Abstract: Objective To investigate the clinical effects of mesalazine combined with hyperbaric oxygen (HBO) on ulcerative colitis (UC) and the changes in serum immunological indexes.Methods A retrospective analysis was made of the 120 UC patients admitted to the Department of Gastroenterology,Chongming Branch of Xinhua Hospital Affiliated to Shanghai Jiaotong University from January 2014 to January 2018.The patients were randomly divided into the observation group and the control group,each consisting of 60 patients.The control group was treated with mesalazine enteric-coated tablets on the basis of routine treatment,while the observation group was supplemented with HBO therapy in addition to the treatment received by the control group.After 3 courses of treatment,clinical effective rate and UC activity indexes were compared between the 2 groups.The serum levels of tumor necrosis factor-a (TNF-a),interleukins-2,4,6 and 10 were detected by enzyme-linked immunosorbent assay (ELISA),the serum level of superoxide dismutase (SOD) was detected by nitrite method and that of malondialdehyde (MAD) was assayed by thiobarbituric acid colorimetty,the levels of immunoglobulins (IgA,IgG,IgM) were determined by agar immunoassay,and the level of asymmetric dimethylarginine (ADMA) was detected by fluorescence derivation and capillary electrophoresis.The above indicators were evaluated upon completion of the treatment.Results The total effective rate of the observation group (93.3%) was significantly higher than that of the control group (76.6%) (P < 0.05),and the UC activity scores of the observation group were significantly lower than those of the control group (P < 0.01).After treatment,statistical significance could be seen in the levels of serum IgA and IgG in the observation group,as compared with those before treatment and those of the control group after treatment (P < 0.05).Statistical significance could also be noticed in the levels of serum IL-2,IL-6 and IL-10 in the observation group,as compared with those before treatment and those of the control group after treatment (P <0.05 or P <0.01).After treatment,there was also statistical significance in the serum levels of SOD and MAD in the observation group,as compared with those before treatment and those of the control group after treatment (P <0.05 or P < 0.01).Following treatment,statistical significance could be noted in the serum levels of TNF-a and ADMA in the 2 groups,as compared with those before treatment and those of the control group after treatment (P < 0.05 or P < 0.01).Conclusion Mesalazine combined with HBO could alleviate colonic tissue injury,inhibit mucosal immune response,reduce oxygen free radical level,accelerate intestinal mucosal repair and improve clinical efficacy in UC patients.For this reason,it is worth further clinical promotion and application.