肛瘘是一种常见的肛肠疾病，近年来其症情日趋复杂难愈，严重影响患者生活质量。如何进一步明确其病因，预防其发生，阻止其复杂化的趋势，是肛瘘研究领域的新方向。究其病因，中医认为其主要病因为“湿热”与“虚”，这与患者的体质、饮食排便习惯密不可分。但目前国内外缺乏其流行病学及病因学的研究。本次研究以上海市单纯性肛瘘及复杂性肛瘘患者为研究对象，采用描述性横断面设计，运用国际通用量表和自定义问卷收集社会人口学、中医证/症候、中医体质分型、兼夹疾病、饮食习惯、排便情况、初期脓肿情况等流行病学数据；同时检测患者血液、尿液及细胞免疫指标。旨在明确肛瘘的致病因素、高危人群、及中医辨证特点，探讨发病原因与及细胞免疫的关系。同期采集患者血样及肛瘘DNA标本，为后续遗传因素系列研究，并最终建立肛瘘流行病学资料库及生物样本库奠定基础。为预防和控制该病以及制定相应的公共卫生策略提供依据。

Anal fistula is a common and difficult-to-heal anorectal disease. From the perspective of traditional Chinese medicine (TCM), “dampness-heat” and “deficiency” are the primary causes of anal fistula and this disease is closely related to patients’ constitution, diet habits, and defecation pattern. Anal fistula has become increasingly complicated with substantially adverse impacts on patients’ quality of life in recent years. As such, more research is required to further identify the etiology of anal fistula and thus prevent its occurrence and progression. However, there has been no epidemiology and etiology research on this important healthcare topic worldwide. To address the research gap, this descriptive cross-sectional study is to employ internationally applied and self-designed survey questionnaires to collect data among simple and complex anal fistula patients in Shanghai, focusing upon the information on social-demography, TCM syndrome/symptoms, TCM constitution type, accompanied diseases, diet habits, defecation pattern, early abscess situation, and other associated factors. In addition, patients’ blood, urine, and cellular immune indicators are also assessed for eventually investigating the etiological factors, risky population, and TCM syndromes of anal fistula. The collected blood and DNA samples of anal fistula patients will be useful for the construction of future anal fistula database and biobank, and provide evidence for healthcare policy-making in the area of anal fistula.