Objective To evaluate the diagnostic value of ultrasound in chronic appendicitis. Methods A retrospective analysis was conducted on the ultrasound imaging features of the appendixes in 68 patients with chronic appendicitis (chronic appendicitis group) confirmed by pathological results at the Affiliated Hospital of Inner Mongolia Medical University from January 2023 to December 2024,as well as 85 healthy volunteers (normal appendix group) of different ages with no history of abdominal pain during the same period.Multivariate Logistic regression was employed to investigate the sensitivity and specificity of different variables in diagnosing chronic appendicitis. Results The chronic appendicitis group had higher appendix diameter (Z=-8.47,P<0.001),unilateral wall thickness (Z=-7.16,P<0.001),and submucosal thickness (Z=-9.73,P<0.001) than the normal appendix group.Appendix diameter (OR=3.11,95%CI=1.37-7.02,P=0.006) and submucosal thickness (OR=5 492.73,95%CI=89.53-336 984.13,P<0.001) were identified as independent factors for diagnosing chronic appendicitis,while gender,age,unilateral wall thickness,and intraluminal conditions had no significant impact on the diagnosis of chronic appendicitis (all P>0.05).When appendix diameter combined with submucosal thickness was used as a joint diagnostic indicator,the model demonstrated the best performance,with the sensitivity of 92.65%,the specificity of 97.65%,and the accuracy increasing to 95.42%. Conclusion The combined use of appendix diameter and submucosal thickness can significantly improve the accuracy,specificity,and reliability of ultrasound in diagnosing chronic appendicitis.