A prospective cohort study of the rectal microbiome in patients with suspected appendicitis

PURPOSE: Diagnosing appendicitis is difficult. An infectious origin has been proposed, therefore signals from the microbiome could be a potential diagnostic measure. The aim was to evaluate the diagnostic potential of the rectal microbiome in patients with suspected appendicitis.

METHODS: We included adult Danish patients with suspected appendicitis undergoing appendectomy in a prospective, observational cohort study. Patients were first grouped as patients with and without appendicitis according to histopathological findings, and second, as having uncomplicated or complicated appendicitis according to the surgical report. Rectal swabs were analysed with shotgun metagenomics. The outcomes were alpha diversity, beta diversity, and differential abundance of bacteria.

RESULTS: Rectal swabs from 220 patients were analysed: 49 patients without appendicitis, 111 patients with uncomplicated and 60 patients with complicated appendicitis, respectively. Across all groups, both the alpha and beta diversity were similar. The relative abundance of bacterial genera and species was also similar across all groups. Thus, the three groups of patients had similar rectal microbiomes.

CONCLUSION: The rectal microbiome in adult patients with suspected appendicitis was similar and does not seem to have the potential to be used to diagnose neither appendicitis nor the severity of appendicitis preoperatively.

TRIAL REGISTRATION: NCT03349814 (clinicaltrials.gov).