The normal appendix is located in the lower right abdomen below the umbilicus. The appendix is a thin strip of tubular structure that leads to the cecum at one end and is connected to the cecum. Normally, the appendix is located at the anterior end of the cecum, but some of them are found at the posterior end of the cecum, and some of them can even pass through the posterior end of the cecum and go behind the peritoneum, so that in some surgeries, the appendix cannot be found after entering, and even the retroperitoneum has to be opened to find the appendix. The structure of the appendix is also variable. With the change of inflammation, some local abscesses are formed, and the appendix may not be visible after entering, and sometimes the appendix may melt away and form a large abscess cavity, and there is also a congenital variation of the appendix extending from the retroperitoneum up to the subhepatic area, which is not necessarily located at the posterior end of the cecum, but may be located in the ascending colon. However, it is also encountered in clinical practice, so when you see lower abdominal pain, sometimes right lower abdominal pain, right upper middle abdominal pain, if there are no other factors, you should also consider whether there is an ectopic appendix causing appendicitis.