A case of parasite invasion of the intestinal tract: a missed diagnosis in irritable bowel syndrome.

Irritable bowel syndrome (IBS) is a gastrointestinal disorder characterized by chronic abdominal pain and altered bowel habits in the absence of any organic cause. As the clinical manifestations are very diverse and associated with nonspecific symptoms, research seeking to identify organic causes to rule out IBS and to enable differential diagnosis is required. A 24-year-old man was referred to our hospital for specialized management of IBS. He had a 7-month history of intermittent epigastric and lower abdominal pain. On the basis of clinical examination, he was diagnosed with IBS and administered medication at a primary clinic. However, his symptoms did not improve after treatment. We performed capsule endoscopy at our hospital and identified a parasite (Ancylostoma duodenale) in the proximal jejunum. We therefore report a case of parasitic infection found by additional examination while evaluating symptoms associated with a previous diagnosis of refractory IBS.