What is the approach for a 28-year-old male with ongoing abdominal issues, mild anemia, and a positive Fecal Immunochemical Test (FIT) stool test?

Approach to 28-Year-Old Male with Positive FIT, Abdominal Symptoms, and Mild Anemia

This patient requires urgent colonoscopy within 30 days, as the combination of positive FIT, anemia, and abdominal symptoms constitutes high-risk features for early-onset colorectal cancer (eoCRC), and FIT should not be used to triage symptomatic patients—direct colonoscopy is mandatory. 1, 2

Immediate Management: Colonoscopy is Required

Proceed directly to colonoscopy without delay. The 2023 international guidelines for early-onset colorectal cancer explicitly state that FIT is not recommended for symptomatic patients because a positive result still requires colonoscopy, and delays are associated with increased risk of advanced-stage disease 1. Your patient has already tested positive, making colonoscopy non-negotiable.

Timing Requirements

• Schedule colonoscopy within 30 days of presentation with these alarming symptoms 1
• The maximum acceptable delay is 6 months, but aim for completion within 3 months 2
• Healthcare systems should achieve ≥95% of follow-up colonoscopies within 6 months of positive FIT 2

Why This Patient is High-Risk

Alarming Features Present

This patient has multiple high-risk features that mandate urgent evaluation:

• Unexplained iron deficiency anemia: This is classified as an alarming symptom requiring colonoscopy regardless of FIT status 1
• Positive FIT test: Has a high positive predictive value for significant neoplasia (40-47% for advanced neoplasia) 1
• Ongoing abdominal symptoms: While abdominal pain alone might be triaged with FIT, the combination with anemia elevates risk substantially 1
• Young age (28 years): Early-onset CRC patients are often diagnosed at later stages (III/IV), and diagnostic delays contribute to advanced disease 1

Evidence on Combined Risk Factors

The combination of positive FIT and iron deficiency anemia dramatically increases risk. Research shows that asymptomatic men with both positive FIT and IDA have a 28.6% prevalence of advanced colorectal neoplasia and 28.6% prevalence of CRC, compared to only 1.5% and 0.01% respectively in those with neither feature 3. In symptomatic patients with IDA, positive FIT increases the likelihood of finding a bleeding lesion to 79.2% versus 27.2% with negative FIT 4.

Colonoscopy Quality Requirements

The colonoscopy must be complete to the cecum and of high quality 1. This is critical because:

• Young patients with eoCRC often present with right-sided lesions
• Incomplete examination may miss synchronous lesions (occur in up to 3% of cases) 1
• High-quality examination allows simultaneous detection and removal of neoplasia 1

Additional Diagnostic Workup

While arranging colonoscopy, complete the following:

Pre-Colonoscopy Evaluation

• Confirm iron deficiency with iron studies: Serum ferritin is the single most useful marker, but check transferrin saturation if ferritin is equivocal 1
• Screen for celiac disease: Found in 3-5% of IDA cases; check tissue transglutaminase antibodies 1
• Urinalysis or urine microscopy: To exclude renal causes of anemia 1
• Complete blood count: Document baseline hemoglobin for comparison 1

Family History Assessment

Obtain detailed family history of all cancers, not just colorectal 1. This is crucial because:

• Hereditary syndromes are implicated in 13% of early-onset CRC 1
• 28% of eoCRC patients have a family history of CRC 1
• Having ≥2 first-degree relatives with CRC or ≥1 first-degree relative diagnosed before age 50-60 significantly increases risk 1

If Colonoscopy is Negative

Should the initial colonoscopy be negative but symptoms persist or anemia recurs:

Upper Endoscopy

• Perform gastroscopy to evaluate for upper GI sources of bleeding 1
• Obtain small bowel biopsies to exclude celiac disease if not already screened serologically 1

Small Bowel Evaluation

If bidirectional endoscopy is negative and IDA persists or recurs:

• Capsule endoscopy is the preferred test for small bowel examination (highly sensitive for mucosal lesions) 1
• CT/MR enterography may be considered as complementary investigations 1

Renal Tract Investigation

• Evaluate for renal causes if GI workup remains negative 1

Common Pitfalls to Avoid

Do NOT Repeat FIT Instead of Colonoscopy

Given the high positive predictive value of FIT for cancer detection, colonoscopy is mandatory when the test is positive—do not repeat FIT 1. This is a strong recommendation with moderate-quality evidence 1.

Do NOT Delay for "Low-Risk" Age

While this patient is young (28 years), early-onset CRC incidence is rising, and young patients often present with advanced-stage disease 1. Age should not be a reason to delay or avoid colonoscopy in the presence of alarming symptoms.

Do NOT Use FIT Results to Avoid Upper Endoscopy

A positive FIT with negative colonoscopy should not automatically prompt upper GI evaluation unless there is iron deficiency anemia or signs/symptoms of upper GI pathology 1. However, in this case, the patient has anemia, so upper endoscopy is indicated if colonoscopy is negative.

Iron Replacement Therapy

While diagnostic workup proceeds:

• Initiate iron replacement therapy for the anemia 1
• A good response (hemoglobin rise ≥10 g/L within 2 weeks) confirms absolute iron deficiency even if iron studies are equivocal 1
• Long-term iron therapy may be appropriate if the cause is unknown or irreversible after complete evaluation 1