Endoscopic Diagnosis of Necator americanus Infection Presenting With Persistent Iron-Deficiency Anemia: Usefulness of Image-Enhanced Endoscopy and Capsule Endoscopy.

Necator americanus infection is now rare in developed countries but remains an important cause of iron-deficiency anemia and abdominal symptoms in individuals with relevant epidemiological backgrounds. A 59-year-old Filipino man with long-standing unexplained iron-deficiency anemia was admitted to our hospital for epigastric pain associated with choledocholithiasis. Although biliary enzymes improved after endoscopic treatment, his abdominal pain persisted. Subsequent gastrointestinal investigations, including upper gastrointestinal endoscopy, colonoscopy, and small-bowel capsule endoscopy, revealed multiple parasites distributed throughout the gastrointestinal tract. Image-enhanced endoscopy using narrow-band imaging clearly improved visualization of the parasites compared with conventional white-light imaging, facilitating their identification and endoscopic removal. Genetic analysis of the extracted worms confirmed N. americanus infection. The patient was treated with pyrantel pamoate, which resulted in the resolution of abdominal symptoms and improvement of iron-deficiency anemia. Follow-up stool examination confirmed eradication of the parasite. This case highlights the importance of considering hookworm infection in patients with persistent iron-deficiency anemia and abdominal pain, even in developed countries. In addition, image-enhanced endoscopy and capsule endoscopy are valuable diagnostic tools for detecting hookworms and assessing their distribution within the gastrointestinal tract.