Introduction

Deep remission in complex perianal fistulizing Crohn’s disease (PFCD) is defined by both clinical and radiological remission. As the ultimate therapeutic goal for this condition, deep remission requires thorough assessment. MRI is the gold standard for evaluating complex perianal involvement.

Aims & Methods

Our aim was to identify baseline MRI factors linked to deep remission in PFCD and assess its impact on clinical outcomes. All patients with complex PFCD treated with anti-TNF-α agents at the gastroenterology department underwent baseline MRI and clinical evaluation. Radiological assessment included the number and type of fistula tracts (per Parks classification), presence/size of pelvic collections, horseshoe tracts (encircling more than 75% of the anal circumference), and rectal wall thickening. The Van Assche score was calculated. Follow-up MRIs were obtained only after clinical remission to assess radiological remission.

Results

Out of 105 patients, 80 were included in the study (male-to-female ratio: 1.33), with a mean age of 32.35 years. On average, patients had 1.7 fistula tracts (range: 1–6), with trans-sphincteric fistulas accounting for 65% of cases. Specific subtypes included ano-vulvar tracts in 8 women (9.5%), rectovaginal in 5 patients (6%), and anorectal tracts extending to the scrotum in 2 men (2.4%). Pelvic collections were present in 14 individuals (16.7%), averaging 23.8 mm in size. Horseshoe-shaped tracts were identified in 19 patients (22.6%), and rectal wall thickening greater than 3 mm was seen in 49 (58.3%). The mean Van Assche MRI score was 14.9. All patients underwent seton placement. The majority (88.1%) received infliximab, while the remainder were treated with adalimumab. Clinical remission was achieved after a mean of 5.8 months. Radiological remission occurred in 24 patients (28.6%). Presence of horseshoe tracts (p=0.013) and Van Assche scores more than 14 (p=0.027) were significantly associated with failure to reach radiological remission. These factors were confirmed as independent predictors by multivariate analysis. Among those who initially achieved radiological remission, 13 experienced recurrence during an average follow-up of 65.8 months. Radiological remission was associated with improved outcomes: recurrence-free survival rates were 81.3% at 1 year, 62.7% at 3 years, and 50.1% at 5 years, compared to 62.2%, 35.8%, and 23.2%, respectively, in patients with clinical remission but without radiological remission.

Conclusion

Deep remission was achieved in about one-third of PFCD patients following clinical remission. Horseshoe fistulas and Van Assche score more than 14 predict failure to reach this goal, correlating with worse long-term outcomes. These findings support the Top-Class classification designating such cases as unsuitable for curative repair, emphasizing symptom control instead.