Quantifying 18 F-Fluorodeoxyglucose Uptake in Perianal Fistulas on PET/CT: A Retrospective Analysis.

Rationale and Objectives: The use of ¹⁸ F-fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT) in assessing inflammatory diseases has shown significant promise. Uptake patterns in perianal fistulas, which may be an incidental finding on PET/CT, have not been purposefully studied. Our aim was to compare FDG uptake of perianal fistulas to that of the liver and anal canal in patients who underwent PET/CT for hematologic/oncologic diagnosis or staging.
Materials and Methods: We retrospectively identified patients who underwent FDG-PET/CT imaging between January 2011 and May 2023, where the report described a perianal fistula or abscess. PET/CTs of patients included in the study were retrospectively analyzed to record the maximum standardized uptake value (SUV _max ) of the fistula, abscess, anal canal, rectum, and liver. Fistula-to-liver and Fistula-to-anus SUV _max ratios were calculated. We statistically compared FDG activity among the fistula, liver, and anal canal. We also assessed FDG activity in patients with vs. without anorectal cancer, as well as across different St. James fistula grades.
Results: The study included 24 patients with identifiable fistulas. Fistula SUV _max (mean=10.8 ± 5.28) was significantly higher than both the liver (mean=3.09 ± 0.584, p < 0.0001) and the anal canal (mean=5.98 ± 2.63, p = 0.0005). Abscess fistula SUV _max was 15.8 ± 4.91. St. James grade 1 fistulas had significantly lower SUV _max compared to grades 2 and 4 (p = 0.0224 and p = 0.0295, respectively). No significant differences existed in SUV _max ratios between anorectal and non-anorectal cancer groups.
Conclusion: Perianal fistulas have increased FDG avidity with fistula SUV _max values that are significantly higher than the anal canal.
Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Dr. David H. Ballard reports a relationship with Takeda Pharmaceutical Company Limited that includes: funding grants. Dr. Parakkal Deepak reports a relationship with Janssen Pharmaceuticals Inc that includes: consulting or advisory and funding grants. Dr. Parakkal Deepak reports a relationship with Pfizer Inc that includes: consulting or advisory and funding grants. Dr. Parakkal Deepak reports a relationship with Bristol Myers Squibb Co that includes: consulting or advisory and funding grants. Dr. Parakkal Deepak reports a relationship with Boehringer Ingelheim Pharmaceuticals Inc that includes: consulting or advisory and funding grants. Dr. Parakkal Deepak reports a relationship with AbbVie Inc that includes: consulting or advisory and funding grants. Dr. Parakkal Deepak reports a relationship with CorEvitas LLC that includes: consulting or advisory. Dr. Parakkal Deepak reports a relationship with Takeda Pharmaceuticals USA Inc that includes: consulting or advisory and funding grants. Dr. Parakkal Deepak reports a relationship with Sandoz Inc that includes: consulting or advisory. Dr. Parakkal Deepak reports a relationship with Landos Biopharma that includes: funding grants. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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