"Xuanfu",as the microscopic structure in TCM theory of visceral manifestations,spreads all over the human body.The microscopic pathological changes of acute ulcerative colitis are manifested as cryptic abscesses or even structural disorders of the colon.Its damp heat accumulates in the large intestine,and the pathogenic characteristics of the large intestine coincides with the concept of"Xuanfu"that likes opening and avoiding closing.The functions of the mechanical barrier and mucus barrier in the intestinal crypt are very similar to the characteristics of the"Xuanfu",which can provide morphological basis for the"Xuanfu"theory of the intestine.The method of clearing away and opening the"Xuanfu"can inhibit the"Xuanfu closed"state of the intestine caused by the accumulation of damp and heat,and promote the guiding role and theoretical support of the"Xuanfu-crypt"theory in the treatment of early crypt lesions of ulcerative colitis.