排便作为人体的正常生理行为与诸多肛肠良性疾病密切相关，患者的“便血、疼痛、脱出”等症状往往伴随排便动作发生。迄今为止，国内外对排便过程的研究多集中于粪便的类型、排便时肛门直肠的形态结构变化及肛门直肠压力等方面，而有关粪便的密度、粘度、排便速度以及粪便对直肠肛管的力学行为特征尚无相关报道。本项目以正常人为研究对象，把粪便的物性参数及排便动作肛管直肠受到的应力变化作为研究切入点，结合体位因素，运用力学模拟分析排便过程的力学变化，将临床实验（粪便密度、排便速度、排粪造影、肛门直肠压力、臀部几何特性）和力学实验（粪便粘性系数、肛管弹性模量）相结合，明确正常排便过程中直肠肛管组织受到粪便作用的生物力学特征，归纳排便过程的定量刻画指标集，从而建立正常人排便动作的生物力学模型，可为日后研究排便过程同肛肠良性疾病的发病和防治提供客观标准，为非药物疗法干预调节肛肠良性疾病提出个体化指导方案。

Though defecation is a normal physiological behavior of the human being, it accompanies with many benign anorectal diseases, Symptoms like “bleeding, pain and prolapse” always happen during defecation. So far studies of defecate process are mainly keen on Bristol Stool Scale, defecography and anorectal manometery, while research including density and viscosity of fecal and mechanical behaviors of the feces on anorectal canal has not been reported yet. This project will focus on the fecal physical properties and stress variance of anorectal canal combined with defecated posture of normal volunteers to analysis mechanical changes of defecation. We will use clinical experiment (stool density, defecate speed,defecography, anorectal manometry, geometry properties of hip) and mechanical experiment (fecal viscosity and elastic modulus of anorectal canal) to explain the biomechanical characteristics and quantitative induction of normal defecate process. Then we can establish biomechanical model of normal defecation of human being, which can be applied as the baseline to study the relationship between benign anorectal diseases and biomechanical characterizes of defecation in the future.