Bridging clinical and pathological perspectives in the diagnosis of intestinal spirochetosis

Intestinal spirochetosis is a zoonotic infection caused by Brachyspira aalborgi or B. pilosicoli. It may present with nonspecific abdominal pain or diarrhea and can mimic irritable bowel syndrome. We retrospectively examined nine patients diagnosed with intestinal spirochetosis histopathologically between 2014 and 2024. All patients were middle-aged men, and the condition in 66.7% was incidentally identified in colorectal polypectomy specimens. Endoscopic findings were mostly nonspecific, with mild erythema or edema observed in 22.2% of patients. Five patients received metronidazole or amoxicillin, of whom three (60%) exhibited clinical improvement. Notably, the condition in 77.8% of cases was diagnosed by a single pathologist, suggesting variability in recognition. As spirochetes form a basophilic 2-3 μm fringe along the epithelial surface on hematoxylin and eosin staining, awareness among pathologists is crucial. Intestinal spirochetosis should be considered in patients presenting with irritable bowel syndrome-like symptoms, and active biopsy is recommended for definitive diagnosis.