Supplementary Material for: Clinical features and short-term disease progression of asymptomatic perianal fistulizing Crohn’s disease

Introduction
Anal imaging improves the diagnosis of perianal diseases in Crohn’s disease (CD) patients, especially those with no perianal symptoms. However, the clinical characteristics and outcomes of CD patients with asymptomatic perianal fistula are unknown. This study aims to explore the prevalence and clinical course of Chinese CD patients with asymptomatic perianal fistula in a hospital-based cohort.
Methods
We performed a retrospective cohort study of consecutive hospitalized patients with newly diagnosed CD in China. Asymptomatic perianal fistula patients with CD were defined as those who exhibited fistula tracts on magnetic resonance imaging scans, absence of reported perianal symptoms or any prior history of perianal fistula. Their clinical features and prognosis were reviewed and analyzed.
Results
Among 376 patients who underwent anal imaging, 93 (24.73%) had asymptomatic perianal fistula, 187 (49.73%) had symptomatic perianal fistula, and 67 patients (17.82%) showed no perianal involvement. There were significant differences among patients without perianal lesions, patients with symptomatic perianal fistula, and patients with asymptomatic perianal fistula in the proportion of male sex (49.25% vs. 84.49% vs. 64.52%, respectively; p<0.001), age at diagnosis (median 32.00 vs. 26.00 vs. 24.00, p<0.01), disease location (p<0.05), and laboratory examination. Patients with asymptomatic perianal fistula had a higher cumulative incidence of abdominal surgery (p < 0.001) and intestinal obstruction (p < 0.05).
Conclusion
Patients with asymptomatic perianal fistulas account for a certain proportion of CD patients at diagnosis, with a higher proportion of stricturing behavior and cumulative incidence of intestinal obstruction and CD-related bowel surgery.

引言
肛门影像学检查可提升克罗恩病（Crohn’s disease, CD）患者肛周疾病的诊断效能，尤其针对无肛周症状的患者。然而，伴无症状肛周瘘（asymptomatic perianal fistula）的CD患者的临床特征与转归仍未明确。本研究旨在基于一项医院队列，探究中国CD患者无症状肛周瘘的患病率及临床病程。
方法
本研究针对中国连续纳入的新发CD住院患者开展回顾性队列研究。将经磁共振成像（magnetic resonance imaging）扫描检出瘘管、无肛周症状报告且无肛周瘘（perianal fistula）既往史的CD患者定义为无症状肛周瘘（asymptomatic perianal fistula）患者。对该类患者的临床特征与预后进行回顾分析。
结果
在接受肛门影像学检查的376例患者中，93例（24.73%）伴无症状肛周瘘（asymptomatic perianal fistula），187例（49.73%）伴症状性肛周瘘（symptomatic perianal fistula），另有67例（17.82%）无肛周受累。无肛周病变患者、症状性肛周瘘患者及无症状肛周瘘患者在男性占比（分别为49.25%、84.49%、64.52%；p<0.001）、诊断时年龄（中位数分别为32.00、26.00、24.00，p<0.01）、病变部位（p<0.05）及实验室检查结果方面均存在显著差异。无症状肛周瘘患者的腹部手术累积发生率（p<0.001）与肠梗阻累积发生率（p<0.05）均更高。
结论
确诊时，伴无症状肛周瘘的CD患者占一定比例，该类患者的狭窄型表型（stricturing behavior）占比更高，肠梗阻及CD相关肠道手术的累积发生率也更高。