Familial Adenomatous Polyposis

How is FAP diagnosed?

Examination of the lower bowel requires the use of a fibreoptic tube called a flexible sigmoidoscope which passes through the rectum into the lower bowel, or sigmoid colon, approximately 60 cm. It has a light source, magnifying eyepiece, and open channel through which air may be passed to expand the colon for easier viewing and biopsy.

Introduction and Definition

Where do adenomas grow?

When do adenomas develop?

How will I know if I have FAP?

How is FAP diagnosed?

What is the treatment for FAP?

Where else can adenomas develop?

Who is at risk for FAP?

Flexible Sigmoidoscope

This test is sufficient to diagnose FAP and is initiated from the age of 10 for at-risk children of an affected parent.

Flexible sigmoidoscopy may be done in the doctor's office after a 24-hour bowel preparation. Sedation is not required. Flexible sigmoidoscopy is repeated every two years until age 40 and every 3-5 years until age 60 for each child and sibling of a person with FAP.

A more extensive view of the entire large bowel is provided with a longer tube called a colonoscope. Detailed exploration of problem areas in the large intestine may be carried out. Polyps may be biopsied or removed through the colonoscope. Light sedation is required, along with a specific bowel preparation. Colonoscopy is suggested as a screening procedure for families with atypical or attenuated FAP since adenomas may predominate in the upper part of the colon.


An x-ray of the colon and rectum is not recommended to diagnose FAP because adenomas are often very small and are easily missed or mistaken for stool particles. Moreover, if polyps are observed, the patient will have to return for a scope and biopsy to confirm the type of polyp and degree of change within the polyp.

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