What are the next steps for a patient with occult blood and Blastocystis (B.) hominis in their feces?

Management of Occult Blood and Blastocystis hominis in Feces

Patients with occult blood in stool and Blastocystis hominis should undergo colonoscopy to rule out colorectal neoplasia, as the presence of occult blood requires thorough evaluation regardless of the B. hominis finding.

Evaluation of Occult Blood in Stool

Initial Assessment

• Occult blood in stool is a significant finding that requires proper evaluation regardless of the presence of B. hominis
• According to the American Gastroenterological Association guidelines, patients with a positive fecal occult blood test (FOBT) should be followed up with colonoscopy 1
• The presence of occult blood should not be attributed to B. hominis without adequate colonic evaluation

Diagnostic Algorithm

1. Colonoscopy: First-line evaluation for any patient with positive FOBT

   • Colonoscopy is substantially more accurate than double contrast barium enemas for detection of both small cancers and adenomas 1
   • If complete colonoscopy cannot be performed, sigmoidoscopy with air-contrast barium enema is the next best alternative 2

2. Upper Endoscopy (EGD): Consider if colonoscopy is negative and occult bleeding persists

   • Commonly overlooked lesions in upper GI tract include Cameron's erosions, fundic varices, peptic ulcer disease, angioectasias, and Dieulafoy's lesion 1

3. Further Evaluation: If both colonoscopy and EGD are negative:

   • For patients with occult GI blood loss and iron deficiency anemia, capsule endoscopy should be considered 1
   • Age of patient should guide aggressiveness of workup (more aggressive in younger patients) 1

Approach to Blastocystis hominis

Clinical Significance

• The pathogenicity of B. hominis remains controversial 1
• B. hominis may be clinically relevant if symptoms persist in the absence of other pathogens 1
• Symptoms commonly attributed to B. hominis infection include:
  • Abdominal pain (most common - 87.9%)
  • Constipation (32.2%)
  • Diarrhea (23.4%)
  • Alternating diarrhea and constipation (14.5%) 3

Management Considerations

• Treatment for B. hominis is debated and should be considered only after ruling out other causes of symptoms 4
• If treatment is warranted after excluding other pathologies:
  • Metronidazole (500-1000 mg/day for 7-10 days) has been shown to be effective 3
  • Treatment should be reserved for symptomatic patients with persistent symptoms and large numbers of B. hominis in repeated stool specimens 3

Important Considerations and Pitfalls

Avoid These Common Mistakes

1. Do not assume B. hominis is causing the occult blood

   • Endoscopic studies have typically not shown evidence of significant intestinal inflammation in B. hominis infection 5

2. Do not repeat FOBT if positive

   • Nearly one in three physicians inappropriately repeat FOBT if the first test is positive 1
   • This delays proper diagnostic evaluation

3. Do not attribute fecal occult blood to hemorrhoids without proper evaluation

   • Hemorrhoids alone do not cause a positive result with a stool guaiac test 1

Special Populations

• Patients with immunocompromise or malignancy may be more susceptible to B. hominis as an opportunistic infection 6
• In patients with underlying diseases, especially malignancy or chronic diseases, B. hominis infection may be more clinically significant 6

Follow-up

• Monitor for resolution of symptoms after treatment
• If occult blood persists after negative colonoscopy and treatment of B. hominis, consider:
  • Repeat testing for occult blood
  • Further evaluation of the small bowel
  • Evaluation for other causes of occult bleeding

Remember that the primary concern with occult blood in stool is the possibility of colorectal neoplasia, which requires thorough evaluation regardless of the presence of B. hominis.