The Case of the Lime-green Stool: A Case Report and Review of Occult Blood Testing in the Emergency Department

Introduction: Food dyes mimicking gastrointestinal (GI) hemorrhage have been described in literature. However, reports of food additives causing melanotic stools and falsely positive fecal occult blood tests (FOBT) are uncommon in literature.Case Report: We present a case of a 93-year-old with FOBT positive melanotic stool, felt to be falsely positive due to food additives.Conclusion: Evaluation for GI bleeding accounts for 0.3% of yearly visits to the emergency department (ED).1 While FOBT is commonly used, its clinical validity in the ED is not supported by guidelines. We showcase the limitations of the FOBT and review the causes of false positive FOBT.