An Incidental Finding in a Cecal Biopsy

Diagnosis

Intestinal spirochetosis.

Discussion

Spirochetes are seen in the colon of humans and animals and are probably transmitted by fecal-oral contamination.¹ They appear to be nonpathogenic in most cases in humans, however this is a controversial issue. Some studies have shown an association between intestinal spirochetosis (IS) and rectal bleeding or diarrhea and an improvement in symptoms with antibiotic treatment. Other studies have shown no association.²

The prevalence of IS in biopsies is approximately 1.5% in North America and England with increased prevalence in certain geographic regions (Scotland, Greece) and in the male homosexual population (28-36%). There also appears to be a higher prevalence in appendiceal biopsies. Endoscopy is usually normal and IS is an incidental histological finding. Some hypothesize that initial colonization causes symptoms with transition to an asymptomatic carrier state, comparable to Helicobacter pylori infection.¹

The organism responsible for IS has been recently identified as Serpulina pilosicoli, although previously it has been assumed to be Brachyspira aalborgi following the identification of this organism in one case of IS. Large microbiological studies of positive biopsies will have to be undertaken in order to confirm the identity of the organism(s) responsible for IS.²

The organisms are easily identified at the luminal border of gastrointestinal biopsies or specimens as a blue fringe adherent to the epithelial cells. A Warthin-Starry stain can be used to highlight the organisms and demonstrate their spiraled nature. TEM and/or SEM are not necessary for diagnosis however in this case, and others, has provided an opportunity to study the interaction of these organisms with the intestinal epithelial cells.³

At present, intestinal spirochetosis is a poorly understood entity with uncertain clinical significance. It is easily recognized by both light and electron microscopy when one is aware of its existence and characteristic appearance. In most cases the organism is discovered incidentally and requires no further therapy; however, in the presence of diarrhea and/or other symptoms a trial of metronidazole may prove to be effective.

References

1. Klaus JL, Riddell RH, Weinstein WM. Intestinal Spirochetosis. In: Gastrointestinal Pathology and Its Clinical Implications. New York: Igaku-Shoin; 1992. p.1046-9.
   
2. Trivett-Moore NL, Gilbert GL, Law CLH, Trott DJ, Hampson DJ. Isolation of Serpulina pilosicoli from rectal biopsy specimens showing evidence of intestinal spirochetosis. J Clin Micro 1998 Jan;36(1):261-5.
   
3. Guccion JG, Benator DA, Zeller J, Termanini B, Saini N. Intestinal spirochetosis and acquired immunodeficiency syndrome: ultrastructural studies of two cases. Ultrastructural Path 1995;19:15-22.

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