Also, every three to five years you would receive a sigmoidoscopy and a double contrast barium enema to look at the lower part of the bowel.

We obtained supportive evidence for this explanation from a double contrast barium enema investigation of a patient complaining of changed bowel habit.

Radiology of the small intestine and either double contrast barium enema or colonoscopy were used to determine the anatomical distribution of disease.

Control subjects as well as patients with cancer or polyps underwent rigid sigmoidoscopy and colonoscopy or double contrast barium enema.

After the indium-111 and 51-chromium excretion studies all patients had a full colonoscopy or double contrast barium enema to confirm the diagnosis and to evaluate the extent of disease.

In addition, three other less-invasive tests - the fecal occult blood test, a double contrast barium enema and digital rectal exams - can catch many cancers, though none are as effective as colonoscopies.

The current American Cancer screening guidelines for colon cancer in an average risk patient begin at the age of 50 and include: testing of stool samples for traces of blood yearly, a flexible sigmoidoscopy every 5 years, a double contrast barium enema every 5 years, and a colonoscopy every 10 years.