Objective To observe clinical effects and possible mechanism of Modified Pulsatilla Decoction for enema treating acute period of ulcerative colitis of left hemicolon type. Methods Totally 34 cases of patients with acute period of ulcerative colitis of left hemicolon type were randomly divided into treatment group and control group

with 17 cases in each group. Gave treatment group Modified Pulsatilla Decoction for retention enema

1 dose per day

once every day. Gave control group Sulfasalazine for enema

1 g each time

twice per day. Treatment course was 45 days both. Compared Chinese medicine syndrome scores and colon mucosa lesion of the two groups before and after treatment. Tested the expression of intestinal mucosa interleukin-8（ IL-8）

and evaluated the treatment effect of Chinese medicine syndrome. Results Symptom scores and aggregate scores of diarrhea

bloody purulent stool

abdominal pain

abdominal distention

tenesmus

anorexia and feeble of two groups after treatment decreased compared with those before treatment（ P < 0. 05 or P < 0. 01）. Symptom scores and aggregate scores of diarrhea

bloody purulent stool

abdominal pain of treatment group after treatment remarkably decreased compared with those of control group（ P < 0. 05）. Total effective rate of Chinese medicine syndrome of treatment group and control group was respectively 94. 11% and 76. 47%. The difference was statistically significant（ P < 0. 05）. Microscopy colon mucosa lesion score and expression of IL-8 all remarkably improved compared with those before treatment（ P < 0. 01）. Colon mucosa lesion score of treatment group was remarkably lower than that of control group（ P < 0. 05）. Difference of expressional intensity of IL-8 was not statistically significant compared with that of control group（ P > 0. 05）. Conclusion Modified Pulsatilla Decoction for enema could improve clinical symptom and repair mucosal tissue of patients with acute period of ulcerative colitis of left hemicolon type. Its mechanism may be related to down-regulating expression of IL-8 in intestinal mucosa.