EP292 - Crohn's disease combined with complex anal fistula and anorectal stenosis

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Purpose/Background: Perianal lesions are a common manifestation of Crohn's disease. The treatment of perianal Crohn's disease often requires a multidisciplinary approach that combines both surgical and pharmacologic therapies. At present, surgery with biological agent has achieved better clinical results. Recurrent complex anal fistula with local fistulas penetrating the perianal tissue can easily cause anorectal stenosis due to tissue inflammation and scar formation. Hence, formulating an effective treatment plan and deciding the proper timing of treatment are the key to the management of Crohn's disease complicated with anal fistula and anorectal stenosis.

Methods/Interventions: A 36-year-old male patient underwent surgery for perianal abscess in February 2023. but perianal symptoms recurred and the patient was further diagnosed with Crohn's disease. He received Infliximab for treatment. On July 2023 and perianal symptoms with defecation disorders recurred in July 2024.
At the time of the patient's visit, the physician responsible for the initial examination found anorectal stenosis, the specific anorectal conditions of the patient were as follows: a hyperplastic bulge formed at the anal opening at the 1 o'clock position, a narrow ring (approximately 0.5 cm in diameter and 1 cm wide at the top and bottom) with mucosal erosions appeared 1.5 cm above the dentate line. There was a stenosis reaching 2 cm above the anorectal ring but the condition was less severe than the narrow ring. An indentation at the dentate line at the 9 o'clock position was observed and formed an upward intersphincteric fistula.
Subsequently, the patient underwent surgical treatment. The external opening of the anal fistula and the hyperplasia at the anal opening were removed during the surgery. The narrowed part was loosened along the muscle at o'clock 1, 4-5 positions using an ultrasonic knife. Next, a resistance-free anal endoscope was inserted to help perform drainage between the fistulas. Postoperative pathology showed a large number of inflammatory cells near the fistula and accumulation of abundant fibroblasts in the narrowed tissue. Evaluation on the patients’ blood drug concentration of Infliximab demonstrated a reduced blood drug concentration of the drug, showing an inability to produce enough anti-antibodies to reach a therapeutic effect on the patient. Therefore, one week after surgery the patient was treated with a single change of the IV administration of biologic ustekinumab (390 mg).

Results/Outcomes: After the surgery, the wound condition stabilized and the patient was discharged. The dressing was changed regularly in the outpatient department and the patient was followed up for 6 weeks. The wound was completely healed and anal dilation continued for 3 months. Finally, the patient's perianal conditions became normal, with smooth bowel movements and no recurrence tendency. The preoperative CDAI, PDAI, and Wexner scores for patients were 183.7, 14, and 17, and postoperative scores were 115.54, 0, and 0, respectively.

Conclusion/Discussion: Crohn's disease with perianal complex fistula causing anorectal stenosis does not mean it is irreversible, however, the physician needs to carefully diagnose and evaluate the conditions of a patient in order to develop an optimal treatment plan to avoid adverse effects to the patient.