Approach to Young Adults with Positive FIT and Abdominal Symptoms

Immediate Management: Colonoscopy is Required

• The American Gastroenterological Association recommends proceeding directly to colonoscopy without delay for patients with positive FIT and abdominal symptoms, as FIT is not recommended for symptomatic patients due to the increased risk of advanced-stage disease 1
• Schedule colonoscopy within 30 days of presentation with alarming symptoms, with a maximum acceptable delay of 6 months, aiming for completion within 3 months 1, 2

Why This Patient is High-Risk

• Unexplained iron deficiency anemia is classified as an alarming symptom requiring colonoscopy regardless of FIT status, with a high positive predictive value for significant neoplasia 1, 3
• Positive FIT test has a high positive predictive value for significant neoplasia, with 40-47% for advanced neoplasia 1, 4
• Ongoing abdominal symptoms, in combination with anemia, elevate the risk substantially 1

Colonoscopy Quality Requirements

• The colonoscopy must be complete to the cecum and of high quality, as young patients with early-onset colorectal cancer often present with right-sided lesions 1
• Incomplete examination may miss synchronous lesions, which occur in up to 3% of cases 5

Additional Diagnostic Workup

• Confirm iron deficiency with iron studies, including serum ferritin and transferrin saturation if ferritin is equivocal 3
• Screen for celiac disease, found in 3-5% of iron deficiency anemia cases, by checking tissue transglutaminase antibodies 3
• Perform urinalysis or urine microscopy to exclude renal causes of anemia 3
• Obtain a complete blood count to document baseline hemoglobin for comparison 3

Family History Assessment

• Obtain detailed family history of all cancers, not just colorectal, as hereditary syndromes are implicated in 13% of early-onset colorectal cancer 1
• Having ≥2 first-degree relatives with colorectal cancer or ≥1 first-degree relative diagnosed before age 50-60 significantly increases risk 1

If Colonoscopy is Negative

• Perform gastroscopy to evaluate for upper GI sources of bleeding if symptoms persist or anemia recurs 3
• Obtain small bowel biopsies to exclude celiac disease if not already screened serologically 3
• Capsule endoscopy is the preferred test for small bowel examination if bidirectional endoscopy is negative and iron deficiency anemia persists or recurs 3

Common Pitfalls to Avoid

• Do not repeat FIT instead of colonoscopy, as colonoscopy is mandatory when the test is positive, with a strong recommendation and moderate-quality evidence 4, 6
• Do not delay colonoscopy for "low-risk" age, as early-onset colorectal cancer incidence is rising, and young patients often present with advanced-stage disease 1

Iron Replacement Therapy

• Initiate iron replacement therapy for anemia, with a good response confirming absolute iron deficiency even if iron studies are equivocal 3
• Long-term iron therapy may be appropriate if the cause is unknown or irreversible after complete evaluation 3