoscopy : if you're still having significant bleeding you may want to let your physician know. They could do a colonoscopy for a more complete evaluation.

Not normal: Blood in the stool is not normal and needs to be explained. Causes can range from local irritation, anal fissure ( crack in the tissue), hemorrhoid, polyp, to cancer. Colonoscopy will examine more tissue than sigmoidoscopy. Ask your doctor if the cause of bleeding has been established. If not, further testing is needed.

Plenty: There are more tests such as a colonoscopy that can check for more spots where the blood and mucous are coming from. Intestinal cancer is rare in the small intestine but can happen there including the large intestine and rectum. Please see your doctor for more answers. Cheers.

Call your Dr: Cancer of the colon increases in frequency after age 50. Rectal bleeding is more often due to cancers in the transverse and left colon. Early cancers in the right colon are unfortunately difficult to detect even on colonoscopy. If blood is noticed at the end of defecation it is more likely to be hemorrhoidal bleeding. You should speak with your physician. Did he see bleeding hemorrhoids?