Diagnosis at Mayo Clinic

By Mayo Clinic Staff



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You're at risk of familial adenomatous polyposis if you have a parent, child, brother or sister with the condition.

If you're at risk, it's important to be screened frequently, starting in childhood. Annual exams can detect the growth of polyps before they become cancerous. At Mayo Clinic, at-risk children who have the defective gene or whose genetic status isn't known are screened every year starting at age 10. At-risk children who don't have the defective gene are screened periodically starting at age 15.

Mayo Clinic specialists use these screening tests for FAP and its complications:

  • Sigmoidoscopy. A flexible tube is inserted into your rectum to inspect the rectum and sigmoid — the last two feet of the colon. At Mayo, sigmoidoscopy is used to screen at-risk children who haven't yet developed polyps.
  • Colonoscopy. A flexible tube is inserted into your rectum to inspect the entire colon. At Mayo, colonoscopy is used after polyps start growing and after age 18, and if attenuated FAP is suspected or already diagnosed.
  • Esophagogastroduodenoscopy (EGD) and side-viewing duodenoscopy. Two types of scopes are used to inspect your esophagus, stomach and upper part of the small intestine (duodenum and ampulla). The doctor may remove a small tissue sample (biopsy) for further study.
  • CT or MRI. Imaging of the abdomen and pelvis may be used, especially to evaluate desmoid tumors.

Genetic testing

A simple blood test can determine if you carry the abnormal gene that causes FAP. Genetic testing may also detect whether you're at risk of complications of FAP.

Mayo Clinic specialists may suggest genetic testing if:

  • You have family members with FAP
  • You have some, but not all, of the signs of FAP

Ruling out FAP spares at-risk children years of screening and emotional distress. For children who do carry the gene, appropriate screening and treatment greatly reduce the risk of cancer.

At Mayo Clinic, genetics counselors discuss the pros and cons of testing with you, including the psychological and medical implications and confidentiality issues. If you choose genetic testing, your counselor and your doctor discuss the results with you.

The Molecular Genetics Laboratory uses the latest techniques to detect specific mutations in the APC gene associated with FAP. If the initial genetic test is negative, Mayo scientists can sequence the MUTYH gene to determine if you have MUTYH-associated polyposis.

Additional tests

Mayo Clinic specialists may recommend thyroid exams and other testing to detect other medical problems that can occur if you have FAP.

Oct. 20, 2015