The appendiceal fossa is the normal opening of the appendix found during colonoscopy and is a normal physiologic structure. The main causes of appendiceal fossa bulging include appendicitis, localized polyps and tumors. 1. Appendicitis: Whether it is acute or chronic appendicitis, the mucosal edema and thickening will lead to bulging lesions, some of which will be accompanied by purulent lesions. 2. Localized polyps: localized bulging of the appendiceal fossa may also be caused by polyps, which are closely related to local tissue proliferation, and may also appear under the influence of inflammatory stimuli. 3. Tumor: Tumor-like lesions in the surrounding mucosal cells can also lead to changes in the corresponding conditions, which will gradually increase in size. If you find the bulge of appendiceal fossa, you need to do pathological biopsy to determine the specific cause of the disease and then do standardized treatment.