Is routine pathological analysis of perianal fistula specimen necessary in diagnosis of crohn's disease?

Background: Crohn's disease causes recurrent and complex perianal fistulas. Although the prevalence of it is up to 30%, the common cause of perianal fistula is thought to be the crypto-glandular theory. Surgeons send perianal fistula specimens for histopathological analysis; however, it is unclear whether such practices should be performed routinely. Objective: Evaluating the utility of routine histopathology on perianal fistula specimens during surgery to exclude the diagnosis of Crohn's disease. Design: Multicenter retrospective study was conducted from January 2012 to October 2018 on patients who underwent surgery for perianal fistula and specimen sent for histology. Setting: Metropolitan tertiary referral center in Melbourne, Australia. Patients and Methods: 105 patients who underwent 124 anal fistula procedures and their perianal fistula specimens sent for histopathological analysis were selected from the medical database. Medical and pathology reports were analyzed and data were reviewed by a second author for consistency. Sample Size: 105 patients, 124 procedures. Main Outcome Measures: Histopathological results suspicious for Crohn's disease and endoscopic examination results to confirm Crohn's disease. Results: 41 together, 124 perianal fistula specimens were collected from 105 patients. The male to female ratio was 2.9:1 and the average age was 43.6 years. Nonspecific inflammation was seen in 121 (97.5%) specimens. Three specimens had granulomatous inflammation of which, only two (1.6%) had Crohn's disease confirmed on endoscopic biopsy of the terminal ileum. In 15 patients with Crohn's disease, none of the 19 specimens sent for histology demonstrated histopathological features of Crohn's disease. Conclusion: Routine histopathological analyses of perianal fistula specimens provide limited clinical value. Clinicians should selectively send specimens for histopathological analysis to limit the use of resources. Limitations: Retrospective study. Not all perianal fistula specimens were routinely sent for the analysis. Data prior to 2012 was not collected as we are limited by an electronic database which was commenced in 2012. Conflict of Interest: None.