Temporal and Sequential Relationships Between Perianal and Severe Ileal Crohn's, Both as Strong Representations of Crohn's Fistulizing Phenotypes

Abstract Introduction/Objective Most cases of inflammatory bowel disease can be categorized as ulcerative colitis(UC) or Crohn’s disease(CD) on the basis of clinical profile, disease distribution, imaging and endoscopic findings, and pathological abnormalities. Ileal CD with deep fissuring ulcers and imminent or overt fistulae represents a specific phenotype. A similar fistulizing phenotype is indicated by complex perianal CD which shows fistulous tracts between rectum and perineum. We followed CD patients with either disease to discover if both fistulizing phenotypes occurred concurrently or with any predictable sequence. Methods/Case Report From our databases, we collected 21 patients with complex perianal CD(M:F=7:14, ages 23-80) and 19 patients with fistulizing ileal CD(M:F=11:8, ages 10-67) and followed them for a period of up to 16 years(2005-2021). Our purpose was to discover if both fistulizing phenotypes occurred in the same patients, and if so, was it concurrent or in any sequence, and to find the strength of the clinical diagnosis of CD when one or both phenotypes presented in a patient. Results (if a Case Study enter NA) Concurrent occurrence of perianal and ileal CD was the most common(6/21 perianal & 8/19 ileal cases: total 35%). When patients first presented with perianal CD, they had an equal chance of not manifesting ileal phenotype(5/21) or manifesting it earlier(5/21: average of 5 years earlier) or later(5/21: average of 2.5 years later). However, when patients first presented with ileal CD, they had a strong possibility of having manifested perianal disease in the past(10/21 or 48%: average of 5 years), when it was overlooked as a strong indicator of Crohn’s. Perianal CD was considered a strong clinical diagnosis of Crohn’s but only when it occurred concurrently or was preceded by ileal CD. Fistulizing Ileal CD was considered a strong clinical diagnosis of Crohn’s and most cases had prior perianal CD. Conclusion Both perianal and severe ileal CDs are fistulizing phenotypes that are strong indicators of Crohn’s and occur concurrently in 35% of cases. When followed for a long period, both phenotypes manifest in most patients when they have severe fistulizing disease. Perianal CD appears to precede ileal CD by an average of 5 years. While fistulizing ileal CD is clinically unequivocally diagnosed as Crohn’s, perianal CD may be overlooked as Crohn’s, unless there is concurrent or prior ileal CD.