It is believed that the latent dampness-heat pathogen constitutes the core pathogenesis of ulcerative colitis （UC）， characterized by the pattern of "lurking in the three

yin

（

taiyin， shaoyin， jueyin

） and emerging from the three

yang

（t

aiyang， shaoyang， yangming

）"， with a tendency to transform into fire. The pathogenic evolution can be delineated into three stages， the latent stage manifesting as

taiyin

deficiency with healthy

qi

deficiency and lingering pathogen， allowing dampness-heat to lurk internally； the active stage involving pathogen penetrating the three

yang

， with dampness-heat externally erupting， leading to putrefaction of flesh and impairment of blood； the prolonged stage pertaining to

jueyin

invading the collaterals， with dampness-heat and static blood binding together， culminating in the formation of abdominal masses. The therapeutic approach adopts the strategy of pathogen-expelling by stage. During the latent stage， therapy focuses on fortifying the spleen and promoting pathogens， concurrently clearing and transforming， aiming at eradicating the latent pathogens， using modified

Qiwei Baizhu Powder

（七味白术散） or self-prescribed

Zhaqu Jianpi Decoction

（楂曲健脾汤）. During the active stage， emphasis is placed on clearing and resol-ving pathogens， promoting stagnation and unblocking obstruction， primarily focusing on providing an outlet for pathogens， using modified

Zhishi Daozhi Decoction

（枳实导滞汤） as the main formula. For the prolonged stage involving

jueyin

invading the collaterals， ingredients that resolve stasis and unblock c

ollaterals， such as Biejia （

Lawsonia inermis

） and Shuizhi （

Cucumis melo

）， are often prescribed.