What is the recommended colonoscopy screening schedule for a young individual with familial adenomatous polyposis (FAP)?

Colonoscopy Screening for Familial Adenomatous Polyposis

For young individuals with classic FAP, begin flexible sigmoidoscopy or colonoscopy at age 10-15 years and repeat annually until colectomy is performed. 1

Initial Screening Protocol

Start surveillance between ages 10-15 years using either flexible sigmoidoscopy or colonoscopy, depending on institutional preference and family phenotype. 1 The British Society of Gastroenterology recommends starting at age 12-14 years, while ASCO and ESMO guidelines suggest age 10-11 years for classic FAP. 1

• Annual screening is mandatory once surveillance begins and must continue until prophylactic colectomy is performed. 1
• Once adenomas are detected, switch to full colonoscopy annually if sigmoidoscopy was initially used, to ensure complete visualization of the entire colon. 1

Timing of Genetic Testing

Perform genetic testing 1 year before initiating endoscopic surveillance (around age 9-14 years), assuming the familial APC mutation has already been identified in an affected relative. 1 This allows time for counseling and planning before the first procedure.

• Genetic testing should only proceed after the pathogenic APC mutation is confirmed in the affected family member. 1
• If the child tests negative for the familial mutation, they can follow average-risk screening guidelines. 1

Attenuated FAP Variant

For attenuated FAP (AFAP), the screening protocol differs significantly:

• Begin colonoscopy at age 18-20 years (not age 10-15). 1
• Repeat every 1-2 years until adenomas are detected, then increase to annual colonoscopy. 1
• AFAP presents with fewer polyps (typically 10-100) and later onset compared to classic FAP. 1, 2

Post-Colectomy Surveillance

After prophylactic colectomy (typically performed in late teens to early twenties):

• Surveillance of remaining rectal tissue or ileal pouch every 6-12 months if any rectal tissue remains. 1
• If an ileoanal pouch was created, surveillance intervals range from every 6 months to 5 years depending on polyp burden. 1

Upper Gastrointestinal Surveillance

Begin gastroduodenal endoscopy at age 25-30 years or when colorectal polyposis is diagnosed, whichever comes first. 1

• Use both forward-viewing and side-viewing endoscopes to adequately visualize the ampulla of Vater. 1
• Surveillance intervals are determined by Spigelman staging (ranging from 6 months to 5 years). 1
• Duodenal cancer becomes the leading cause of mortality after colectomy. 1, 2

Critical Pitfalls to Avoid

Do not delay screening beyond age 15 years in known or suspected classic FAP cases, as colorectal cancer can develop in the teenage years if polyps are left unmonitored. 1, 2, 3

Do not use 5-year intervals for FAP surveillance—this is appropriate only for family history screening, not for confirmed FAP gene carriers. 1

Do not stop surveillance after colectomy—lifelong monitoring of the remaining rectum/pouch and upper GI tract is essential. 1, 2

Extracolonic Surveillance

Additional screening for FAP-associated manifestations:

• Thyroid surveillance: Annual cervical palpation or ultrasound starting at age 15-30 years. 1
• Hepatoblastoma screening: Abdominal ultrasound and serum AFP every 4-6 months from early infancy until age 7 years (only in young children with FAP). 1
• Desmoid tumor monitoring: Annual physical examination after colectomy or other surgery, with CT/MRI if positive family history of desmoids. 1

Surgical Timing

Prophylactic colectomy is strongly recommended between ages 16-25 years to prevent inevitable colorectal cancer development, as individuals with untreated FAP carry a 100% lifetime risk of colorectal cancer. 4, 2 Surgery should be performed when polyp burden becomes unmanageable endoscopically or when high-grade dysplasia is detected. 1